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J Korean Dysphagia Soc 2021; 11(1): 43-51

Published online January 30, 2021 https://doi.org/10.34160/jkds.2021.11.1.006

Copyright © The Korean Dysphagia Society.

Effectiveness of Formal Dysphagia Screening for Stroke Patients

Mi Ran Yoo, M.D.1, Yoon Mok Chun, M.D.1, Kyoung Hyo Choi, M.D.1, Sun Uck Kwon, M.D.2, Eun-Jae Lee, M.D.2

1Department of Rehabilitation Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 2Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

Correspondence to:Kyoung Hyo Choi, Department of Rehabilitation Medicine, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea
Tel: +82-2-3010-3797, Fax: +82-2-3010-6964
E-mail: kyounghyochoi@gmail.com

Received: July 20, 2020; Revised: July 21, 2020; Accepted: August 28, 2020

Objective: Early identification of dysphagia after stroke helps in preventing aspiration pneumonia. However, data are limited regarding the effectiveness of formal dysphagia screening for reducing the risk of aspiration pneumonia. The current study evaluates the effectiveness of formal dysphagia screening in stroke patients, to prevent future episodes of aspiration pneumonia.
Methods: The stroke registry of a tertiary hospital was retrospectively reviewed. We compared clinical variables and the incidence of aspiration pneumonia of patients hospitalized between 2014 and 2015 after formal screening was implemented, and patients hospitalized in 2011 when no established dysphagia screening protocol was in place. Additionally, we identified the incidence of pneumonia according to stroke severity, and evaluated the association with results obtained for incidence of pneumonia and dysphagia screening.
Results: A total of 2,902 patients were identified to have suffered acute stroke (2,018 who underwent formal dysphagia screening; 884 without screening). Patients with formal dysphagia screening developed pneumonia less frequently than patients not administered screening (1.3% with formal screening vs. 3.4% no formal screening, P<0.001). Pneumonia was significantly lower in patients with moderate and severe stroke who underwent formal dysphagia screening. Furthermore, failure of the dysphagia screening test, presentation with severe dysarthria, and conditions where dysarthria could not be evaluated, were independent predictors of pneumonia among patients who underwent formal screening.
Conclusion: Our findings demonstrate the association of formal dysphagia screening with reduced risk of post- stroke aspiration pneumonia, and indicates the efficacy of the procedure in identifying patients at higher risk of contracting pneumonia.

Keywords: Dysphagia, Screening, Stroke, Pneumonia, Aspiration

Dysphagia after stroke is a common neurological symptom; 35-67% of acute stroke patients develop dysphagia1,2. Aspiration of food or oral secretions and dysfunction of the cough reflex in patients with dysphagia can lead to pneumonia. Stroke-associated pneumonia has been found to correlate with longer hospital stays, worse prognosis, and increased healthcare costs of stroke patients1 -5.

To prevent the above-mentioned problems caused by dysphagia in acute stroke patients, various met-hods can be utilized to identify dysphagia early. Met-hods for identifying dysphagia include dysphagia screening, which includes a swallowing test that can be conducted at the bedside or in–office, and more detailed dysphagia assessments, such as videofluoro-scopic swallowing study (VFSS) and fiberoptic endo-scopic examination of swallowing (FEES). Despite the effectiveness of these and other tests for identifying dysphagia, it is difficult to apply the above methods to all stroke patients due to limitations in manpower and cost, so dysphagia screening is often selectively applied to patients who are more likely to have dys-phagia3 -6.

Although it is not clear whether different methods of swallowing assessments reduce the risk of pneu-monia, disability, or death after stroke, the bedside screening test for dysphagia has been shown to effectively reduce pneumonia incidence rates when applied to patients with acute stroke6 -9.

Additionally, dysphagia screening before stroke patients begin oral intake has been recommended8. In several studies, implementation of dysphagia screening programs has been shown to reduce the incidence of pneumonia10,11. Moreover, the use of a formal dys-phagia screening protocol in a prospective 15-hospital study was reported to lead to a decrease in the in-cidence of pneumonia in stroke patients12.

Despite the recommendation of stroke manage-ment guideline8, the evidence level for recommen-dation is moderate grade, and insufficient evidence has been provided to establish that dysphagia screen-ing protocols effectively improve patient outcomes, such as by reducing pneumonia incidence8,13. In a recent study, no association between the use of dys-phagia screening and detailed dysphagia assessment and the risk of adverse outcomes including pneu-monia14.

We wanted to confirm whether the implementation of a formal dysphagia screening program where all acute stroke patients regardless of severity are screened can effectively reduce the incidence of pneumonia in stroke patients in our hospital. We also investigated the association between dysphagia screening result and incidence of pneumonia. The purpose of this study was to evaluate the effectiveness of formal dys-phagia screening in patients with stroke for the pre-vention of aspiration pneumonia.

1. Study design

We retrospectively identified stroke patients who were hospitalized in the neurology department of a single tertiary hospital. All stroke (ischemic stroke, hemorrhagic stroke) diagnoses were confirmed by admitting neurologists. Patients who died during the hospitalization period were excluded.

Dysphagia screening was defined as the use of a simple non-invasive bedside swallow screening test. Until 2012, dysphagia screenings were performed by admitting neurologists without an established dys-phagia screening protocol. Also, the tests have been only applied for stroke patients with higher stroke severity.

A standardized dysphagia screening protocol was implemented in our institution in 2014. Since then, all stroke patients underwent documented dysphagia screening within 48 hours of hospital admission by a trained speech-language pathologist (SLP). The pa-tients were checked for mental status, dysarthria, facial palsy, and tongue impairment or dysphonia. And a dry swallow test was first performed and then a wet swallow test where the patient was instructed to drink a small volume of water was performed. The formal dysphagia screening tests have been routinely performed in all stroke patients regardless of stroke severity since 2014.

We compared screening results and outcomes of stroke patients who underwent formal dysphagia screening (classified as the ‘formal screening group’ of patients who were hospitalized between 2014 and 2015) and those who did not receive formal dysphagia screening (classified as the ‘no formal screening group’ of patients who were hospitalized in 2011).

Stroke patients who underwent formal dysphagia screening were further categorized into those who passed or failed the test so that outcomes could be compared. If the patient failed to swallow or swal-lowed with choking, wet hoarseness or changes in breathing in a dry swallow test or wet swallow test, each test was evaluated as failed test. If the patient failed either the dry swallow test or the wet swallow test, the patient was categorized into the group who failed the test.

This study was approved by the center’s insti-tutional review board (S2017-1210-0003).

2. Data and outcome variables

Demographic variables included age, sex, stroke type, stroke severity score by the National Institutes of Health Stroke Scale (NIHSS), stroke risk factors (heart disease, diabetes mellitus, hypertension, dys-lipidemia), level of consciousness (alert, not alert), presentation with dysarthria and modified Rankin Scale on admission.

Initial NIHSS scores were categorized into three groups: mild (NIHSS 0-4), moderate (NIHSS 5-15), severe (NIHSS 16-42).

The outcome of interest was the incidence of radiographically confirmed aspiration pneumonia within 30 days of hospitalization.

3. Diagnosis of aspiration pneumonia

Aspiration pneumonia was confirmed when all of the following conditions were met: (1) the patient developed new-onset fever; (2) at the time of fever occurrence, pneumonia or aspiration pneumonia was recorded as the cause of fever in the medical record, including the progress notes and/or consultation notes; (3) piperacillin/tazobactam was administered at the time of fever occurrence; (4) abnormal lab findings such as leukopenia, leukocytosis, or elevated C-reactive protein were identified; and (5) definitive abnormal findings on chest radiographs were identi-fied within 30 days of hospitalization 15,16 .

Patients were excluded if they: (1) were transferred from another hospital after receiving antibiotics, (2) had another potential fever origin such as urinary tract infection or thrombophlebitis, (3) or were diag-nosed with community-acquired pneumonia rather than hospital-acquired pneumonia.

4. Statistical analysis

Categorical variables are presented as percentages and continuous or discrete variables are presented as means±standard deviations. To compare the charac-teristics and the outcome of interest, the Student’s t-test was used for continuous variables and Fisher’s exact test and the chi-squared test were used for categorical variables.

The association between clinical variables and incidence of aspiration pneumonia was assessed by univariate logistic regression analysis. For clinical variables with P values<0.1 were included in multi-variable models. All potentially significant variables were included in multivariate logistic regression analysis. Multiple logistic regression analysis with stepwise fashioned variable selection was used to identify variables that were independent predictors of incidence of aspiration pneumonia.

The primary analysis was used to evaluate asso-ciations between the use of formal dysphagia screen-ing on the outcome of aspiration pneumonia. We also calculated the proportion of patients who failed the screening test. For the secondary analysis, we used multiple logistic regression to identify the effect of failing screening on the odds of patients developing pneumonia, with adjustment of potential confounders.

All statistical analyses were performed using SPSS version 18.0 (IBM Inc., Armonk, NY, USA). Differ-ences were considered to be statistically significant when P<0.05.

Between January 1st, 2011, and December 31st, 2011, 901 patients who were admitted to the neuro-logy department for stroke without undergoing for-mal dysphagia screening were identified; the medical charts of 12 patients were irretrievable and 5 patients were excluded (1 was admitted for another reason and 4 died during the hospitalization period), leaving 884 patients to be included in the no formal screen-ing group. Between January 1st, 2014, and December 31st, 2015, 2,054 stroke patients were admitted and underwent formal dysphagia screening; the medical charts of 27 patients were irretrievable and 9 patients were excluded because they were admitted for an-other reason, leaving 2,018 patients in the formal screening group.(Fig. 1)

Figure 1. Flow diagram of patients did or did not undergo formal dysphagia screening.

Table 1 shows the comparison of clinical variables between patients who did or did not undergo formal dysphagia screening. There were no significant dif-ference in the distribution of sex, age, hypertension, diabetes mellitus status, cardiac disease, dyslipidemia, level of consciousness, presentation with dysarthria, mean NIHSS stroke severity score, and modified Rankin Scale at admission between the two groups. There was also no significant difference in the dis-tribution of NIHSS scores between the groups of patients who either did or did not undergo formal dysphagia screening. There were significantly more ischemic stroke patients in the formal dysphagia screening group than the no formal screening group (ischemic stroke with no formal screening, 90.4% (799/884) vs. formal screening, 93.6% (1,889/2,018); P=0.004). Meanwhile, when comparing the two groups, the proprotions of patients receiving non-oral diet was similar in both groups, but the proportion of patients receiving a modified diet was higher in the formal dysphagia screening group (non-oral diet with no formal screening, 17.6% (156/884) vs. formal screening, 16.2% (326/2018), modified diet with no formal screening, 28.9% (255/884) vs. formal screening, 38.5% (777/2,018); P=0.01).

Table 1 . Patient characteristics and incidence of pneumonia of patients who did or did not undergo formal dysphagia screening.

VariableNo formal screening group (n=884)Formal screening group (n=2018)P value
Sex
Female/Male340/544770/12480.88
Age64.7±12.965.2±13.60.24
Stroke type0.004*
Ischemic799 (90.4%)1889 (93.6%)
Hemorrhagic85 (9.6%)129 (6.4%)
Pneumonia30 (3.4%)26 (1.3%)<0.001*
Hypertension567 (64.1%)1246 (61.8%)0.23
Diabetes mellitus255 (28.8%)577 (28.6%)0.89
Cardiac disease273 (30.9%)588 (28.2%)0.35
Dyslipidemia221 (25.0%)497 (24.7%)0.84
Mental status0.74
Alert817 (92.4%)1872 (92.8%)
Non alert67 (7.6%)146 (7.2%)
Dysarthria0.73
None or mild607 (68.7%)1404 (69.6%)
Severe197 (22.3%)449 (22.2%)
Undeterminable80 (9.0%)165 (8.2%)
Mean NIHSS score5.08±5.45.24±5.10.20
NIHSS group0.66
Mild520 (58.8%)1159 (57.4%)
Moderate304 (34.4%)730 (36.1%)
Severe60 (6.8%)130 (6.4%)
mRS at admission0.51
0-2472 (53.4%)1104 (54.7%)
3-5412 (46.6%)914 (45.3%)
Diet recommendation0.01*
Non-oral156 (17.6%)326 (16.2%)
Modified diet255 (28.9%)777 (38.5%)
Regular diet473 (53.5%)915 (45.3%)

**P<0.05, statistically significant by Chi-squared test.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale.



The proportion of patients diagnosed with aspiration pneumonia was significantly lower in the formal dysphagia screening group than in the no formal screening group (1.3% (26/2,018) vs. 3.4% (30/884); P< 0.001).

The subgroup analysis of patients diagnosed with aspiration pneumonia according to NIHSS group is shown in Table 2. The proportion of patients diag-nosed with aspiration pneumonia was significantly lower in the formal dysphagia screening group when compared to the no formal screening group among moderate and severe stroke patients (moderate, no formal screening 5.4% vs. formal screening 1.5%, P=0.005; severe, no formal screening 4.2% vs. formal screening 2.6%; P=0.02); there was no significant difference in the proportions of mild stroke patients diagnosed with aspiration pneumonia between the two groups (no formal screening 0.3% vs. formal screening 0.2%; P=0.11).

Table 2 . Subgroup analysis of aspiration pneumonia incidence according to NIHSS group.

NIHSS groupNo formal screening group (n=884)Formal screening group (n=2018)P value
Mild (n=1679)5 (0.3%)10 (0.2%)0.11
Moderate (n=1033)17 (5.4%)16 (1.5%)0.005*
Severe (n=190)8 (4.2%)3 (2.6%)0.02**

*P<0.05, statistically significant by Chi-squared test, **P<0.05, statistically significant by Fisher’s exact test.

CXR: Chest X-ray, NIHSS: National Institutes of Health Stroke Scale.



Table 3 shows the univariate and multivariate logi-stic regression analyses of clinical variables associ-ated with aspiration pneumonia incidence. In the univariate logistic regression analysis, increasing age, level of consciousness (not alert), increasing stroke severity indicated by NIHSS score, modified Rankin Scale (mRS) at admission (3-5), presentation with dys-arthria (severe or undeterminable) and not receiving formal dysphagia screening were significantly associ-ated with the development of aspiration pneumonia. Not receiving formal dysphagia screening, lower level of function according to mRS scores, severe dys-arthria, and conditions where dysarthria cannot be evaluated were independent predictors of pneumonia in the multivariate regression analysis. The adjusted odds ratio of developing pneumonia in patients who underwent dysphagia screening was 0.36 (95% CI, 0.20 to 0.62).

Table 3 . Univariate and multivariate logistic regression analyses of clinical variables for association with aspiration pneumonia incidence.

Univariate analysisMultivariate analysis


OR95% CIP valueOR95% CIP value
Formal dysphagia screening0.370.22-0.63<0.000*0.360.20-0.62<0.000*
Age1.041.01-1.06<0.002*1.031.01-1.060.51
Sex (Male)0.890.51-1.540.67
Stroke type
IschemicReference-----
Hemorrhagic2.431.17-5.020.101.990.93-4.270.08
Mental status
AlertReference
Not alert5.523.03-10.1<0.000*1.180.58-2.410.65
Stroke severity (NIHSS)1.161.12-1.20<0.000*1.120.95-1.090.64
mRS at admission
0-2Reference-----
3-58.413.80-18.70<0.000*2.771.12-6.830.027*
Dysarthria
None or mildReference-----
Severe5.672.86-11.3<0.000*2.401.09-5.290.030*
Undeterminable12.96.30-26.5<0.000*2.850.99-8.190.049*

*P<0.05, statistically significant.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale, OR: odds ratio, CI: confidence interval.



Table 4 shows the baseline characteristics of pa-tients who either passed or failed the formal dyspha-gia screening test. Of the 2,018 patients who under-went formal dysphagia screening, 330 (16.4%) patients failed. Patients who failed screening had lower levels of consciousness, higher stroke severity, more fre-quent severe dysarthria, lower levels of function according to mRS scores, and were more often placed on a non-oral diet regime. The proportion of patients diagnosed with aspiration pneumonia was signifi-cantly higher in the patients who failed the dysphagia screening test than in the patients who passed the screening test (5.5% (4/330) vs. 0.4% (21/1688); P< 0.001).

Table 4 . Characteristics of patients who passed or failed the formal dysphagia screening test.

VariableDysphagia screening resultP value

PassFail
N (%)1,688 (83.6%)330 (16.4%)
Sex
Female/Male644/1,044126/2040.11
Age64.9±13.567.8±13.50.73
Stroke type0.23
Ischemic1,580 (93.9%)309 (92.1%)
Hemorrhagic108 (6.1%)21 (7.9%)
Pneumonia21 (0.4%)4 (5.5%)<0.001***
Hypertension1,042 (61.8%)204 (61.5%)0.92
Diabetes mellitus483 (29.2%)94 (25.5%)0.17
Cardiac disease492 (27.9%)96 (29.5%)0.60
Dyslipidemia416 (25.0%)81 (22.7%)0.38
Mental status
Not alert29 (1.7%)117 (35.5%)<0.001*
Mean NIHSS score3.75±3.3912.86±5.81<0.001**
NIHSS group<0.001*
Mild1,127 (66.8%)32 (9.7%)
Moderate546 (32.3%)183 (55.5%)
Severe15 (0.9%)115 (34.8%)
Dysarthria<0.001*
Severe314 (18.6%)135 (40.9%)
Undeterminable29 (1.7%)136 (41.2%)
mRS at admission<0.001*
3-5615 (36.4%)299 (90.6%)
Diet recommendation<0.001*
Non-oral2 (0.1%)326 (98.8%)
Modified diet773 (45.8%)4 (1.2%)

*P<0.05, statistically significant by Chi-squared test, ** P<0.05, statistically significant by Independent t-test, ***P<0.05, statis-tically significant by Fisher’s exact test.

NIHSS: National Institutes of Health Stroke Scale.



The univariate and multivariate logistic regression analyses for incidence of aspiration pneumonia of patients who underwent formal dysphagia screening are shown in Table 5. In the multivariate analysis, compared to those who passed screening, patients who failed screening had a significantly higher risk of pneumonia (5.5% vs. 0.4%; aOR, 5.53; 95% CI, 1.87- 16.4). Meanwhile, presentation with severe dysarthria and conditions where dysarthria could not be evalu-ated were found to be independent predictors of pneumonia in the multivariate regression analysis (22.2%; aOR, 4.48; 95% CI, 1.25-16.04; 8.2%; aOR, 1.50; 95% CI, 1.49-26.70, respectively).

Table 5 . Univariate and multivariate logistic regression analyses for incidence of aspiration pneumonia of patients who underwent routine dysphagia screening.

Univariate analysisMultivariate analysis


OR95% CIP valueOR95% CIP value
Sex (Male)0.890.51-1.540.67
Mental status
AlertReference-----
Not alert6.332.68-14.92<0.000*1.450.54-3.950.46
Stroke severity (NIHSS)1.161.12-1.20<0.000*0.970.88-1.080.61
mRS at admission
0-2Reference-----
3-58.413.80-18.70<0.000*1.250.30-5.270.76
Dysarthria
None or mildReference-----
Severe8.792.86-27.3<0.000*4.481.25-16.040.021*
Undeterminable12.906.30-36.5<0.000*1.501.49-26.700.012*
Results of dysphagia screen
PassReference-----
Fail13.855.74-33.450.000*5.531.87-16.40.002*

*P<0.05, statistically significant.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale, OR: odds ratio, CI: confidence interval.


We found that formal dysphagia screening is asso-ciated with lower risk of pneumonia in acute stroke patients when compared to acute stroke patients who did not undergo formal screening. Furthermore, among patients who underwent formal dysphagia screening, failing a dysphagia screening test, pre-sentation with severe dysarthria, and conditions where dysarthria cannot be evaluated were independent predictors of aspiration pneumonia.

Although many efforts have been made to imple-ment early screening for dysphagia in stroke patients, the adherence rates for dysphagia screening pro-tocols remains low, and some acute stroke units still have no formal screening protocol 12 . Meanwhile, there is insufficient evidence that the formal dys-phagia screening protocol effectively improves pa-tient outcomes.

Since 2014, our institution has followed a formal dysphagia screening protocol and it was performed in stroke patients of all severity levels including mild stroke at the time of admission to the neurology department. Before 2012, dysphagia screening was only used for patients with higher stroke severity levels. Notably, our study identified significantly fewer aspiration pneumonia cases among patients after formal dysphagia screening was implemented. We found that implementing the formal dysphagia screening reduced the incidence of aspiration pneumonia, even after adjusting for stroke severity.

These findings are similar to those of a previous study that also found that implementation of a formal dysphagia screening protocol was associated with reduced risk of pneumonia 12 . Other institutions have also implemented dysphagia screening programs with similar results. For example, Yeh et al. reported that dysphagia screening was associated with a decrease in stroke-associated pneumonia in all stroke patients after adjusting for factors such as stroke severity 17 . Judith et al. also found that the pneumonia rate was lower in patients who were screened with the formal dysphagia screening process and even after adjusting for stroke severity, and formal dysphagia screening was associated with fewer patients developing pneu-monia 12 .

Although patients with mild stroke are not com-pletely without risk for hospital-acquired pneumonia, they are often not considered for dysphagia screening because of their low risk of developing pneumonia. Joundi et al. reported that mild stroke patients were half as likely to be screened as moderate stroke pa-tients. However, patients with mild severity of stroke had moderate rates of dysphagia screening failure and substantial risk of complications after failing the screening test 18 .

The subgroup analysis according to stroke severity score found that aspiration pneumonia was less com-mon among patients with moderate and severe stroke severity after the formal dysphagia screening pro-gram was implemented. Although the difference was not significant, aspiration pneumonia was also some-what lower among mild stroke patients who under-went formal dysphagia screening when compared to patients who did not undergo formal screening.

Several studies have reported that failing the dys-phagia screening test is a powerful predictor of poor outcomes such as pneumonia 14,18 , more severe dis-ability 14,18 , and higher likelihood of the patient being discharged to a long-term care facility, even in pa-tients with mild strokes, who are less likely to be screened 18 . The current study also showed that failing the dysphagia screening test is a strong predictor of aspiration pneumonia occurrence, with an adjusted odds ratio of 5.53. Similar odds ratios have been re-ported in other studies as 4.71 18 and 3.00 14 . Further-more, not only failing a dysphagia screening test, presentation with severe dysarthria and conditions where dysarthria cannot be evaluated were also sig-nificant factor which were associated with the inci-dence of aspiration pneumonia of stroke patients who had underwent the formal dysphagia screening program. These findings were consistent with sug-gestions from several other studies 19,20 . Therefore, we suggest that formal dysphagia screening can be ef-fective to identify patients at higher risk such as failing the screening or presence of dysarthria for developing poor outcome.

A systematic review of the effects of dysphagia screening strategies on stroke patients found in-sufficient data supporting the effectiveness of im-plementing a dysphagia screening protocol, however, only three studies were included and because of the limited research available and no definite conclusions could be drawn 8 . Furthermore, there is no standard dysphagia screening protocol and no consensus has been reached regarding which protocols are best 21 ;. Considering this, it is meaningful that our study used a cost-effective, relatively simple method of clinical examination at the bedside and found that the im-plementation of this dysphagia screening protocol using a relatively simple method significantly reduced the incidence of pneumonia.

This study had several limitations. First, the sample size between the two groups was quite different which may affect statistical power. However, the Chi-square test, which is robust with respect to the size and distribution of the data, was used to compare the incidence of pneumonia between the two groups. Second, sensitivity, specificity, and accuracy analyses of our formal dysphagia screening program were not performed. However, we wanted to focus on evalu-ating outcomes after implementing a formal dysphagia screening program, and since there are still many stroke units worldwide that do not yet use formal screening protocol, we believe our study can support the existing stroke guideline recommendation. Third, the dysphagia screening was performed using clinical examinations and water swallowing test that are less sensitive than video fluoroscopic swallowing study and fiberoptic endoscopic examination of swallow-ing. Finally, due to the retrospective nature of this study, we could not verify pneumonia outcomes be-yond the information available in the medical re-cords.

The results of our study suggest that formal dys-phagia screening is associated with reduced risk of post-stroke aspiration pneumonia. Among the patients who underwent formal dysphagia screening, failing the dysphagia screening test, presentation with severe dysarthria, and conditions where dysarthria could not be evaluated were associated with increased risk of aspiration pneumonia. Our findings support the implementation of formal dysphagia screening for all stroke patients. Further large-scale prospective studies to confirm the effectiveness of the implementation of formal dysphagia screening for acute stroke patients to prevent aspiration pneumonia are necessary. 

This study was approved by the center’s institutional review board (S2017-1210-0003).

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Article

Original Article

J Korean Dysphagia Soc 2021; 11(1): 43-51

Published online January 30, 2021 https://doi.org/10.34160/jkds.2021.11.1.006

Copyright © The Korean Dysphagia Society.

Effectiveness of Formal Dysphagia Screening for Stroke Patients

Mi Ran Yoo, M.D.1, Yoon Mok Chun, M.D.1, Kyoung Hyo Choi, M.D.1, Sun Uck Kwon, M.D.2, Eun-Jae Lee, M.D.2

1Department of Rehabilitation Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, 2Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

Correspondence to:Kyoung Hyo Choi, Department of Rehabilitation Medicine, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea
Tel: +82-2-3010-3797, Fax: +82-2-3010-6964
E-mail: kyounghyochoi@gmail.com

Received: July 20, 2020; Revised: July 21, 2020; Accepted: August 28, 2020

Abstract

Objective: Early identification of dysphagia after stroke helps in preventing aspiration pneumonia. However, data are limited regarding the effectiveness of formal dysphagia screening for reducing the risk of aspiration pneumonia. The current study evaluates the effectiveness of formal dysphagia screening in stroke patients, to prevent future episodes of aspiration pneumonia.
Methods: The stroke registry of a tertiary hospital was retrospectively reviewed. We compared clinical variables and the incidence of aspiration pneumonia of patients hospitalized between 2014 and 2015 after formal screening was implemented, and patients hospitalized in 2011 when no established dysphagia screening protocol was in place. Additionally, we identified the incidence of pneumonia according to stroke severity, and evaluated the association with results obtained for incidence of pneumonia and dysphagia screening.
Results: A total of 2,902 patients were identified to have suffered acute stroke (2,018 who underwent formal dysphagia screening; 884 without screening). Patients with formal dysphagia screening developed pneumonia less frequently than patients not administered screening (1.3% with formal screening vs. 3.4% no formal screening, P<0.001). Pneumonia was significantly lower in patients with moderate and severe stroke who underwent formal dysphagia screening. Furthermore, failure of the dysphagia screening test, presentation with severe dysarthria, and conditions where dysarthria could not be evaluated, were independent predictors of pneumonia among patients who underwent formal screening.
Conclusion: Our findings demonstrate the association of formal dysphagia screening with reduced risk of post- stroke aspiration pneumonia, and indicates the efficacy of the procedure in identifying patients at higher risk of contracting pneumonia.

Keywords: Dysphagia, Screening, Stroke, Pneumonia, Aspiration

INTRODUCTION

Dysphagia after stroke is a common neurological symptom; 35-67% of acute stroke patients develop dysphagia1,2. Aspiration of food or oral secretions and dysfunction of the cough reflex in patients with dysphagia can lead to pneumonia. Stroke-associated pneumonia has been found to correlate with longer hospital stays, worse prognosis, and increased healthcare costs of stroke patients1 -5.

To prevent the above-mentioned problems caused by dysphagia in acute stroke patients, various met-hods can be utilized to identify dysphagia early. Met-hods for identifying dysphagia include dysphagia screening, which includes a swallowing test that can be conducted at the bedside or in–office, and more detailed dysphagia assessments, such as videofluoro-scopic swallowing study (VFSS) and fiberoptic endo-scopic examination of swallowing (FEES). Despite the effectiveness of these and other tests for identifying dysphagia, it is difficult to apply the above methods to all stroke patients due to limitations in manpower and cost, so dysphagia screening is often selectively applied to patients who are more likely to have dys-phagia3 -6.

Although it is not clear whether different methods of swallowing assessments reduce the risk of pneu-monia, disability, or death after stroke, the bedside screening test for dysphagia has been shown to effectively reduce pneumonia incidence rates when applied to patients with acute stroke6 -9.

Additionally, dysphagia screening before stroke patients begin oral intake has been recommended8. In several studies, implementation of dysphagia screening programs has been shown to reduce the incidence of pneumonia10,11. Moreover, the use of a formal dys-phagia screening protocol in a prospective 15-hospital study was reported to lead to a decrease in the in-cidence of pneumonia in stroke patients12.

Despite the recommendation of stroke manage-ment guideline8, the evidence level for recommen-dation is moderate grade, and insufficient evidence has been provided to establish that dysphagia screen-ing protocols effectively improve patient outcomes, such as by reducing pneumonia incidence8,13. In a recent study, no association between the use of dys-phagia screening and detailed dysphagia assessment and the risk of adverse outcomes including pneu-monia14.

We wanted to confirm whether the implementation of a formal dysphagia screening program where all acute stroke patients regardless of severity are screened can effectively reduce the incidence of pneumonia in stroke patients in our hospital. We also investigated the association between dysphagia screening result and incidence of pneumonia. The purpose of this study was to evaluate the effectiveness of formal dys-phagia screening in patients with stroke for the pre-vention of aspiration pneumonia.

MATERIALS AND METHODS

1. Study design

We retrospectively identified stroke patients who were hospitalized in the neurology department of a single tertiary hospital. All stroke (ischemic stroke, hemorrhagic stroke) diagnoses were confirmed by admitting neurologists. Patients who died during the hospitalization period were excluded.

Dysphagia screening was defined as the use of a simple non-invasive bedside swallow screening test. Until 2012, dysphagia screenings were performed by admitting neurologists without an established dys-phagia screening protocol. Also, the tests have been only applied for stroke patients with higher stroke severity.

A standardized dysphagia screening protocol was implemented in our institution in 2014. Since then, all stroke patients underwent documented dysphagia screening within 48 hours of hospital admission by a trained speech-language pathologist (SLP). The pa-tients were checked for mental status, dysarthria, facial palsy, and tongue impairment or dysphonia. And a dry swallow test was first performed and then a wet swallow test where the patient was instructed to drink a small volume of water was performed. The formal dysphagia screening tests have been routinely performed in all stroke patients regardless of stroke severity since 2014.

We compared screening results and outcomes of stroke patients who underwent formal dysphagia screening (classified as the ‘formal screening group’ of patients who were hospitalized between 2014 and 2015) and those who did not receive formal dysphagia screening (classified as the ‘no formal screening group’ of patients who were hospitalized in 2011).

Stroke patients who underwent formal dysphagia screening were further categorized into those who passed or failed the test so that outcomes could be compared. If the patient failed to swallow or swal-lowed with choking, wet hoarseness or changes in breathing in a dry swallow test or wet swallow test, each test was evaluated as failed test. If the patient failed either the dry swallow test or the wet swallow test, the patient was categorized into the group who failed the test.

This study was approved by the center’s insti-tutional review board (S2017-1210-0003).

2. Data and outcome variables

Demographic variables included age, sex, stroke type, stroke severity score by the National Institutes of Health Stroke Scale (NIHSS), stroke risk factors (heart disease, diabetes mellitus, hypertension, dys-lipidemia), level of consciousness (alert, not alert), presentation with dysarthria and modified Rankin Scale on admission.

Initial NIHSS scores were categorized into three groups: mild (NIHSS 0-4), moderate (NIHSS 5-15), severe (NIHSS 16-42).

The outcome of interest was the incidence of radiographically confirmed aspiration pneumonia within 30 days of hospitalization.

3. Diagnosis of aspiration pneumonia

Aspiration pneumonia was confirmed when all of the following conditions were met: (1) the patient developed new-onset fever; (2) at the time of fever occurrence, pneumonia or aspiration pneumonia was recorded as the cause of fever in the medical record, including the progress notes and/or consultation notes; (3) piperacillin/tazobactam was administered at the time of fever occurrence; (4) abnormal lab findings such as leukopenia, leukocytosis, or elevated C-reactive protein were identified; and (5) definitive abnormal findings on chest radiographs were identi-fied within 30 days of hospitalization 15,16 .

Patients were excluded if they: (1) were transferred from another hospital after receiving antibiotics, (2) had another potential fever origin such as urinary tract infection or thrombophlebitis, (3) or were diag-nosed with community-acquired pneumonia rather than hospital-acquired pneumonia.

4. Statistical analysis

Categorical variables are presented as percentages and continuous or discrete variables are presented as means±standard deviations. To compare the charac-teristics and the outcome of interest, the Student’s t-test was used for continuous variables and Fisher’s exact test and the chi-squared test were used for categorical variables.

The association between clinical variables and incidence of aspiration pneumonia was assessed by univariate logistic regression analysis. For clinical variables with P values<0.1 were included in multi-variable models. All potentially significant variables were included in multivariate logistic regression analysis. Multiple logistic regression analysis with stepwise fashioned variable selection was used to identify variables that were independent predictors of incidence of aspiration pneumonia.

The primary analysis was used to evaluate asso-ciations between the use of formal dysphagia screen-ing on the outcome of aspiration pneumonia. We also calculated the proportion of patients who failed the screening test. For the secondary analysis, we used multiple logistic regression to identify the effect of failing screening on the odds of patients developing pneumonia, with adjustment of potential confounders.

All statistical analyses were performed using SPSS version 18.0 (IBM Inc., Armonk, NY, USA). Differ-ences were considered to be statistically significant when P<0.05.

RESULTS

Between January 1st, 2011, and December 31st, 2011, 901 patients who were admitted to the neuro-logy department for stroke without undergoing for-mal dysphagia screening were identified; the medical charts of 12 patients were irretrievable and 5 patients were excluded (1 was admitted for another reason and 4 died during the hospitalization period), leaving 884 patients to be included in the no formal screen-ing group. Between January 1st, 2014, and December 31st, 2015, 2,054 stroke patients were admitted and underwent formal dysphagia screening; the medical charts of 27 patients were irretrievable and 9 patients were excluded because they were admitted for an-other reason, leaving 2,018 patients in the formal screening group.(Fig. 1)

Figure 1. Flow diagram of patients did or did not undergo formal dysphagia screening.

Table 1 shows the comparison of clinical variables between patients who did or did not undergo formal dysphagia screening. There were no significant dif-ference in the distribution of sex, age, hypertension, diabetes mellitus status, cardiac disease, dyslipidemia, level of consciousness, presentation with dysarthria, mean NIHSS stroke severity score, and modified Rankin Scale at admission between the two groups. There was also no significant difference in the dis-tribution of NIHSS scores between the groups of patients who either did or did not undergo formal dysphagia screening. There were significantly more ischemic stroke patients in the formal dysphagia screening group than the no formal screening group (ischemic stroke with no formal screening, 90.4% (799/884) vs. formal screening, 93.6% (1,889/2,018); P=0.004). Meanwhile, when comparing the two groups, the proprotions of patients receiving non-oral diet was similar in both groups, but the proportion of patients receiving a modified diet was higher in the formal dysphagia screening group (non-oral diet with no formal screening, 17.6% (156/884) vs. formal screening, 16.2% (326/2018), modified diet with no formal screening, 28.9% (255/884) vs. formal screening, 38.5% (777/2,018); P=0.01).

Table 1 . Patient characteristics and incidence of pneumonia of patients who did or did not undergo formal dysphagia screening.

VariableNo formal screening group (n=884)Formal screening group (n=2018)P value
Sex
Female/Male340/544770/12480.88
Age64.7±12.965.2±13.60.24
Stroke type0.004*
Ischemic799 (90.4%)1889 (93.6%)
Hemorrhagic85 (9.6%)129 (6.4%)
Pneumonia30 (3.4%)26 (1.3%)<0.001*
Hypertension567 (64.1%)1246 (61.8%)0.23
Diabetes mellitus255 (28.8%)577 (28.6%)0.89
Cardiac disease273 (30.9%)588 (28.2%)0.35
Dyslipidemia221 (25.0%)497 (24.7%)0.84
Mental status0.74
Alert817 (92.4%)1872 (92.8%)
Non alert67 (7.6%)146 (7.2%)
Dysarthria0.73
None or mild607 (68.7%)1404 (69.6%)
Severe197 (22.3%)449 (22.2%)
Undeterminable80 (9.0%)165 (8.2%)
Mean NIHSS score5.08±5.45.24±5.10.20
NIHSS group0.66
Mild520 (58.8%)1159 (57.4%)
Moderate304 (34.4%)730 (36.1%)
Severe60 (6.8%)130 (6.4%)
mRS at admission0.51
0-2472 (53.4%)1104 (54.7%)
3-5412 (46.6%)914 (45.3%)
Diet recommendation0.01*
Non-oral156 (17.6%)326 (16.2%)
Modified diet255 (28.9%)777 (38.5%)
Regular diet473 (53.5%)915 (45.3%)

**P<0.05, statistically significant by Chi-squared test.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale.



The proportion of patients diagnosed with aspiration pneumonia was significantly lower in the formal dysphagia screening group than in the no formal screening group (1.3% (26/2,018) vs. 3.4% (30/884); P< 0.001).

The subgroup analysis of patients diagnosed with aspiration pneumonia according to NIHSS group is shown in Table 2. The proportion of patients diag-nosed with aspiration pneumonia was significantly lower in the formal dysphagia screening group when compared to the no formal screening group among moderate and severe stroke patients (moderate, no formal screening 5.4% vs. formal screening 1.5%, P=0.005; severe, no formal screening 4.2% vs. formal screening 2.6%; P=0.02); there was no significant difference in the proportions of mild stroke patients diagnosed with aspiration pneumonia between the two groups (no formal screening 0.3% vs. formal screening 0.2%; P=0.11).

Table 2 . Subgroup analysis of aspiration pneumonia incidence according to NIHSS group.

NIHSS groupNo formal screening group (n=884)Formal screening group (n=2018)P value
Mild (n=1679)5 (0.3%)10 (0.2%)0.11
Moderate (n=1033)17 (5.4%)16 (1.5%)0.005*
Severe (n=190)8 (4.2%)3 (2.6%)0.02**

*P<0.05, statistically significant by Chi-squared test, **P<0.05, statistically significant by Fisher’s exact test.

CXR: Chest X-ray, NIHSS: National Institutes of Health Stroke Scale.



Table 3 shows the univariate and multivariate logi-stic regression analyses of clinical variables associ-ated with aspiration pneumonia incidence. In the univariate logistic regression analysis, increasing age, level of consciousness (not alert), increasing stroke severity indicated by NIHSS score, modified Rankin Scale (mRS) at admission (3-5), presentation with dys-arthria (severe or undeterminable) and not receiving formal dysphagia screening were significantly associ-ated with the development of aspiration pneumonia. Not receiving formal dysphagia screening, lower level of function according to mRS scores, severe dys-arthria, and conditions where dysarthria cannot be evaluated were independent predictors of pneumonia in the multivariate regression analysis. The adjusted odds ratio of developing pneumonia in patients who underwent dysphagia screening was 0.36 (95% CI, 0.20 to 0.62).

Table 3 . Univariate and multivariate logistic regression analyses of clinical variables for association with aspiration pneumonia incidence.

Univariate analysisMultivariate analysis


OR95% CIP valueOR95% CIP value
Formal dysphagia screening0.370.22-0.63<0.000*0.360.20-0.62<0.000*
Age1.041.01-1.06<0.002*1.031.01-1.060.51
Sex (Male)0.890.51-1.540.67
Stroke type
IschemicReference-----
Hemorrhagic2.431.17-5.020.101.990.93-4.270.08
Mental status
AlertReference
Not alert5.523.03-10.1<0.000*1.180.58-2.410.65
Stroke severity (NIHSS)1.161.12-1.20<0.000*1.120.95-1.090.64
mRS at admission
0-2Reference-----
3-58.413.80-18.70<0.000*2.771.12-6.830.027*
Dysarthria
None or mildReference-----
Severe5.672.86-11.3<0.000*2.401.09-5.290.030*
Undeterminable12.96.30-26.5<0.000*2.850.99-8.190.049*

*P<0.05, statistically significant.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale, OR: odds ratio, CI: confidence interval.



Table 4 shows the baseline characteristics of pa-tients who either passed or failed the formal dyspha-gia screening test. Of the 2,018 patients who under-went formal dysphagia screening, 330 (16.4%) patients failed. Patients who failed screening had lower levels of consciousness, higher stroke severity, more fre-quent severe dysarthria, lower levels of function according to mRS scores, and were more often placed on a non-oral diet regime. The proportion of patients diagnosed with aspiration pneumonia was signifi-cantly higher in the patients who failed the dysphagia screening test than in the patients who passed the screening test (5.5% (4/330) vs. 0.4% (21/1688); P< 0.001).

Table 4 . Characteristics of patients who passed or failed the formal dysphagia screening test.

VariableDysphagia screening resultP value

PassFail
N (%)1,688 (83.6%)330 (16.4%)
Sex
Female/Male644/1,044126/2040.11
Age64.9±13.567.8±13.50.73
Stroke type0.23
Ischemic1,580 (93.9%)309 (92.1%)
Hemorrhagic108 (6.1%)21 (7.9%)
Pneumonia21 (0.4%)4 (5.5%)<0.001***
Hypertension1,042 (61.8%)204 (61.5%)0.92
Diabetes mellitus483 (29.2%)94 (25.5%)0.17
Cardiac disease492 (27.9%)96 (29.5%)0.60
Dyslipidemia416 (25.0%)81 (22.7%)0.38
Mental status
Not alert29 (1.7%)117 (35.5%)<0.001*
Mean NIHSS score3.75±3.3912.86±5.81<0.001**
NIHSS group<0.001*
Mild1,127 (66.8%)32 (9.7%)
Moderate546 (32.3%)183 (55.5%)
Severe15 (0.9%)115 (34.8%)
Dysarthria<0.001*
Severe314 (18.6%)135 (40.9%)
Undeterminable29 (1.7%)136 (41.2%)
mRS at admission<0.001*
3-5615 (36.4%)299 (90.6%)
Diet recommendation<0.001*
Non-oral2 (0.1%)326 (98.8%)
Modified diet773 (45.8%)4 (1.2%)

*P<0.05, statistically significant by Chi-squared test, ** P<0.05, statistically significant by Independent t-test, ***P<0.05, statis-tically significant by Fisher’s exact test.

NIHSS: National Institutes of Health Stroke Scale.



The univariate and multivariate logistic regression analyses for incidence of aspiration pneumonia of patients who underwent formal dysphagia screening are shown in Table 5. In the multivariate analysis, compared to those who passed screening, patients who failed screening had a significantly higher risk of pneumonia (5.5% vs. 0.4%; aOR, 5.53; 95% CI, 1.87- 16.4). Meanwhile, presentation with severe dysarthria and conditions where dysarthria could not be evalu-ated were found to be independent predictors of pneumonia in the multivariate regression analysis (22.2%; aOR, 4.48; 95% CI, 1.25-16.04; 8.2%; aOR, 1.50; 95% CI, 1.49-26.70, respectively).

Table 5 . Univariate and multivariate logistic regression analyses for incidence of aspiration pneumonia of patients who underwent routine dysphagia screening.

Univariate analysisMultivariate analysis


OR95% CIP valueOR95% CIP value
Sex (Male)0.890.51-1.540.67
Mental status
AlertReference-----
Not alert6.332.68-14.92<0.000*1.450.54-3.950.46
Stroke severity (NIHSS)1.161.12-1.20<0.000*0.970.88-1.080.61
mRS at admission
0-2Reference-----
3-58.413.80-18.70<0.000*1.250.30-5.270.76
Dysarthria
None or mildReference-----
Severe8.792.86-27.3<0.000*4.481.25-16.040.021*
Undeterminable12.906.30-36.5<0.000*1.501.49-26.700.012*
Results of dysphagia screen
PassReference-----
Fail13.855.74-33.450.000*5.531.87-16.40.002*

*P<0.05, statistically significant.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale, OR: odds ratio, CI: confidence interval.


DISCUSSION

We found that formal dysphagia screening is asso-ciated with lower risk of pneumonia in acute stroke patients when compared to acute stroke patients who did not undergo formal screening. Furthermore, among patients who underwent formal dysphagia screening, failing a dysphagia screening test, pre-sentation with severe dysarthria, and conditions where dysarthria cannot be evaluated were independent predictors of aspiration pneumonia.

Although many efforts have been made to imple-ment early screening for dysphagia in stroke patients, the adherence rates for dysphagia screening pro-tocols remains low, and some acute stroke units still have no formal screening protocol 12 . Meanwhile, there is insufficient evidence that the formal dys-phagia screening protocol effectively improves pa-tient outcomes.

Since 2014, our institution has followed a formal dysphagia screening protocol and it was performed in stroke patients of all severity levels including mild stroke at the time of admission to the neurology department. Before 2012, dysphagia screening was only used for patients with higher stroke severity levels. Notably, our study identified significantly fewer aspiration pneumonia cases among patients after formal dysphagia screening was implemented. We found that implementing the formal dysphagia screening reduced the incidence of aspiration pneumonia, even after adjusting for stroke severity.

These findings are similar to those of a previous study that also found that implementation of a formal dysphagia screening protocol was associated with reduced risk of pneumonia 12 . Other institutions have also implemented dysphagia screening programs with similar results. For example, Yeh et al. reported that dysphagia screening was associated with a decrease in stroke-associated pneumonia in all stroke patients after adjusting for factors such as stroke severity 17 . Judith et al. also found that the pneumonia rate was lower in patients who were screened with the formal dysphagia screening process and even after adjusting for stroke severity, and formal dysphagia screening was associated with fewer patients developing pneu-monia 12 .

Although patients with mild stroke are not com-pletely without risk for hospital-acquired pneumonia, they are often not considered for dysphagia screening because of their low risk of developing pneumonia. Joundi et al. reported that mild stroke patients were half as likely to be screened as moderate stroke pa-tients. However, patients with mild severity of stroke had moderate rates of dysphagia screening failure and substantial risk of complications after failing the screening test 18 .

The subgroup analysis according to stroke severity score found that aspiration pneumonia was less com-mon among patients with moderate and severe stroke severity after the formal dysphagia screening pro-gram was implemented. Although the difference was not significant, aspiration pneumonia was also some-what lower among mild stroke patients who under-went formal dysphagia screening when compared to patients who did not undergo formal screening.

Several studies have reported that failing the dys-phagia screening test is a powerful predictor of poor outcomes such as pneumonia 14,18 , more severe dis-ability 14,18 , and higher likelihood of the patient being discharged to a long-term care facility, even in pa-tients with mild strokes, who are less likely to be screened 18 . The current study also showed that failing the dysphagia screening test is a strong predictor of aspiration pneumonia occurrence, with an adjusted odds ratio of 5.53. Similar odds ratios have been re-ported in other studies as 4.71 18 and 3.00 14 . Further-more, not only failing a dysphagia screening test, presentation with severe dysarthria and conditions where dysarthria cannot be evaluated were also sig-nificant factor which were associated with the inci-dence of aspiration pneumonia of stroke patients who had underwent the formal dysphagia screening program. These findings were consistent with sug-gestions from several other studies 19,20 . Therefore, we suggest that formal dysphagia screening can be ef-fective to identify patients at higher risk such as failing the screening or presence of dysarthria for developing poor outcome.

A systematic review of the effects of dysphagia screening strategies on stroke patients found in-sufficient data supporting the effectiveness of im-plementing a dysphagia screening protocol, however, only three studies were included and because of the limited research available and no definite conclusions could be drawn 8 . Furthermore, there is no standard dysphagia screening protocol and no consensus has been reached regarding which protocols are best 21 ;. Considering this, it is meaningful that our study used a cost-effective, relatively simple method of clinical examination at the bedside and found that the im-plementation of this dysphagia screening protocol using a relatively simple method significantly reduced the incidence of pneumonia.

This study had several limitations. First, the sample size between the two groups was quite different which may affect statistical power. However, the Chi-square test, which is robust with respect to the size and distribution of the data, was used to compare the incidence of pneumonia between the two groups. Second, sensitivity, specificity, and accuracy analyses of our formal dysphagia screening program were not performed. However, we wanted to focus on evalu-ating outcomes after implementing a formal dysphagia screening program, and since there are still many stroke units worldwide that do not yet use formal screening protocol, we believe our study can support the existing stroke guideline recommendation. Third, the dysphagia screening was performed using clinical examinations and water swallowing test that are less sensitive than video fluoroscopic swallowing study and fiberoptic endoscopic examination of swallow-ing. Finally, due to the retrospective nature of this study, we could not verify pneumonia outcomes be-yond the information available in the medical re-cords.

CONCLUSION

The results of our study suggest that formal dys-phagia screening is associated with reduced risk of post-stroke aspiration pneumonia. Among the patients who underwent formal dysphagia screening, failing the dysphagia screening test, presentation with severe dysarthria, and conditions where dysarthria could not be evaluated were associated with increased risk of aspiration pneumonia. Our findings support the implementation of formal dysphagia screening for all stroke patients. Further large-scale prospective studies to confirm the effectiveness of the implementation of formal dysphagia screening for acute stroke patients to prevent aspiration pneumonia are necessary. 

ACKNOWLEDGEMENTS

None.

CONFLICT OF INTEREST

The authors declare that they have no conflict of interest.

ETHICS

This study was approved by the center’s institutional review board (S2017-1210-0003).

FUNDING

None.

Fig 1.

Figure 1.Flow diagram of patients did or did not undergo formal dysphagia screening.
Journal of the Korean Dysphagia Society 2021; 11: 43-51https://doi.org/10.34160/jkds.2021.11.1.006

Table 1 . Patient characteristics and incidence of pneumonia of patients who did or did not undergo formal dysphagia screening.

VariableNo formal screening group (n=884)Formal screening group (n=2018)P value
Sex
Female/Male340/544770/12480.88
Age64.7±12.965.2±13.60.24
Stroke type0.004*
Ischemic799 (90.4%)1889 (93.6%)
Hemorrhagic85 (9.6%)129 (6.4%)
Pneumonia30 (3.4%)26 (1.3%)<0.001*
Hypertension567 (64.1%)1246 (61.8%)0.23
Diabetes mellitus255 (28.8%)577 (28.6%)0.89
Cardiac disease273 (30.9%)588 (28.2%)0.35
Dyslipidemia221 (25.0%)497 (24.7%)0.84
Mental status0.74
Alert817 (92.4%)1872 (92.8%)
Non alert67 (7.6%)146 (7.2%)
Dysarthria0.73
None or mild607 (68.7%)1404 (69.6%)
Severe197 (22.3%)449 (22.2%)
Undeterminable80 (9.0%)165 (8.2%)
Mean NIHSS score5.08±5.45.24±5.10.20
NIHSS group0.66
Mild520 (58.8%)1159 (57.4%)
Moderate304 (34.4%)730 (36.1%)
Severe60 (6.8%)130 (6.4%)
mRS at admission0.51
0-2472 (53.4%)1104 (54.7%)
3-5412 (46.6%)914 (45.3%)
Diet recommendation0.01*
Non-oral156 (17.6%)326 (16.2%)
Modified diet255 (28.9%)777 (38.5%)
Regular diet473 (53.5%)915 (45.3%)

**P<0.05, statistically significant by Chi-squared test.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale.


Table 2 . Subgroup analysis of aspiration pneumonia incidence according to NIHSS group.

NIHSS groupNo formal screening group (n=884)Formal screening group (n=2018)P value
Mild (n=1679)5 (0.3%)10 (0.2%)0.11
Moderate (n=1033)17 (5.4%)16 (1.5%)0.005*
Severe (n=190)8 (4.2%)3 (2.6%)0.02**

*P<0.05, statistically significant by Chi-squared test, **P<0.05, statistically significant by Fisher’s exact test.

CXR: Chest X-ray, NIHSS: National Institutes of Health Stroke Scale.


Table 3 . Univariate and multivariate logistic regression analyses of clinical variables for association with aspiration pneumonia incidence.

Univariate analysisMultivariate analysis


OR95% CIP valueOR95% CIP value
Formal dysphagia screening0.370.22-0.63<0.000*0.360.20-0.62<0.000*
Age1.041.01-1.06<0.002*1.031.01-1.060.51
Sex (Male)0.890.51-1.540.67
Stroke type
IschemicReference-----
Hemorrhagic2.431.17-5.020.101.990.93-4.270.08
Mental status
AlertReference
Not alert5.523.03-10.1<0.000*1.180.58-2.410.65
Stroke severity (NIHSS)1.161.12-1.20<0.000*1.120.95-1.090.64
mRS at admission
0-2Reference-----
3-58.413.80-18.70<0.000*2.771.12-6.830.027*
Dysarthria
None or mildReference-----
Severe5.672.86-11.3<0.000*2.401.09-5.290.030*
Undeterminable12.96.30-26.5<0.000*2.850.99-8.190.049*

*P<0.05, statistically significant.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale, OR: odds ratio, CI: confidence interval.


Table 4 . Characteristics of patients who passed or failed the formal dysphagia screening test.

VariableDysphagia screening resultP value

PassFail
N (%)1,688 (83.6%)330 (16.4%)
Sex
Female/Male644/1,044126/2040.11
Age64.9±13.567.8±13.50.73
Stroke type0.23
Ischemic1,580 (93.9%)309 (92.1%)
Hemorrhagic108 (6.1%)21 (7.9%)
Pneumonia21 (0.4%)4 (5.5%)<0.001***
Hypertension1,042 (61.8%)204 (61.5%)0.92
Diabetes mellitus483 (29.2%)94 (25.5%)0.17
Cardiac disease492 (27.9%)96 (29.5%)0.60
Dyslipidemia416 (25.0%)81 (22.7%)0.38
Mental status
Not alert29 (1.7%)117 (35.5%)<0.001*
Mean NIHSS score3.75±3.3912.86±5.81<0.001**
NIHSS group<0.001*
Mild1,127 (66.8%)32 (9.7%)
Moderate546 (32.3%)183 (55.5%)
Severe15 (0.9%)115 (34.8%)
Dysarthria<0.001*
Severe314 (18.6%)135 (40.9%)
Undeterminable29 (1.7%)136 (41.2%)
mRS at admission<0.001*
3-5615 (36.4%)299 (90.6%)
Diet recommendation<0.001*
Non-oral2 (0.1%)326 (98.8%)
Modified diet773 (45.8%)4 (1.2%)

*P<0.05, statistically significant by Chi-squared test, ** P<0.05, statistically significant by Independent t-test, ***P<0.05, statis-tically significant by Fisher’s exact test.

NIHSS: National Institutes of Health Stroke Scale.


Table 5 . Univariate and multivariate logistic regression analyses for incidence of aspiration pneumonia of patients who underwent routine dysphagia screening.

Univariate analysisMultivariate analysis


OR95% CIP valueOR95% CIP value
Sex (Male)0.890.51-1.540.67
Mental status
AlertReference-----
Not alert6.332.68-14.92<0.000*1.450.54-3.950.46
Stroke severity (NIHSS)1.161.12-1.20<0.000*0.970.88-1.080.61
mRS at admission
0-2Reference-----
3-58.413.80-18.70<0.000*1.250.30-5.270.76
Dysarthria
None or mildReference-----
Severe8.792.86-27.3<0.000*4.481.25-16.040.021*
Undeterminable12.906.30-36.5<0.000*1.501.49-26.700.012*
Results of dysphagia screen
PassReference-----
Fail13.855.74-33.450.000*5.531.87-16.40.002*

*P<0.05, statistically significant.

NIHSS: National Institutes of Health Stroke Scale, mRS: modified Rankin Scale, OR: odds ratio, CI: confidence interval.


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