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Three Part Question

In [adults with acquired dysphagia], is failed [cough reflex test] a sensitive and specific predictor of [silent aspiration]?

Clinical Scenario

An 86 year old man is admitted to the respiratory ward with his third pneumonia in 6 months. A bedside swallow exam is abnormal however; no overt signs of aspiration / penetration are evident. The next available date for videofluoroscopy is in a week. We wonder if there is a sensitive predictor of silent aspiration that could be used at bedside. We have heard of cough reflex testing but wonder about its evidence base.

Search Strategy

[dysphagia OR swallow* difficult*] AND [cough* reflex test* OR cough* response* OR citric acid cough*] AND [silent aspirat*]
Databases searched: CINAHL; EMBASE; Medline; AMED; PsychINFO

Search Outcome

29 papers found; plus additional one added via hand searching reference lists.
22 excluded as not relevant to three part question as a reference standard test was not used.
7 were included for appraisal.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Wakasugi, Y. et al 2008 Japan	204 adult inpatients and outpatients with suspected dysphagia of varying aetiologies.	2B - validating cohort study	Sensitivity and specificity of cough reflex test in silent aspirators with trace aspirators included	Sensitivity was 0.67 and specificity was 0.90	No sample size calculations specified. Researcher not blinded to reference standard test result (videofluoroscopy / nasendoscopy) and cough reflex test result.
			Sensitivity and specificity of cough reflex test in silent aspirators with trace aspirators excluded	Sensitivity was 0.87 and specificity was 0.89.
Sato, M. et al 2012 Japan	141 consecutive adults who complained of dysphagic symptoms with varying aetiologies.	2B - validating cohort study	Sensitivity and specificity of cough reflex test in all participants (aspirators and non-aspirators)	Sensitivity was 0.81 and specificity was 0.65.	Query effect of nasal anesthesia used during FEES procedure (reference standard) on incidence of aspiration / penetration. No sample size calculations specified.
			Sensitivity and specificity of cough reflex test in participants who aspirated	Sensitivity was 0.92 and specificity was 0.94.
Miles, A. et al 2013 New Zealand	181 consecutive adults referred for videofluoroscopy or FEES over two sites, with varying aetiology.	2B - Validating cohort study	Sensitivity and specificity of cough reflex test for patients who aspirated on videofluoroscopy	Sensitivity was 0.71 and specificity was 0.71	Split over two sites, with different reference standard tests. Evidence that the results from the two sites differed significantly.
			Sensitivity and specificity of cough reflex test for patients who aspirated on FEES	Sensitivity was 0.69 and specificity was 0.71
			Sensitivity and specificity of cough reflex test with trace aspirators (on FEES) removed from analyses	Sensitivity was 0.85 and specificity was 0.71
			Sensitivity and specificity of cough reflex test on full videofluoroscopy cohort, both aspirators and non-aspirators	Sensitivity was 0.71 and specificity was 0.6
			Sensitivity and specificity of cough reflex test on full FEES cohort, both aspirators and non-aspirators	Sensitivity was 0.69 and specificity was 0.71
			Sensitivity of cough reflex test on full FEES cohort, when trace aspirators are included in the non-aspirator group for analyses	Sensitivity was 0.75
			Sensitivity and specificity of cough reflex test (CRT) on aspirators on videofluoroscopy, when weak cough on CRT analysed as fail instead of pass	Sensitivity was 0.94 and specificity was 0.71
			Sensitivity and specificity of cough reflex test (CRT) on aspirators on FEES, when weak cough on CRT analysed as fail instead of pass	Sensitivity was 0.83 and specificity was 0.59
			Sensitivity and specificity of cough reflex test (CRT) on full videofluoroscopy cohort, when weak cough on CRT analysed as fail instead of pass	Sensitivity was 0.94 and specificity was 0.24
			Sensitivity and specificity of cough reflex test (CRT) on full FEES cohort, when weak cough on CRT analysed as fail instead of pass	Sensitivity was 0.83 and specificity was 0.55
Lee, J. et al 2014 Korea	101 females with dysphagia of central nervous system aetiology and 59 healthy female controls.	2B - validating cohort study	Sensitivity and specificity of cough reflex test in detecting aspiration in all dysphagic patients	Sensitivity was 0.74 and specificity was 0.73	Only females. Researches not blinded to result of reference standard or cough reflex test. No sample size calculations specified.
			Sensitivity and specificity of cough reflex test in detecting silent aspiration in all dysphagic patients	Sensitivity was 0.87 and specificity was 0.70
Wakasugi, Y. et al 2014 Japan	160 patients with suspected dysphagia who underwent videofluoroscopy or FEES	2B - validating cohort study	Sensitivity and specificity of cough reflex test in full cohort	Sensitivity was 0.86 and specificity was 0.71	Researchers were not blinded to results of reference standard or cough reflex tests. Patients who aspirated large amounts and coughed, but did not cough on trace aspiration were not considered silent aspirators. No sample size calculations specified. recruitment methods unclear. Inclusion and exclusion criteria not defined. Unclear methodology making it difficult to reproduce.
			Sensitivity and specificity of cough reflex test in patients who aspirated	Sensitivity was 0.86 and specificity was 0.69
Guillen-Sola, A. et al 2015 Spain	258 consecutive stroke patients admitted to inpatient rehabilitation; 124 excluded (n= 134)	1B - validating cohort study	Sensitivity and specificity of cough reflex test for full cohort	Sensitivity was 0.19 and specificity was 0.71	Exclusion criteria were extensive and potentially inappropriate. For example, patients deemed to be at 'low risk' of silent aspiration on bedside exam were excluded. Sample size calculations not specified. Poor external validity as only included stroke patients suitable for extensive rehabilitation.
Kallesen, M. et al 2016 New Zealand	106 recently extubated patients on critical care who had required invasive ventilation	1B - validating cohort study	Sensitivity and specificity of cough reflex test in detecting silent aspiration in full cohort where weak cough response was grouped with absent cough response	Sensitivity was 0.88 and specificity was 0.58
			Sensitivity and specificity of cough reflex test in full cohort where weak cough response was grouped with strong cough response	Sensitivity was 0.63 and specificity was 0.66
			Sensitivity and specificity of cough reflex test in detecting aspiration in full cohort where weak cough response was grouped with absent cough response	Sensitivity was 0.85 and specificity was 0.50

Comment(s)

There is emerging evidence that cough reflex testing, as a stand alone assessment, is of limited benefit in identifying silent aspirators in a group of dysphagic patients. It is better able to identify silent aspirators who aspirate larger amounts in a group of aspirating patients. This is of little clinical benefit. It is particularly poor at identifying trace silent aspirators. One study suggests that combining cough reflex testing with bedside swallowing assessment may improve clinical usefulness of cough reflex testing. More research is required.

Clinical Bottom Line

Cough reflex testing is not specific or sensitive enough to identify silent aspiration in adult dysphagic patients.

References

1. Wakasugi, Y., Tohara, H., Hattori, F., Motohashi, Y., Nakane, A., Goto, S., Ouchi, Y., Mikushi, S., Takeuchi, S. & Uematsu, H. Screening test for silent aspiration at the bedside. Dysphagia 2008; 23: 364 - 370
2. Sato, M., Tohara, H., iida, T., Wada, S., Inoue, M. & Ueda, K. Simplified Cough Test for Screening Silent Aspiration Archives of Physical Medicine and Rehabilitation 2012; 93: 1982 - 1986
3. Miles, A., Moore, S., McFarlane, M., Lee, F., Allen, J. & Huckabee, M. Comparison of cough reflex test against instrumental assessment of aspiration Physiology & Behavior 2013; 118: 25 - 31
4. Lee, J., Kim, D., Seo, K. & Kang, S. Usefulness of the simplified cough test in evaluating cough reflex sensitivity as a screening test for silent aspiration Annals of Rehabilitation Medicine 2014; 38 (4): 476 - 484
5. Wakasugi, Y., Tohara, H., Nakane, A., Murata, S., Mikushi, S., Susa, C., Takashima, M., Umeda, Y., Suzuki, R. & Uematsu, H. Usefulness of a handheld nebulizer in cough test to screen for silent aspiration. Odontology 2014; 102: 76 - 80
6. Guillen-Sola, A., Chiarella, S., Martinez-Orfila, J., Duarte, E., Alvarado-Panesso, M., Figueres-Cugat, A., Bas, N. & Marco, E. Usefulness of citirc acid cough test for screening of silent aspiration in subacute stroke patients: a prospective study Archives of Physical Medicine and Rehabilitation 2015; 96(7): 1277 - 1283
7. Kallesen, M., Psirides, A. & Huckabee, M. Comparison of cough reflex testing with videoendoscopy in recently extubated intensive care unit patients. Journal of Critical Care 2016; 33: 90 - 94