Comparison of cough reflex test against instrumental assessment of aspiration

Abstract

Background: Silent aspiration is associated with pneumonia and mortality, and is poorly identified by traditional clinical swallowing evaluation (CSE). The aim of this study was to validate cough reflex testing (CRT) for identification of silent aspiration against aspiration confirmed by instrumental assessment.

Methods: Cough reflex threshold testing was completed on all patients using inhaled, nebulised citric acid. Within an hour, 80 patients underwent videofluoroscopic study of swallowing (VFSS) and 101 patients underwent fibreoptic endoscopic evaluation of swallowing (FEES). All tests were recorded and analysed by two researchers blinded to the result of the alternate test.

Results: Significant associations between CRT result and cough response to aspiration on VFSS (X(2) (2)=11.046, p=.003) and FEES (X(2) (2)=34.079, p<.001) were identified. Sensitivity and specificity were optimised at 0.6mol/L in patients undergoing VFSS (71%, 60% respectively) and at 0.4mol/L in patients undergoing FEES (69%, 71% respectively). A concentration of 0.8mol/L had the highest odds ratio (OR) for detecting silent aspiration (8 based on VFSS; 7 based on FEES).

Conclusion: CRT results are significantly associated with aspiration response on instrumental assessment. Lower concentrations of citric acid provide a better predictive measure of silent aspiration.

Keywords: CI; CRT; CSE; Cough reflex testing; Dysphagia; FEES; LR+; LR−; NPV; OR; PPV; Silent aspiration; VFSS; Validity; clinical swallowing evaluation; confidence interval; cough reflex testing; fibreoptic endoscopic evaluation of swallowing; negative likelihood ratio; negative predictive value; odds ratio; positive likelihood ratio; positive predictive value; videofluoroscopic study of swallowing.