Validation of the reliability and clinical value of the simplified cough score

Abstract

Objective To validate the repeatability of the simplified cough score and its responsiveness to effective treatment and investigate the relationship between the simplified cough score and cough symptom score.Methods A total of 119 patients with chronic cough referred to our respiratory clinic were recruited into the study between June 2010 and February 2011. Cough severity was evaluated by the simplified cough score,cough symptom score,Leicester cough questionnaire,and cough reflex sensitivity detection,and the correlations among them were analyzed.The change ratio,effect size,and standardized response mean of the simplified cough score were calculated after a 2-week course of effective treatment.The repeatability of the simplified cough score was assessed in 99 untreated patients with stable chronic cough.Results The intraclass correlation coefficient in a 3-day test-retest interval of simplified cough score was 0.90 ( 95 ％ CI =0.84 - 0.92,P =0.00 ) for daytime and 0.89 ( 95 ％ CI =0.91 - 0.96,P =0.00 ) for nighttime. There was an obvious positive linear correlation between the simplified cough score and cough symptom score ( daytime:r =0.82,P =0.00 ; nighttime:r =0.92,P =0.00 ),a significant negative linear correlation between the cough score and Leicester cough questionnaire,and a weak but significant negative correlation between the simplified cough score and cough threshold C2 or C5 to capsaicin. After a 2-week course of effective treatment,the change ratio,effect size,and standardized response mean were 46.71％,1.16,and 1.05 for daytime and 71.87％,1.09,and 1.10 for nighttime,respectively.Conclusion The simplified cough score is a reliable and valid tool for evaluation of cough severity in clinical practice. Key words: Cough; Simplified cough score; Cough symptom score