Reclassification of items in the Leicester Cough Questionnaire: Correlation analysis

Background: The Leicester Cough Questionnaire (LCQ) is a validated tool for assessing cough that has three domains (physical, psychological, and social), with eight, seven, and four items, respectively. However, the assigned domain may not accurately reflect the characteristics of an item. This study aimed to reclassify the items in the Korean version of the LCQ (K-LCQ) to improve the coherence in each domain. Methods: Data of patients with chronic cough from 16 centers who completed the K-LCQ were retrospectively analyzed. Spearman's rank correlation analysis was used to assess the correlations between items and their domains. Principal component analysis was performed to recategorize the K-LCQ items. Results: The correlation analysis of the data from 255 patients demonstrated that certain items such as tiredness, embarrassment, and interference with daily work or overall life enjoyment showed strong or very strong correlations with all three domains. Cough bout frequency showed the weakest correlation with the physical domain, despite being included in that domain, and had stronger correlations with the psychological and social domain. The principal component analysis led to the reclassification of six items: one from the physical to psychological, two from the social to psychological, and three from the psychological to social domain. The within-domain correlation coherence was higher in the new classification than in the original. Validation using an independent cohort of 203 patients yielded similar results. Conclusions: The new classification of the K-LCQ items showed improved within-domain correlation coherence.