A systematic review of the psychometric properties of the Leicester Cough Questionnaires based on the COSMIN guidelines

Background: Chronic cough affects around 10 % of the general adult population, impairing all aspects of quality of life. Research question: What are the Leicester Cough Questionnaire's psychometric properties? Study design and methods: Electronic searches of PubMed, CINAHL, and ScienceDirect databases were conducted from inception until October 1rst 2022. All full-text articles, published in French or English, aimed at evaluating the LCQ's content validity or psychometric properties were included. The COSMIN Risk of Bias checklist was applied to assess their methodological quality and results. Results were qualitatively summarised and rated by a modified GRADE approach. Results: 40 studies were included accounting for 8731 adults, subject to cough or a respiratory condition. Chronic cough (>8 weeks) was the most represented. The LCQ's total score is relevant and comprehensible for the assessment of the impact of cough on QoL. The original 3-factor model showed a satisfactory model fit. Good convergent validity was found for the total and physical domain scores. These scores demonstrate good internal consistency and test retest reliability, with some variability noted and they are responsive to change. Recent estimates of MID thresholds were 1.7 and 0.4 for total and domain scores respectively. The quality of the studies is globally poor. Interpretation: The LCQ is a valid outcome to assess the intra-individual impact of cough on QoL and to detect large changes in quality of life mainly in a short-term clinical trial setting. Clinical trial registration: The protocol was registered with PROSPERO (CRD42022355191).