Patient-reported outcome measures for cough used in interstitial lung disease: a systematic review.

Introduction: Validated and reliable patient-reported outcome measures (PROMs) are recommended to assess the severity and impact of cough in interstitial lung disease (ILD). We systematically reviewed the literature to identify PROMs for cough in ILD, examining their psychometric properties.

Methods: We searched four databases from inception to 10 January 2025. English-language original articles that described the use of a PROM to measure cough in adults with ILD and addressed the psychometric properties, method of administration or results of usability testing were selected.

Results: 21 PROMs were evaluated in 35 studies, including 14 in idiopathic pulmonary fibrosis (IPF) and seven in other ILDs, eight cough-specific PROMs, and 13 disease-specific PROMs with a domain for cough. No tool had sufficient evidence for more than 5/7 of the psychometric properties evaluated. There was evidence for content validity for four PROMs in IPF (A Tool to Assess Quality of Life in Idiopathic Pulmonary Fibrosis (ATAQ-IPF), the Cough and Sputum Assessment Questionnaire (CASA-Q), Evaluating Respiratory Symptoms: COPD (E-RS™:COPD) and the Living with Idiopathic Pulmonary Fibrosis Questionnaire (L-IPF)). Only one study evaluated convergent validity using objective cough monitoring, demonstrating high validity for the Leicester Cough Questionnaire (LCQ) (r=-0.74- -0.80) and cough visual analogue scale (VAS) (r=0.80). Acceptable internal consistency (α>0.7) was demonstrated for 10 PROMs (ATAQ-IPF, the Cross-Atlantic modification of ATAQ-IPF, the Chinese version of ATAQ-IPF, CASA-Q, E-RS™:COPD, LCQ, L-IPF, the IPF-specific version of St George's Respiratory Questionnaire (SGRQ), the modified version of the Edmonton System Assessment System and SGRQ). The cough VAS demonstrated good predictive validity and L-IPF was responsive to ILD-specific therapies, with effect sizes ranging from 0.32 to 0.44.

Conclusion: Evidence supporting the measurement properties of available PROMs for cough in ILD is limited. Further validation of existing instruments and the development of new disease-specific PROMs are needed.