Development and initial validation of a disease-specific instrument to measure health-related quality of life in hypersensitivity pneumonitis

Rationale and objective Disease-specific health-related quality of life (HRQOL) instruments enable us to capture domains that are most relevant to specific patient populations and are useful when a more individualised approach to patient assessment is desired. In this study, we assessed the validity and reliability of the first instrument specifically developed to measure HRQOL in hypersensitivity pneumonitis (HP). Methods A 39-item HP-HRQOL instrument and several anchors were collected from a cohort of patients with HP. Exploratory factor analysis and item reduction were utilised to construct a shortened version of the instrument. Several validity and reliability analyses were conducted on this version of the HP-HRQOL. Measurements and main results 59 patients with HP completed the study. The revised HP-HRQOL instrument comprises 15 items composing two factors (domains): 1) impacts on daily life; and 2) mental wellbeing. Internal consistency reliability was strong for Factor 1 (Cronbach's α=0.94, 95% CI 0.92–0.96) and Factor 2 (Cronbach's α=0.89, 95% CI 0.85–0.94). Test–retest reliability was strong (ICC 0.94, 95% CI 0.89–0.97). The HP-HRQOL strongly correlated with other validated patient-reported outcome measures and moderately correlated with % predicted forced vital capacity. The HP-HRQOL distinguished between those with different severities of HP as determined by lung function and supplemental oxygen use. Conclusions The HP-HRQOL, the first patient-reported outcome instrument specific to adults with HP, possesses strong validity and reliability characteristics for measuring disease-specific HRQOL and distinguishes among patients with different severities of disease.