Psychometric properties of the St George's Respiratory Questionnaire in patients with idiopathic pulmonary fibrosis.

The St George's Respiratory Questionnaire (SGRQ) has been used to measure health-related quality of life (HRQoL) in patients with idiopathic pulmonary fibrosis (IPF).This analysis evaluated the psychometric properties of the SGRQ using data from 428 patients with IPF who participated in a 12-month, randomised, placebo-controlled phase II trial of nintedanib.Internal consistency (Cronbach's α) was 0.91 for SGRQ total and >0.70 for domain scores. Test-retest reliability (intraclass correlation coefficients) was 0.77, 0.77, 0.69 and 0.66 for SGRQ total, activity, impact and symptoms scores, respectively. Construct validity of SGRQ total and domain scores was supported by weak to moderate cross-sectional correlations with the Medical Research Council dyspnoea scale (0.32-0.55), 6-min walk test distance (-0.25- -0.34), percentage predicted forced vital capacity (-0.11- -0.15) and measures of gas exchange (-0.26-0.03). There was some evidence that the SGRQ total score was sensitive to detecting change.The reliability, construct validity and responsiveness of the SGRQ in patients with IPF suggest that this is an acceptable measure of HRQoL in patients with IPF.