Introduction We evaluated the psychometric properties of the St George’s Respiratory Questionnaire (SGRQ) in patients with idiopathic pulmonary fibrosis (IPF) using data from the two INPULSIS trials.
Methods Data from 1061 patients treated with nintedanib or placebo were pooled. Internal consistency, test–retest reliability, construct validity, known-groups validity, responsiveness and responder thresholds were examined.
Results Cronbach’s α was 0.93 for SGRQ total score and >0.75 for domain scores. In patients with stable disease based on change in forced vital capacity (FVC) ≤5% predicted or ‘no change’ on Patient’s Global Impression of Change, intraclass correlation coefficients for the SGRQ total score were 0.72 or 0.76, respectively. Moderate to strong correlations were observed between SGRQ total and domain scores and the Cough and Sputum Assessment Questionnaire cough domains (−0.34 to −0.65), University of California San Diego Shortness of Breath Questionnaire (0.56 to 0.83) and EuroQol 5-Dimensional Quality of Life Questionnaire Visual Analogue Scale (−0.41 to −0.55); correlations with FVC % predicted were weak (−0.24 to −0.30). Longitudinal correlations between changes in SGRQ total score and these patient-reported outcomes over 52 weeks were moderate. Changes in SGRQ total, impact and activity scores were sensitive to detecting improvement or deterioration in FVC >10% predicted at week 52. Collectively, distribution-based and anchor-based approaches suggested using a change of 4–5 points in SGRQ total score as a starting point for responder analyses.
Conclusions The psychometric properties of the SGRQ support its use as a measure of health-related quality of life in patients with IPF.
- interstitial fibrosis
- rare lung diseases
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Contributors All authors were involved in planning the analyses, in the interpretation of data and in drafting the manuscript; met the ICMJE criteria for authorship; were fully responsible for all content and editorial decisions and were involved at all stages of manuscript development and have approved the final version.
Funding This study was funded by Boehringer Ingelheim. Medical writing assistance was supported financially by Boehringer Ingelheim as provided by Julie Fleming and Wendy Morris of FleishmanHillard Fishburn, London, UK during the preparation of this article.
Competing interests JJS has received personal fees from Boehringer Ingelheim and Genentech for talks on IPF and a grant from Genentech for developing educational materials on IPF for patients and caregivers. KKB has received personal fees from AstraZeneca, Bayer, Biogen, Boehringer Ingelheim, FibroGen, Galecto, Gilead, MedImmune, Novartis, Aeolus, ProMetic, Patara, Third Pole and aTyr, as well as grants from Genentech and NHLBI. HW and NKL are employed by Evidera, a healthcare research firm that provides consulting and research services to pharmaceutical, device, government and non-government organisations. Evidera received payment from Boehringer Ingelheim for conducting analyses presented in this manuscript. DE, WS and CSC are employees of Boehringer Ingelheim.
Patient consent Obtained.
Ethics approval An independent ethics committee or institutional review board approved the clinical protocol at each participating centre.
Provenance and peer review Not commissioned; externally peer reviewed.
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