Validation of the IPF-specific version of St. George’s Respiratory Questionnaire

Abstract

Background Patients with idiopathic pulmonary fibrosis (IPF) have impaired health-related quality of life (HRQL). To measure HRQL, an IPF-specific version of the St. George’s Respiratory Questionnaire (SGRQ-I) was developed, but not sufficiently validated. This study aimed to assess the validity (i.a. known-groups validity and concurrent validity) and test-retest reliability of SGRQ-I in IPF patients with different disease durations. Methods Patients with IPF were consecutively recruited and completed SGRQ, SGRQ-I, King’s Brief Interstitial Lung Disease questionnaire (K-BILD), University of California, San Diego Shortness of Breath Questionnaire (SOBQ) and Short Form-36 (SF-36) along with pulmonary function tests and a 6-min walk test (6MWT) at baseline. After two weeks, SGRQ-I and Global Rating of Change Scales (GRCS) were completed. Results At baseline and after two weeks, 150 and 134 patients completed the questionnaires, respectively. The internal consistency of SGRQ-I was high (Cronbach’s α = 0.92). Good concurrent validity was demonstrated by high intraclass correlation coefficients (ICC = 0.97), Bland-Altman plots and moderate to strong correlations to K-BILD, SOBQ and SF-36 (r = − 0.46 to 0.80). High ICC (0.92) and a Bland-Altman plot indicated good test-retest reliability. SGRQ-I was good at discriminating between patients with different stages of disease (Δscore > 18.1, effect sizes > 0.10). Validity was similar across groups of different disease duration. Conclusions SGRQ-I proved to be valid at distinguishing between different disease severities, valid compared to other HRQL instruments, applicable across different disease durations and reliable upon repetition. SGRQ-I is a valid option for measuring HRQL in patients with IPF. Trial registration The study was registered at clinicaltrials.org ( NCT02818712 ) on 15 June 2016. Electronic supplementary material The online version of this article (10.1186/s12931-019-1169-9) contains supplementary material, which is available to authorized users.

Responsiveness and minimal clinically important difference of SGRQ-I and K-BILD in idiopathic pulmonary fibrosis

“…As a result of measurement error on two measures, correlations between changes in scores are expected to be smaller. This may explain the generally weaker correlations in this longitudinal study compared to the cross-sectional studies on SGRQ-I and K-BILD [7][8][9][10]. DLCO showed the weakest associations to SGRQ-I and K-BILD in both analyses.…”

“…Both methods indicated that SGRQ-I and K-BILD responded to changes in all HRQL and most physiological anchors; scores of the two instruments changed in concordance with changes in the anchors. The weaker correlations to physiological than to HRQL anchors were expected, as cross-sectional studies of K-BILD and SGRQ-I have shown similar results [7][8][9][10]. As a result of measurement error on two measures, correlations between changes in scores are expected to be smaller.…”

“…Exclusion was based on linguistic or intellectual barriers preventing completion of the questionnaires. Other studies on K-BILD and SGRQ-I have been based on the same cohort of patients with IPF [8,10].…”

“…A modified version of Saint George's Respiratory Questionnaire (SGRQ) was developed for patients with IPF (SGRQ-I) [7,8]. To our knowledge, no studies have examined responsiveness or MCID of SGRQ-I, and assessment of the longitudinal validity of SGRQ-I is important before implementing the instrument in clinical trials or daily practice.…”

Chinese herbal medicines for the treatment of cough in idiopathic pulmonary fibrosis

“…Cough-related QOL, assessed by cough questionnaires including not limited to cough visual analogue scale (VAS), [ 21 ] Leicester cough questionnaire (LCQ), [ 22 ] Cough Quality of Life Questionnaire (CQLQ), [ 4 ] St. Georges Respiratory Questionnaire (SGRQ). [ 23 ]…”