The minimal important difference for the St George's Respiratory Questionnaire in patients with severe COPD

Abstract

The St George's Respiratory Questionnaire (SGRQ) is a validated, commonly used questionnaire for measuring quality of life in patients with chronic obstructive pulmonary disease (COPD). The current established minimal important difference (MID) for SGRQ scores in an average COPD population is −4 units. However, for patients with severe COPD, the MID has not been thoroughly validated. We re-determined the SGRQ MID for this patient group.115 severe COPD patients (forced expiratory volume in 1 s (FEV1) 26±9% of predicted, SGRQ score 62 ±11 units; mean±SD,) who participated in seven different bronchoscopic lung volume reduction clinical trials were included in the analysis. Anchor-and distribution-based methods were used to define the MID for SGRQ scores. FEV1, 6-min walk distance and residual volume were used as anchors.Combining both anchor-and distribution-based methods, we identified a SGRQ MID of −8.3 units at 1 month and −7.1 units at 6 months.This study proposes an alternative SGRQ MID for patients with severe COPD of −8.3 units at 1 month and −7.1 units at 6 months follow-up after intervention. Our new MID estimates could be applied for both interpreting SGRQ outcomes as well as sample size determination in future clinical trials investigating interventions in severe COPD patients. @ERSpublicationsIn patients with severe COPD the redefined MID for SGRQ is -8.3 units at 1 month and -7.1 units at 6 months

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“…Significant negative correlation between FEV 1 % pred and all components (Symptoms, Impacts, Activity) and the total score of SGRQ was previously described in a cohort of Hispanic smokers 45. Similarly, in another study, significant negative correlation between FEV 1 % pred and the Total score was described in a sample of severe COPD patients ( r =−0.4, P <0.001) 46. In a double-blind placebo-controlled study designed to assess the benefits of the fixed combination inhaler fluticasone propionate and salmeterol versus placebo, the longitudinal analysis of data for 4,951 COPD patients showed significant negative correlation regarding the change in SGRQ scores and FEV 1 during the 3 years of the study in all treatment arms, combined 47.…”

One-Year Follow-Up after Endobronchial Valve Treatment in Patients with Emphysema without Collateral Ventilation Treated in the STELVIO Trial

“…Clinical response was defined using established minimal clinically important differences (MCID) for FEV 1 : 10% [12] , residual volume (RV): -430 mL [13] , 6MWD: 26 m [14] , and SGRQ: -4 points [15] and -7 points [16] .…”

Interpreting patient-reported outcomes from clinical trials in COPD: a discussion

“…This was the case with the SGRQ; in the two COPD studies used to calculate the MCID,14,15 the baseline scores fell in the same range as that seen in clinical trials (typically 40–55 units). A recent study in patients with COPD who had more severe disease than those usually studied (baseline mean SGRQ total score of 62) recalculated higher values for the SGRQ MCID (−8.3 at 1 month and −7.1 at 6 months) 16. Unfortunately, the authors did not use the methodology used to derive the MCID in a moderately severe population, so it is not possible to conclude from their analysis whether a higher MCID should be used for more severe patients 16.…”

“…A recent study in patients with COPD who had more severe disease than those usually studied (baseline mean SGRQ total score of 62) recalculated higher values for the SGRQ MCID (−8.3 at 1 month and −7.1 at 6 months) 16. Unfortunately, the authors did not use the methodology used to derive the MCID in a moderately severe population, so it is not possible to conclude from their analysis whether a higher MCID should be used for more severe patients 16. Intuitively, a higher MCID for more severe patients appears incorrect, since such patients may be more aware of the benefits of small improvements than patients with milder disease.…”