The minimally important difference in clinical practice for patient-centered outcomes including health assessment questionnaire, fatigue, pain, sleep, global visual analog scale, and SF-36 in scleroderma

Abstract

Objective: We studied a large clinical practice and multicenter database to estimate the minimally important difference (MID) in systemic sclerosis (SSc) using global rating of change anchors for the Health Assessment Questionnaire-Disability Index (HAQ-DI) and visual analog scale (VAS) in pain, fatigue, sleep, global status, and the Medical Outcomes Study Short-Form 36 (SF-36) in clinical practice.

Methods: Longitudinal data were collected from a scleroderma clinic on patients with scleroderma (n = 109) who had completed the HAQ-DI and pain/fatigue/sleep/global status VAS (0 to 100 mm) questionnaires at 2 consecutive visits, and rated their change in overall status since the last visit as much better, better, same, worse, or much worse. Data were extracted from the Canadian Scleroderma Research Group (CSRG) database (n = 341) for 2 consecutive annual visits where the patients had completed HAQ-DI and SF-36, and the SF-36 "change in health" item.

Results: For the single site, the mean baseline HAQ-DI was 0.895 and 0.911 at followup, with a mean change of 0.016. The MID estimates for improvement and worsening respectively were -0.0125 (0.125, 75th percentile)/0.042 (0.217, 75th percentile) for HAQ-DI, -8.00/3.61 for pain, -10.00/3.79 (25.32) for fatigue, -18.50/5.92 for sleep, and -6.70/4.05 for global VAS. In the CSRG, baseline scores were 0.787 for HAQ-DI, 37.20 for the Physical Component Summary (PCS) of SF-36, and 48.57 for the Mental Component Summary (MCS). The MID estimates for improvement and worsening were -0.037 (0.250, 75th percentile)/0.140 (0.375, 75th percentile) for HAQ-DI, 2.18/-1.74 for PCS, and 1.33/-2.61 for MCS.

Conclusion: This study provides MID estimates in SSc from 2 large databases for commonly used patient-reported outcomes in a clinical practice setting, which could differ from MID in trials.