Minimal Detectable Changes of the HAQ-DI, PROMIS-29v2.0 Domains, and PHQ-8 in Systemic Sclerosis: A SPIN Cohort Cross-Sectional Study.

OBJECTIVE: Systemic sclerosis (SSc) is a rare, chronic, autoimmune disorder associated with disability, diminished physical function, fatigue, pain, and mental health concerns. We assessed minimal detectable changes (MDCs) of the Health Assessment Questionnaire-Disability Index (HAQ-DI), Patient Reported Outcomes Measurement Information System-29 Profile version 2.0 (PROMIS-29v2.0) domains, and Patient Health Questionnaire-8 (PHQ-8) in SSc.

METHODS: Scleroderma Patient-centered Intervention Network Cohort participants completed the HAQ-DI, PROMIS-29v2.0 domains, and PHQ-8 at baseline assessments from April 2014 until August 2023. We estimated MDC95 and MDC90 with 95% confidence intervals (CI) generated via the percentile bootstrapping method resampling 1000 times. We compared MDC estimates by age, sex and SSc subtype.

RESULTS: A total of 2,571 participants were included. Most were female (N = 2,241; 87%), and 38% (N = 976) had diffuse SSc. Mean (SD) age was 54.9 (12.7) years and duration since onset of first non-Raynaud phenomenon symptom 10.8 (8.7) years. MDC95 estimate was 0.41 points (95% CI: 0.40 to 0.42) for the HAQ-DI, between 4.88 points (95% CI: 4.72 to 5.05) and 9.02 points (95% CI: 8.80 to 9.23) for the 7 PROMIS-29v2.0 domains, and 5.16 points (95% CI: 5.06 to 5.26) for the PHQ-8. MDC95 estimates were not materially different across subgroups.

CONCLUSION: MDC95 and MDC90 estimates were precise and similar across age, sex and SSc subtype groups. HAQ-DI MDC95 and MDC90 were substantially larger than previous estimates of HAQ-DI minimal important difference from several small studies. Minimally important differences of all measures should be evaluated in large studies using anchor-based methods.