Defining the minimal important change and meaningful change value of the disease activity index for psoriatic arthritis: a Chinese longitudinal study.

OBJECTIVE:To determine the minimal important change (MIC) and meaningful change value (MCV) of the disease activity index for psoriatic arthritis (DAPSA) and the effect size (ES) of DAPSA. METHODS:This was a retrospective cohort study, recruiting 106 patients who agreed to participate in the research from the Department of Dermatology at Xiangya Hospital between November 1, 2019, and April 1, 2023. An anchor-based method using linear regression analyses was used to determine the MICs and MCVs of the DAPSA. The anchor question assessed whether the patient's well-being had changed since their previous visit, employing a 5-point Likert scale that ranged from 'much improved' to 'much deteriorated'. RESULTS:The overall MIC value was 8.4 (95% CI; 0.01 to 16.75). The MIC improvement was 9.5 (95% CI; 0.89 to 18.14) and MIC deterioration was 1.1 (95% CI; -9.81 to 12.05). The overall MCV was 10.5 (95% CI; 4.34 to 16.72). MCV improvement was 11.4 (95% CI; 5.95 to 16.95), MCV deterioration was 1.1 (95% CI; -9.81 to 12.05). The SE was 0.6. CONCLUSION:MIC, offering physicians an additional means to contextualize the patient's perception of disease activity during treatment, and a change of 10.5 is likely to be regarded as a clinically meaningful change, enhancing the utility of DAPSA in PsA clinical trials.