Comparison of Composite Measures of Disease Activity in Psoriatic Arthritis Using Data From an Interventional Study With Golimumab

Objective To compare the performance of the Psoriatic Arthritis Disease Activity Score (PASDAS), the Arithmetic Mean of the Desirability Function (AMDF), the Composite Psoriatic Disease Activity Index (CPDAI), and the Disease Activity Index for Psoriatic Arthritis (DAPSA) in the GO-REVEAL data set. The Disease Activity Score using 28 joints (DAS28) was used as a comparator. Methods The GO-REVEAL study did not allow full computation of all the composite scores (a modified version of CPDAI was used). The performance of the scores at baseline and followup (weeks 14 and 24) was compared using effect sizes. Results All indices could distinguish response to treatment at 14 and 24 weeks. Effect sizes at 24 weeks for the 50 mg (100 mg) golimumab doses were 2.18 (2.36), 2.08 (2.36), 1.09 (1.41), 1.80 (1.78), and 1.13 (1.18) for PASDAS, AMDF, modified CPDAI, DAS28, and DAPSA, respectively. Comparison of 24-week values across the 3 treatment groups (placebo, golimumab 50 mg, and golimumab 100 mg) by an analysis of covariance using the baseline values as covariates gave the following F statistics: PASDAS 18.3, AMDF 19.6, modified CPDAI 9.4, DAS28 13.6, and DAPSA 7.9; all of these are highly significant. When the analysis was confined to the 2 golimumab treatment groups, there were no significant between-treatment group differences with any of the composite measures. Conclusion PASDAS and AMDF were better able to distinguish treatment effect, having larger effect sizes at 24 weeks. PASDAS, AMDF, and modified CPDAI better reflected domains such as skin, enthesitis, and dactylitis.