Evaluation of patient-based disease activity score (PDAS) in the Japanese rheumatoid arthritis patient registry (NinJa registry)

Objective Patient-reported outcomes (PROs) should be regarded as an important factor in the management of rheumatic diseases. The Patient-based disease activity score (PDAS) was developed as a clinically reliable composite measure for evaluating PROs in rheumatoid arthritis (RA) patients. To replicate and further characterize PDAS, we analyzed PDAS and its clinical relevancy in the National Database of Rheumatic Diseases in Japan (NinJa). Methods Clinical data from the 2022 version of NinJa were analyzed. PDAS1 was calculated for each patient, and statistical analyses, including correlation analyses and multiple regression analysis, were conducted to evaluate the relationship between PDAS1 and other clinical measures. Propensity score (PS) matching was used to compare patients treated with different types of disease-modifying anti-rheumatic drugs (DMARDs). Results The number of included patients was 11983. PDAS1 demonstrated strong correlations with DAS28(ESR) (R = 0.89, p< 2.2x1016) and CDAI, indicating its utility in assessing disease activity. The majority of patients (71.8%) achieved PDAS1-defined remission, aligning closely with DAS28 and CDAI remission. PDAS1 was significantly associated with serum rheumatoid factor (RF) titers (R = 0.25, p< 0.001), and RF-positive patients exhibited higher PDAS1 scores. Notably, PS matched comparison revealed that PDAS1 was lower in patients treated with IL-6 inhibitors, compared with those treated with TNF inhibitors, reflecting differences in lower patient global assessment. Conclusion PDAS1 is a reliable and useful tool for evaluating both disease activity and the functional state of RA patients, particularly from the perspective of PROs. Additionally, PDAS1 can be used for conducting clinical studies in RA patients.