Disease Activity in Psoriatic Arthritis: Comparison of the Discriminative Capacity and Construct Validity of Six Composite Indices in a Real World

Abstract

Objective. To compare, “in a real world,” the performance of the most common composite activity indices in a cohort of PsA patients. Methods. A total of 171 PsA patients were involved. The following variables were evaluated: peripheral joint assessment, patient reported of pain, physician and patient assessments of disease activity, patient general health status, dactylitis digit count, Leeds Enthesitis Index, Health Assessment Questionnaire (HAQ), physical and mental component summary score of the Medical Outcome Survey (SF-36), Psoriasis Area and Severity Index (PASI), Dermatology Life Quality Index, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR). To measure the disease activity, the Disease Activity Score (DAS28-ESR and DAS28-CRP), Simple Disease Activity Index (SDAI), Composite Psoriatic Disease Activity Index (CPDAI), disease activity in psoriatic arthritis (DAPSA), and Psoriatic Arthritis Disease Activity Score (PASDAS) have been calculated. The criteria for minimal disease activity (MDA) and remission were applied as external criterion. Results. The ROC were similar in all the composite measures. Only the CPDAI showed less discriminative ability. There was a high degree of correlation between all the indices (P < 0.0001). The highest correlations were between DAPSA and SDAI (rho = 0.996) and between DAPSA and DAS28-CRP (rho = 0.957). CPDAI, DAPSA, and PASDAS had the most stringent definitions of remission and MDA category. DAS28-ESR and DAS28-CRP had the highest proportions in remission and MDA. Conclusions. Although a good concurrent validity and discriminant capacity of six disease activity indices were observed, the proportions of patients classified in the disease activity levels differed. In particular, the rate of patients in remission was clearly different among the respective indices.

Defining remission and treatment success using the DAPSA score: response to letter by Helliwell and Coates

“…The authors’ worry is also dismissed in a study by Husic et al who showed that DAPSA remission (using a cut point close to that determined here) had much higher specificity for sonographic remission than MDA or the Composite Psoriatic Disease Activity Index (CPDAI) 14. Moreover, independently of our study, Salaffi et al 15 found a DAPSA score of 4 to be a cut point for remission and the specificity of the DAPSA to be almost 90%, higher than that of the CPDAI or the Psoriatic Arthritis Disease Activity Score (PASDAS). All these independent data contradict the authors’ theoretical concerns.…”

Discordance between tender and swollen joint count as well as patient's and evaluator's global assessment may reduce likelihood of remission in patients with rheumatoid arthritis and psoriatic arthritis: data from the prospective multicentre NOR-DMARD study

“…The following remission criteria were explored: (1) DAS28<2.6,15 (2) SDAI≤3.3,16 17 (3) CDAI≤2.8,16 (4) American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) Boolean (28 tender joint count, 28 swollen joint count, patient's global assessment (0–10 scale), CRP (mg/dL), all ≤1),16 (5) modified DAPSA<4 18…”

Treat-to-target as an approach in inflammatory arthritis

“…peripheral spondyloarthritis) to the target of remission or minimal or low disease activity [66]. In the meantime, the Disease Activity index for PsA has been further validated [67,68] and provides not only a continuous disease activity scale, but now also definitions of disease activity states, including remission [69]. Most importantly, however, the first study [70 && ] targeting a state of low ('minimal') disease activity, Tight Control Of Psoriatic Arthritis, was recently published, confirming the assumption of the T2T-SpA (Spondyloarthritis) task force that a targeted treatment approach was superior to routine care also in PsA.…”