PsA Remission, Response Cutoffs Identified for DAPSA Tool

Janis C. Kelly

August 31, 2015

A new, fast clinical tool for monitoring psoriatic arthritis (PsA) remission and treatment success was reported based on the Disease Activity Index for Psoriatic Arthritis (DAPSA) without measuring C-reactive protein (CRP), referred to as cDAPSA. The researchers identified cut points for remission; low, moderate, and high PsA disease activity; and definitions of minor, moderate, and major treatment response.

Monika M. Schoels, MD, from the Second Department of Internal Medicine, Hietzing Hospital, Vienna, Austria, and colleagues report the results in an article published online August 12 in the Annals of the Rheumatic Diseases.

Senior author Josef S. Smolen, MD, chair of the Division of Rheumatology at the Medical University of Vienna in Austria and chair of the Second Department of Medicine at the Center for Rheumatic Diseases at Hietzing Hospital, told Medscape Medical News that cDAPSA is particularly useful in practice because it is easy to calculate and can be used immediately, without the need for serum analysis.

"It is untransformed and unweighted, and thus there is no need for a calculator, let alone an electronic device," he said.

"To our knowledge, DAPSA is the only composite disease activity measure that has been developed specifically for [PsA] (rather than borrowed from rheumatoid arthritis) and now provides distinct cut points for all disease activity states, from remission via low and moderate to high disease activity. In addition, Dr Schoels has derived minor, moderate, and major response criteria. All these data were validated in our study," added Dr Smolen.

Cut Points for Disease Activity and Therapeutic Response

The original DAPSA score resulted from adding five variables: tender and swollen joints (TJC68, SJC66), patient global assessment and patient pain assessment (each on a 10-cm visual analogue scale [VAS]), and CRP. The DAPSA score in this study (cDAPSA) excluded CRP, similar to the way the Clinical Disease Activity Index was developed from the Simplified Disease Activity Index used in rheumatoid arthritis.

The researchers asked 44 international rheumatology experts to classify 30 patients from an observational database into disease states (remission or REM, low-activity or LDA, moderate activity or MDA, high activity or HDA), based on SJC66, TJC68, patient global activity and pain ratings on VAS, and CRP levels. They calculated the 25th and 75th percentiles of each DAPSA category, which were used to define the DAPSA cut points.

Next, the researchers used patient-level data from the Adalimumab Effectiveness in Psoriatic Arthritis Trial (ADEPT), Infliximab Multinational Psoriatic Arthritis Controlled Trial (IMPACT), and Golimumab—A Randomized Evaluation of Safety and Efficacy in Subjects with Psoriatic Arthritis Using a Human Anti-TNF Monoclonal Antibody (GO-REVEAL) randomized controlled clinical trials to determine which percentage change of DAPSA best agreed with American College of Rheumatology 50% (ACR50) and ACR70 responses. These were defined as "DAPSA moderate" and "DAPSA major" responses.

The authors write, "Mean DAPSA differed significantly between patients classified as REM, LDA, MDA or HAD (p<0.001). Based on the distributions of DAPSA in these groups, we propose cut-off values of ≤4 for REM, >4 and ≤14 for LDA, >14 and ≤28 for MDA and >28 for HDA. We observed best agreement with ACR20/50/70-response at DAPSA changes of 50/75/85%, reflecting minor, moderate and major improvement."

The proposed definitions are minor response, 50% change in DAPSA; moderate response, 75% change; and major response, 85% change.

In addition to routine clinical use, Dr Smolen suggested the new criteria might be useful in clinical trial design: "They will allow distinction of different response levels and will allow targeting low disease activity or remission as requested in the treat-to-target recommendations; further, they will allow [us] to define inclusion and exclusion criteria," he said.

Is Joint Activity Enough to Judge PsA?

The authors contend that focusing on joint activity and systemic levels of inflammation is a reasonable way to evaluate PsA outcomes. Dr Smolen said, "This is the only composite score that focuses solely on the arthritic component of psoriatic disease. We do not feel that mixing joint disease with enthesitis or skin or other manifestations is helpful but, rather, blurs potential treatment effects that often differ between different manifestations.” He also noted that other scoring systems already exist of these other symptom areas, including the Psoriasis Area Severity Index for the skin and the Maastricht Ankylosing Spondylitis Enthesitis Score for enthesitis. “[T]hrowing these manifestations together, in our view, is anything but useful. Also, we do not know if all these manifestations are caused by the same pathogenetic pathways; indeed, given differential responses with certain therapies, it must be assumed that these mechanisms differ."

However, other PsA experts are less convinced.

Laura Coates, MD, National Institute for Health Research Clinical Lecturer, University of Leeds, United Kingdom, and visiting assistant professor, University of Rochester, New York, told Medscape Medical News, "I think the DAPSA is useful, as it's easy and feasible to perform in clinical practice and easy to calculate. However, I have a major concern that it doesn't include any other measures of PsA. We know that many patients have active enthesitis, dactylitis, skin disease, nail disease, and axial disease, and all of these things are not measured by the DAPSA. This is a major limitation of the DAPSA, and means that if clinicians use it in practice in a 'treat to target' approach, they will not assess (or treat) any of these other features of PsA. This would lead to an adverse effect on many patients."

Dr Coates also noted that the clinical trial data used to develop the response criteria and cutoffs were from studies in which patients were selected to have predominantly articular and polyarticular disease. She suggested that other validated composite measures and response criteria could be used for a treat-to-target approach, such as the Minimal Disease Activity criteria, the Psoriatic Arthritis Disease Activity Score, and the Composite Psoriatic Disease Activity Index.

"Smolen et al in this paper mention these as being too complex, but to simplify PsA just to articular disease is to do a disservice to patients," Dr Coates said. "The [Minimal Disease Activity] criteria can be completed in a 5- to 10-minute consultation, which is feasible in normal clinical practice, and these include assessment of skin, enthesitis, and key patient reported outcomes such as pain and physical function."

Philip Helliwell, MD, from the Leeds Institute of Rheumatic and Musculoskeletal Medicine at the University of Leeds, United Kingdom, agreed. Dr Helliwell, who led the GRACE project for the development of candidate composite disease activity and responder indices for PsA, told Medscape Medical News, "The DAPSA is one of many new composite indices for PsA. It measures articular disease only, so to my mind it is a nonsense to say someone is in remission, or low disease, on the basis of the joints only. Suppose their skin is bad, or they have enthesitis, or axial involvement. That is why we developed measures to assess the whole spectrum of disease."

The authors, Dr Coates, and Dr Helliwell have disclosed no relevant financial relationships.

Ann Rheum Dis. Published online August 12, 2015. Abstract

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