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We truly appreciate the comments on our study of Disease Activity Index for Psoriatic Arthritis (DAPSA) disease activity states and DAPSA responses provided by Drs. Helliwell and Coates,1 because this gives us a dual opportunity: first, to address the principal differences in our thinking on psoriatic arthritis (PsA) compared with that of the authors of the letter, and second to expand on our findings. The authors, whose work we have followed and valued highly for many years, present a large number of comments that we will try to answer individually.
Concerns about only assessing joints. The authors ought to take notice that the DAPSA is not solely comprised of joint counts, but, aside from C-reactive protein (CRP), also includes patient global assessment (PtGA) as well as patient pain assessment (PtP).
Cut-offs were developed based entirely on physician opinion without including patients. While we sent our survey only to physicians, it needs to be borne in mind that the DAPSA includes PtGA and PtP and thus is already heavily weighted with the views of the patient. This item is again mentioned as being ‘disappointing’ toward the end of the letter. However, we were partly inspired by the authors themselves who stated in their publication on the definition of moderate disease activity (MDA) that the “questionnaire … was then circulated to rheumatologists and dermatologists with an interest in PsA, identified through membership of GRAPPA”,2 without involving patients. To us it seemed preferable to obtain the patients‘ opinions on cut points and responses in a separate currently evolving activity. This will enable involving a large number of patients, rather than adding a few patients to the survey as suggested by the authors.
Response criteria used randomised controlled trial (RCT) datasets rather than data from the PsA population as a whole. In …