articleRemission in psoriatic arthritis : is it possible and how can it be predicted ?

Introduction: Since remission is now possible in psoriatic arthritis (PsA) we wished to examine remission rates in PsA patients following anti tumour necrosis factor alpha (TNFα) therapy and to examine possible predictors of response. Methods: Analysis of a prospective patient cohort attending a biologic clinic, between November 2004 and March 2008, was performed prior to commencing therapy and at regular intervals. Baseline clinical characteristics including demographics, previous disease-modifying antirheumatic drug (DMARD) response, tender and swollen joint counts, early morning stiffness, pain visual analogue score, patient global assessment, C reactive protein (CRP) and health assessment questionnaire (HAQ) were collected. Results: A total of 473 patients (152 PsA; 321 rheumatoid arthritis (RA)) were analyzed. At 12 months remission, defined according to the disease activity score using 28 joint count and CRP (DAS28-CRP), was achieved in 58% of PsA patients compared to 44% of RA patients, significant improvement in outcome measures were noted in both groups (P < 0.05). Analysis of a subgroup of PsA and RA patients matched for DAS28-CRP at baseline also showed higher numbers of PsA patients achieving remission. Linear regression analysis identified the HAQ at baseline as the best predictor of remission in PsA patients (P < 0.001). Conclusions: DAS28 remission is possible in PsA patients at one year following anti-TNF therapy, at higher rates than in RA patients and is predicted by baseline HAQ. Introduction Psoriatic arthritis (PsA) is a chronic inflammatory arthritis, usually seronegative for rheumatoid factor associated with psoriasis [1,2]. The clinical phenotype varies widely, which has led to difficulties with classification, diagnosis and therefore predicting prognosis. Initially, PsA was considered a benign disease, one study suggesting only 11% of patients developed erosions over seven years [3]. However, in the same journal it was highlighted that a number of reports suggested a high occurrence of erosions in between 46 to 62% of patients [4]. The incidence of PsA varies from 5.4 to 42% depending on the report. In a Finnish population based study 46% developed erosions [5] and in another study 62% of patients worsened and the pattern of disease changed over time [6]. Several recent studies, however, suggest PsA is progressive, often disabling and associated with an increased mortality [7]. In a study of PsA, in an early arthritis clinic, it accounted for 13% of new patients and progressive, erosive damage occurred in almost 50% patients in the first two years [8]. In the absence of evidence from randomized clinical trials, Methotrexate (MTX) is generally accepted to be useful for the control of peripheral arthritis, but has little efficacy in spinal disease [9]. In a study of early PsA, however, erosive damage appeared to develop even when MTX therapy was commenced early [8]. This raises the question 'Should anti-TNF agents be introduced early? ' Remission implies the reversibility of functional impairment, minimal or no progression to joint destruction, and at least a theoretic potential to heal a damaged joint [10]. Recent studies suggest remission may now be attainable in rheumatoid arthritis (RA) with the advent of anti-TNF therapy [11], however RA remission has been defined by different criteria (i) DAS28 value of ≤2.6 [12] (ii) imaging no progression on X-ray/Ultrasound/MRI; or (iii) * Correspondence: douglas.veale@ucd.ie 1 Department of Rheumatology, Dublin Academic Medical Centre, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland Full list of author information is available at the end of the article BioMed Central © 2010 Saber et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Saber et al. Arthritis Research & Therapy 2010, 12:R94 http://arthritis-research.com/content/12/3/R94 Page 2 of 6 American College of Rhuematology (ACR) criteria [13]. Drug-induced remission may be defined as minimal or no clinically detectable disease activity in the presence of continuing drug treatment, which is not stopped or interrupted, but is required to retain the remission state [14]. Drug-free remission persists in the absence of medication. In a recent editorial, de Vlam and Lories highlighted that remission may be a possible goal in PsA [15]. In the current prospective study, we specifically examine clinical and laboratory measures of disease activity to estimate remission rates in PsA patients and examine associated predictive factors. Materials and methods We established a biologic outpatient clinic and prospective database to provide close monitoring and follow-up of patients on biologic therapies. Patients commencing Infliximab, Adalimumab and Etanercept were assessed at baseline, 3, 6 and 12 months with clinical examination, swollen joint count (SJC) and tender joint count (TJC), visual analogue scores (VAS) for pain and for patient global, Health Assessment Questionnaire (HAQ). Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were measured and the 28-joint count Disease Activity Score, DAS28 calculated. RA patients fulfilled diagnostic criteria for according to American College of Rheumatology criteria [13], and PsA patients satisfied validated CASPAR criteria [16]. All patients had clinically active disease, with DAS28 > 3.2 points despite conventional DMARD therapy, and were offered treatment with biologic agents. Patients who had previously received biologic therapy were excluded from this analysis. Patients received education prior to commencing biologic therapy and thereafter gave fully informed verbal consent. Details of patient age, gender, diagnosis, disease duration, RF and CCP antibody status were collected. DAS28 which has been validated for use in PsA [17] and RA patients and modified (HAQ) [18] was calculated. DAS28 response was analyzed by change from baseline, and by the European League Against Rheumatism (EULAR) criteria response categories [19]. All treatment was fully in compliance withthe Helsinki Declaration and the analysis was approved by the St. Vincent's University Hospital ethics committee. Statistics Statistical analysis was performed using SPSS 16 for Windows. Clinical data are expressed as median values and range unless otherwise stated. Comparisons of improvement within a disease group at different time points were performed using Wilcoxon Rank Sign test. Chi square test for categorical data and Mann-Whitney U test for continuous data were used to evaluate the statistical significance of the difference between the two independent groups, PsA and RA. Results Demographic characteristics Data were collected and analyzed from a total of 473 patients (152 PsA; 321 RA) over a one-year follow-up period. Baseline describes time of first dose of anti TNF therapy. Baseline characteristics including demographics, clinical and laboratory data are shown in Table 1. These values are expressed as medians (range). As expected from previous cohort studies, the PsA patients tended to be younger, male and had lower joint counts and disease activity scores in comparison to RA patients. PsA patients received Infiximab-13%, Adalimumab-37% and Etanercept-50%, whereas in RA these drugs were used in 6.8%, 56% and 37.2% of patients respectively. The PsA cohort had oligoarticular disease (27.4%) and polyarticular disTable 1: Baseline variables shown in median(range) unless otherwise stated PsA (n = 152) RA (n = 321) P value Age 45(15 to 77) 56(17 to 85) <0.001 Male 47.7% 29.1% <0.001