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Objective. To determine the prevalence of psoriatic arthritis (PsA) using the ClASsification criteria for Psoriatic ARthritis (CASPAR) for classification. Methods. People with psoriasis were identified from the computerized morbidity indices of 2 large UK general practices, total population 22,500. Questionnaires were mailed to all 633 patients thus identified. Of the respondents, a 50% sample was assessed clinically and a proportion had blood samples and radiographs taken. Patients labeled as having psoriasis were also cross-referenced with a local secondary care morbidity index for PsA and rheumatoid arthritis. Figures for the prevalence of PsA were estimated from these data. Results. One hundred sixty-eight questionnaires were returned (response rate 27%) and 93 people (55% of questionnaire respondents) were examined. Of these 93 people, 12 (4 of whom were cross-referenced to the hospital database) were thought to have PsA clinically, all fulfilling the CASPAR criteria for PsA. Six of the 93 examined patients did not have psoriasis or a family history of psoriasis and had no historical features or clinical signs of psoriasis on interview and examination. Extrapolating from the data of those people actually examined, the estimated (corrected) prevalence was 13.8% (95% confidence interval 7.1-24.1%). Conclusion. The estimated prevalence of PsA in this population, using the CASPAR criteria, was 13.8%. Misclassification of psoriasis and arthritis, and response bias, indicate that this is probably an overestimate.

Objective-In 1971 McEwen and colleagues suggested that the radiological changes of classic ankylosing spondylitis (AS), and the changes of the spondylitis associated with inflammatory bowel disease diVer in several respects from the radiological features of psoriatic and reactive spondylitis. The findings of this study have never been confirmed. The aim of this study was to replicate the McEwen study comparing films blinded to diagnostic group. Methods-The study population comprised 91 patients with classic AS, 15 patients with regional enteritis, 16 patients with ulcerative colitis, five patients with sexually acquired reactive arthritis, two with postdysenteric arthritis, and 34 with psoriatic arthritis. Blinded reading of spinal radiographs was undertaken, scoring for severity, symmetry, paravertebral ossification, size of syndesmophytes, ligamentous calcification, squaring, discitis, pseudofractures, zygoapophyseal joint involvement, and complete ankylosis. Results-Comparisonof the four groups-classic, enteropathic, psoriatic, and reactive AS-showed diVerences with respect to symmetry of sacroiliitis, symmetry of lumbar spinal involvement, and frequency and size of syndesmophytes. Zygoapophyseal joint involvement was more frequent in the lumbar spine in classic and enteropathic spondylitis but no between group diVerences were found with respect to symphisitis, squaring, apophyseal joint involvement and ligamentous calcification in the lumbar spine, and other areas. Conclusions-Some of the radiological diVerences described by McEwen et al, notably the asymmetry, the less severe changes, and the distinctive syndesmophytes in psoriasis, have been confirmed. A number of hypotheses are proposed to explain these diVerences including biomechanical, biochemical, and genetic factors.

A distinctive peripheral arthropathy associated with psoriasis is well recognized, the classical pattern describing an asymmetrical oligoarthritis with predominant distal interphalangeal joint (DIP) involvement. There is some dispute about the frequency of this classical pattern and of the pattern of symmetrical polyarthritis resembling rheumatoid arthritis. Some of the dispute may be a result of loose definitions. In this clinical and scintigraphic study of 50 patients with psoriatic arthritis we have used tighter definitions of disease pattern and have found that 68% of this group had a symmetrical polyarthritis similar to that found in rheumatoid arthritis. Yet, arthritis associated with psoriasis differs from rheumatoid arthritis in a number of ways including the pattern of joint involvement, extra-articular osseous features, and radiological changes. Scintigraphic changes in psoriatic arthritis suggest that subclinical involvement of the manubriosternal and sternoclavicular joints is common, suggesting an association between psoriasis vulgaris and arthro-osteitis. A modified classification of the osteoarticular manifestations of psoriasis is proposed.

ObjectiveEvaluation of the efficacy and safety of guselkumab, a human monoclonal antibody targeting the interleukin-23p19 subunit, in patients with psoriatic arthritis (PsA) through 1 year.MethodsAdults who met ClASsification criteria for Psoriatic ARthritis, with active disease (≥3 swollen and ≥3 tender joints; C reactive protein ≥0.3 mg/dL) despite standard treatment (31% previously received ≤2 tumour necrosis factor inhibitors (TNFi)), were randomised (1:1:1) to guselkumab 100 mg every 4 weeks (Q4W); guselkumab 100 mg at Week0, Week4, then Q8W; or placebo with cross-over to guselkumab 100 mg Q4W at Week24 (PBO→Q4W) through Week48. Clinical efficacy through Week52 (employing non-responder imputation) and adverse events (AEs) through Week60 were evaluated.ResultsOf 381 treated patients, 90% completed the study. Numerical increases in the proportions of patients achieving ≥20% improvement in ACR criteria (ACR20) were observed post-Week24, reaching 73% (94/128) and 60% (76/127) for Q4W-randomised and Q8W-randomised patients, respectively, by Week52. Proportions of patients achieving ACR50/ACR70/skin responses and minimal/very low disease activity were maintained, as were improvements in physical function and health-related quality of life, through Week52 in guselkumab-randomised patients. Response to guselkumab was maintained in both TNFi-naïve and TNFi-experienced patients. Serious AEs and serious infections occurred in similar proportions of guselkumab Q4W-randomised (3% and 0%) and Q8W-randomised (6% and 2%) patients through Week60, with no new safety concerns versus observations through Week24. No guselkumab-treated patient and two patients receiving placebo died; no study participant developed opportunistic infection or inflammatory bowel disease.ConclusionGuselkumab provided sustained improvement across multiple clinical manifestations of PsA, maintaining a favourable benefit-risk profile, through 1 year regardless of prior TNFi exposure.