Background Psoriatic arthritis (PsA) is underdiagnosed in primary care, and can be difficult to distinguish from osteoarthritis. Accumulating evidence suggests that diagnostic delay is associated with poorer functional outcome despite treatment.
Objectives To develop a better understanding of the diagnostic delay and burden of disease in patients with PsA, and to investigate management within the first three months of diagnosis.
Methods Data were analysed on all participants with a final diagnosis of PsA from The National Clinical Audit for Rheumatoid and Early Inflammatory Arthritis, undertaken by the British Society for Rheumatology and commissioned by the Healthcare Quality Improvement Programme, recruited between 1/2/2014 and 30/10/2015. Data were collected from patients and clinicians at baseline and three months. 1016 participants with PsA (mean age 49.4±14.5 years; 54% female) were matched 1:1 by age and sex with participants with Rheumatoid Arthritis (RA).
Results Patients with PsA had a significantly longer delay to presentation and diagnosis than those with RA (p<0.02, Table 1), and this remained significant when adjusted for age, sex, ethnicity and social status.
PsA patients had lower median tender (4.0 vs 7.0) and swollen (3.0 vs 5.0) joint counts and lower mean baseline ESR (21.9 vs 27.8 mm/hr) and CRP (16.2 vs 24.2 mg/L) values than patients with RA (p<0.01 for all comparisons), and this remained significant when adjusted for potential confounders. Mean baseline scores for the Inflammatory Arthritis Impact of Disease (IAID) questionnaire were lower in patients with PsA (5.34±2.25 vs 5.94±2.35 in RA, lower scores indicating less impact), although this was not statistically significant when adjusted for demographics and disease activity (p=0.36). There was no significant difference between physical function at baseline between the groups (median HAQ 0.88 PsA vs 1.13 RA, p=0.70).
At follow-up, patients with PsA had significantly higher mean IAID scores (4.32±2.60 vs 3.78±2.56, P<0.05). In those with paired results, the mean improvement in IAID score was 1.32 (95% CI 0.99–1.65) in PsA vs 2.37 (95% CI 2.07–2.67) in RA. In patients with high disease activity at baseline (DAS28 >5.1) a good EULAR response was seen in only 21.4% in PsA vs 30.3% in RA. There was a marked difference in the DMARDs initially prescribed, and the differences remained significant when only those with a DAS28 score indicating moderate or high disease activity at presentation were analysed, as shown in Figure 1.
Conclusions This study demonstrates that patients with PsA have a longer delay to diagnosis between both symptom onset and presentation to primary care, and referral to secondary care and diagnosis than those with RA. Despite similar disease impact and physical function at diagnosis, patients with PsA are less likely to receive combination DMARD treatment, and have increased disease burden at three months.
Disclosure of Interest None declared