Elevated CRP even at the first visit to a rheumatologist is associated with long-term poor outcomes in patients with psoriatic arthritis

Objectives Little is known about the long-term association of CRP levels during psoriatic arthritis (PsA) disease course. In this study, we examined whether raised CRP over the disease course is associated with worse outcome measures in a well-characterised PsA cohort with a long-term follow up. Methods A cohort of 283 PsA patients (fulfilling CASPAR criteria) was evaluated. All underwent detailed skin and rheumatologic assessments. Moreover, we documented the presence/absence of comorbidities using Charlson Comorbidity Index (CCI). CRP at first visit to a rheumatologist was documented. Cumulative inflammation over time was represented by the cumulative averages of CRP (ca-CRP). Multiple linear regression modelling CRP was used. Results Two hundred eighty-three PsA patients attended for detailed assessments. A total of 56.5% (n = 160) of the cohort had raised CRP at their first visit to our rheumatology department, and this was significantly associated with long-term erosions, sacroiliitis, PsA requiring TNFi, and high comorbidity Index, on logistic regression analysis. Moreover, 24% (n = 69) of the cohort never had raised CRP during their long-term follow-up, and on logistic regression analysis, such patients had significantly milder disease with fewer erosions, less sacroiliitis and fewer patients requiring TNFi therapy. The median (IQR) and mean (SD) Ca-CRP was 8.8 (4.6-14.8) and 11.72 (10.52), respectively. On multiple linear regression, erosions, sacroiliitis and CCI were most significantly associated with ca-CRP [(F = 77.6, p < 0.001), 72% (R-square)]. Conclusions Elevated CRP is associated with radiographic damage, disease more resistant to treatment and also having higher number of significant comorbidities. Raised CRP can help stratify patients with a more severe PsA phenotype.