CRP at diagnosis in psoriatic arthritis: what it means and associations with long-term outcomes

OBJECTIVE: The role of C-reactive protein (CRP) in Psoriatic Arthritis (PsA) as a diagnostic and prognostic marker is debated. We compared clinical and epidemiological features, as well as long-term outcomes, between patients with "elevated" (>0.5 mg/dL) and patients with "normal" (≤0.5 mg/dL) CRP at diagnosis. METHODS: In this real-world study, we analyzed data from 609 PsA patients categorized by their CRP at diagnosis. Demographics, clinical characteristics, comorbidities, and long-term outcomes were compared. The statistically significant variables in the univariate analyses were used to build two multivariable logistic regression models: i. assessing associations between CRP and features at PsA diagnosis, ii. examining its link with long-term outcomes (including "difficult to manage" and "persistent disease") and characteristics throughout the disease course. RESULTS: Of 609 patients, 132 (21.7%) displayed normal and 477 (78.3%) elevated CRP values at diagnosis. By univariate analysis, elevated CRP was associated with longer disease follow-up, BMI > 25 Kg/m2, enthesitis (at diagnosis and disease course), hypertension, hyperuricemia, new bone formation and "persistent disease". By multivariable analyses, elevated CRP at diagnosis was independently linked with BMI >25 Kg/m2 (OR 1.69, 95% CI 1.05-2.72), enthesitis (OR 2.04, 95% CI 1.24-3.38), hypertension (OR 2.07, 95% CI 1.04-4.11), new bone formation (OR 2.57, 95% CI 1.33-4.94), and "persistent disease" (OR 4.36, 95% CI 2.22-8.59). CONCLUSION: Overall PsA characteristics are comparable, irrespective of the CRP-levels at diagnosis, apart from new bone formation, enthesitis, "persistent disease" and increased cardiometabolic burden which were independently associated with elevated CRP-levels at PsA diagnosis.