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

The role of CRP in 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.

In this real-world study, we analysed 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 and (ii) examining its link with long-term outcomes (including 'difficult to manage' and 'persistent disease') and characteristics throughout the disease course.

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 of >25 kg/m2, enthesitis (at diagnosis and during the disease course), hypertension, hyperuricaemia, new bone formation, and 'persistent disease'. By multivariable analyses, elevated CRP at diagnosis was independently linked with BMI of >25 kg/m2 [odds ratio (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).

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.