Chronic kidney disease in patients with psoriatic arthritis: a cohort study.

Objectives: Chronic kidney disease (CKD) is a comorbidity in psoriatic arthritis (PsA). We aimed to define the prevalence of CKD in patients with PsA, describe their long-term renal outcomes and identify risk factors for CKD development.

Methods: We included patients with PsA followed by our prospective observational cohort. We defined CKD as an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² for at least 3 months. We characterised long-term renal outcomes of CKD cases identified following clinic entry. We used time-dependent Cox regression models to identify factors associated with CKD development.

Results: Of 1336 patients included in the study, 123 (9.2%) had CKD. Of these, 25 (20.3%) were observed to have CKD at clinic entry and 98 (79.7%) developed CKD during follow-up at a median (IQR) of 8.2 (2.8-14.0) years from baseline. Doubling of baseline creatinine was observed in 18 of 98 (18.3%) new patients with CKD. 49 (50%) patients developed a sustained ≥40% reduction in baseline eGFR. Two patients developed eGFR <15 mL/min/1.73 m². In the multivariate Cox regression model adjusted for age at study entry, sex and baseline eGFR, factors independently associated with the development of CKD included diabetes mellitus (HR 2.58, p<0.001), kidney stones (HR 2.14, p=0.01), radiographic damaged joint count (HR 1.02, p=0.02), uric acid (HR 1.21, p<0.001; 50-unit increase), daily use of non-steroidal anti-inflammatory drugs (NSAIDs) (HR 1.77, p=0.02) and methotrexate use (HR 0.51, p=0.01).

Conclusion: CKD is not infrequent in PsA. Its development is associated with related comorbidities, joint damage and NSAID use. Methotrexate seems to be protective.