Nail involvement as a predictor of concomitant psoriatic arthritis in patients with psoriasis

Patients with psoriatic arthritis (PsA) suffer from increased burden of disease and impairments in quality of life. Early detection and treatment of PsA could contribute to the prevention of clinical and radiological progression.

To analyse the predictive value of clinical and patient-reported outcomes for concomitant PsA in a population-based cohort of patients with psoriasis.

We performed a retrospective analysis of data from three independent national cross-sectional studies on health care in psoriasis and PsA, conducted in Germany in the years 2005, 2007 and 2008. Patients with psoriasis were included in the study by dermatologists (n = 3520) and via the German patient advocacy group for psoriasis (n = 2449). In all studies, psoriasis history, clinical findings, PsA, nail involvement, health care and patient-reported outcomes were collected with standardized questionnaires.

In the regression model on 4146 patients the strongest predictors for concomitant PsA were nail involvement [odds ratio (OR) 2·93, 95% confidence interval (CI) 2·51-3·42, P < 0·001] and inpatient hospital treatment (OR 1·63, 95% CI 1·38-1·93, P < 0·001). By contrast, scalp involvement was not a significant predictor.

Patients with psoriasis seen by dermatologists and those in patient advocacy groups show clinical indicators of PsA, the most predictive being nail disease. In practice, a comprehensive assessment of clinical findings associated with PsA is needed.