Longitudinal Performance of the Psoriasis Epidemiology Screening Tool (PEST) in Canada and Latin America: Results from the Prospective, Observational, 5-Year PURE Registry

Introduction

The Psoriasis Epidemiology Screening Tool (PEST) is a 5-item questionnaire designed to identify patients with psoriasis who have co-existing psoriatic arthritis (PsA). This analysis investigated the longitudinal performance of the PEST questionnaire in the prospective, observational PURE registry.

Methods

The PURE registry included 2132 patients with psoriasis who completed the PEST at baseline, 3 and 6 months then every 6 months for 5 years. Baseline diagnostic performance was assessed using existing PsA diagnoses as the reference standard. PEST positivity changes over time were assessed, and regression models determined factors linked to baseline PEST status and conversion from negative to positive. Cronbach’s alpha assessed internal consistency, while exploratory factor analysis evaluated changes in individual PEST questions over time.

Results

At baseline, 906 patients (42.5%) were PEST positive and 373 (17.5%) had PsA, for a diagnostic sensitivity of 89% and a negative predictive value of 97%. Overall, the proportion of patients who became PEST positive increased from 42.5% at baseline to 63.9% at 5 years, rising from 89.0% to 95.8% and 32.6% to 57.2% respectively in those who were PEST positive or negative at baseline. Regression modeling confirmed that increased age (p < 0.0001), weight > 90 kg (p < 0.0001), female sex (p = 0.0107) and prior biologic exposure (p < 0.0001) were related to PEST status at baseline and of which the first three were also related to change from negative to positive during follow-up. Cronbach’s alpha showed high internal consistency of the PEST questionnaire (0.693). Exploratory factor analysis found that responses to questions 1, 2, 4, and 5 increased over time, while question 3 decreased. Eigenvalues revealed consistent dominance of question 1 and two-factor structure in the questionnaire.

Conclusion

The PEST questionnaire is an informative, easy-to-use tool which may be useful to monitor and identify patients with psoriasis who are at risk of PsA over time.