Objectives: To compare the Psoriatic Arthritis Quality of Life (PsAQoL) instrument, the Health Assessment Questionnaire (HAQ) as a measure of functional status, and the generic health status (utility) measure the EuroQoL (EQ-5D) in terms of ability to assess disease severity in psoriatic arthritis (PsA).
Methods: The differences between known groups and correlations of the PsAQoL, the HAQ and the EQ-5D with clinical measures were analysed in a sample of 183 PsA patients.
Results: Different severities of PsA determined by known groups were distinguished well by all three questionnaires; more severe disease was associated with significantly worse values of the instruments. The correlations revealed a strong relationship between each of the measures, and with the patients' pain on the visual analogue scale (VAS), the patient global VAS, and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and a weak relationship with the disease duration and the Psoriasis Area Severity Index (PASI). The PsAQoL also correlated strongly with the 28-joint Disease Activity Score (DAS28).
Conclusions: The PsAQoL, the HAQ, and the EQ-5D are able to distinguish well across levels of PsA severity.