Background Generic health status instruments such as the Health Assessment Questionnaire (HAQ), the Arthritis Impact Measurement Scale (AIMS) and the 36-item Short Form Health Survey (SF-36) are commonly used to attempt to evaluate the total impact of psoriatic arthritis (PsA). However, these questionnaires predominantly focus on impairment and disability rather than quality of life (QoL). McKenna et al. have developed and validated the Psoriatic Arthritis Quality of Life (PsAQoL) questionnaire. This is a disease specific instrument developed to measure QoL in patients with PsA (1).
Objectives To assess the construct validity and test-retest reliability of the Dutch version of the PsAQoL.
Methods In total 209 consecutive outpatients were available for a test-retest postal survey to investigate the construct validity and test-retest reliability of the Dutch version of the PsAQoL. All patients fulfilled the Classification criteria of Psoriatic Arthritis (CASPAR) for PsA. The PsAQoL, Health Assessment Questionnaire (HAQ) and Skindex-17 were administered on two different occasions approximately two weeks apart. Construct validity was examined by calculating Spearman’s correlation coefficients between the PsAQoL score and the HAQ and Skindex-17 scores. Test-retest reliability was investigated by calculating the intraclass correlation coefficient (ICC) between the first and second assessments of the PsAQoL. Additionally, Bland-Altman analysis was performed
Results Mean age of the 183 (87.6%) responding PsA patients was 55.4 years (SD± 12.5), median disease duration was 5.5 years (range 0.3-45) and 55% were male. The Dutch version of the PsAQoL showed good association to the HAQ (ρ=0.722) and moderate association to the Skindex-17 (ρ=0.464), indicating acceptable construct validity. Furthermore, good internal consistency (Cronbach’s α=0.920) and test-retest reliability (ICC=0.889) of the PsAQoL were found. Bland-Altman analysis showed no systemic bias between the first and second assessments of the PsAQoL. The limits of agreement (LOA) of the PsAQoL were found between -5.3 and 5.1 out of a total of 20, indicating good agreement.
Conclusions The Dutch version of the PsAQoL is a valid and reliable questionnaire to use in clinical or research settings to asses disease-related QoL in patients with PsA.
McKenna SP, Doward LC, Whalley D, et al. Development of the PsAQoL: a quality of life instrument specific to psoriatic arthritis. Ann Rheum Dis 2004;63:162-9.
Disclosure of Interest None Declared
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