Validity and Reliability of the Dutch Adaptation of the Psoriatic Arthritis Quality of Life (PsAQoL) Questionnaire

Freke Wink,Suzanne Arends,Stephen P Mckenna,Pieternella M Houtman,Anneke Spoorenberg,Elisabeth Brouwer

doi:10.1371/journal.pone.0055912

Abstract

ObjectiveThe Psoriatic Arthritis Quality of Life (PsAQoL) questionnaire is a disease- specific instrument developed to measure quality of life (QoL) in patients with psoriatic arthritis (PsA). The aim of this study was to translate the measure into Dutch and to determine its psychometric properties.MethodTranslation of the original English PsAQoL into Dutch was performed by bilingual and lay panel. Ten field-test interviews with PsA patients were performed to assess face and content validity. In total, 211 PsA patients were included in a test-retest postal survey to investigate the reliability and construct validity of the Dutch adaptation of the PsAQoL. The PsAQoL, Health Assessment Questionnaire (HAQ) and Skindex-17 were administered on two different occasions approximately two weeks apart.ResultsThe Dutch version of the PsAQoL was found to be relevant, understandable and easy to complete in only a few minutes. It correlated as expected with the HAQ (Spearman’s ρ = 0.72) and the 2 subscales of the Skindex-17 (ρ = 0.40 for the psychosocial and ρ = 0.46 for the symptom scale). Furthermore, the measure had good internal consistency (Cronbach’s α = 0.92) and test-retest reliability (ρ = 0.89). The PsAQoL was able to define groups of patients based on self-reported general health status, self-reported severity of PsA and flare of arthritis. Duration of PsA did not influence PsAQoL scores.ConclusionsThe Dutch version of the PsAQoL is a valid and reliable questionnaire suitable for use in clinical or research settings to asses PsA-specific QoL.

Highlights

The Dutch version of the Psoriatic Arthritis Quality of Life (PsAQoL) was found to be relevant, understandable and easy to complete in only a few minutes
The PsAQoL was able to define groups of patients based on self-reported general health status, self-reported severity of Psoriatic arthritis (PsA) and flare of arthritis
Psoriatic arthritis (PsA) is an inflammatory arthritis associated with psoriasis

Summary

Introduction

Psoriatic arthritis (PsA) is an inflammatory arthritis associated with psoriasis. PsA is characterized by synovitis, dactylitis, enthesitis and spondylitis. In approximately 15–20% of patients, arthritis is the first presenting symptom (PsA sine psoriasis) [1,2]. Therapy in patients with PsA focuses on both the improvement of symptoms and functioning and on improvement of quality of life (QoL). The most commonly operationalised definition of QoL in health outcomes research is the needs-based model [3]. This model sees QoL as the extent to which a patient is able to meet his or her needs. Symptoms and activity limitations are only important where they prevent needs from being met. QoL is good when most needs are met and poor when disease and/or its treatment prevents need fulfilment. QoL is a unidimensional construct, as has been shown by the development of several disease-specific QoL measures [4,5,6,7,8]

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