Translation and validation of the greek Psoriatic Arthritis Quality of Life Scale

Abstract

Psoriatic arthritis (PsA) is a chronic inflammatory disease that has a significant impact on patients' quality of life (QoL). The Psoriatic Arthritis Quality of Life (PsAQoL) Scale was developed in the UK to be specific to PsA patients and adopts the needs-based model of QoL. As a disease-specific measure, the PsAQoL is superior to generic measures of QoL in terms of relevance and sensitivity. The measure, which has been adapted into 50 languages, has not previously been available for use with Greek PsA patients. The aim of the study was to produce a Greek version of the PsAQoL that was suitable for native Greek speakers and that had comparable psychometric properties to the original UK version. The adaptation of the Greek PsAQoL consisted of three stages; translation, assessment of face and content validity and analysis of its psychometric properties. The translation stage adopted the dual panel methodology -a bilingual panel followed by a lay panel- to ensure conceptual equivalence of the scale to the original version. Cognitive debriefing interviews were conducted to determine the applicability and relevance of the adapted scale to patients. Finally, a postal validation survey was conducted to assess the psychometric properties of the draft measure, using the Nottingham Health Profile (NHP) as a comparator instrument. Non-parametric statistical analyses were performed to establish the reliability and construct validity of the PsAQoL. The translation panels produced a language version that sounded natural to native Greek speakers. Interviews revealed that patients found the measure comprehensible and appropriate. Only minor grammatical changes were made to the measure following these interviews. The Greek PsAQoL demonstrated good internal consistency (Cronbach's α=0.88) and excellent test-retest reliability (r=0.98). As expected, the measure correlated moderately highly with the Physical Mobility and Pain sections of the NHP and correlated moderately with other sections, indicating convergent validity. Known group validity was established by the ability of the measure to distinguish between patients who differed according to their perceived general health and disease severity. No significant differences in PsAQoL scores were observed between males and females or older and younger patients. The Greek PsAQoL was well-received by patients and demonstrated sound psychometric properties. It forms part of a growing body of disease-specific measures that are available in Greece. It is recommended for use in routine clinical practice, international clinical trials and research studies as a valid and reliable measure of QoL in PsA patients.