Translation, cross-cultural adaptation and validation of the Osteoarthritis Quality of Life (OAQoL) questionnaire for use in Portugal.

Osteoarthritis (OA) is the most prevalent rheumatic disease and is a leading cause of decreased quality of life (QoL). The OA Quality of Life questionnaire (OAQoL) is an OA-specific patient-reported outcome measures. The aim of this study was to translate and validate the original UK English version of the Osteoarthritis Quality of Life (OAQoL) questionnaire into European Portuguese. The translation of the questionnaire was carried out according to a dual panel methodology (bilingual panel followed by lay panel). This was followed by cognitive debriefing interviews (CDIs) with OA patients to assess comprehension and relevance of the translated questionnaire. Finally, a validation survey was conducted to assess its psychometric properties. The Portuguese OAQoL, a comparator scale (the Nottingham Health Profile-NHP) as well as questions relating to demographic and disease information were administered to OA patients. A sub-sample of patients also completed the Portuguese OAQoL two weeks later, to assess test-retest reliability. The internal consistency, construct validity and known group validity (according to perceived OA severity) of the scale was also assessed. Both the bilingual and lay panels consisted of five individuals and no major difficulties relating to the translation process were identified. A total of ten patients with OA participated in the CDIs. The mean time to complete the questionnaire was 5 min. These interviews revealed that the Portuguese version of the OAQoL was clear, relevant and easy to complete. Finally, 53 OA patients (44 females; mean age of 67.6 years) completed the validation survey. Cronbach's alpha coefficient was 0.87, demonstrating high internal consistency. Test-retest reliability, assessed by Spearman's rank correlation coefficient, was 0.86. Moderate correlations were found with the majority of the NHP sections, providing evidence of construct validity. Significant differences in OAQoL scores were found between patients who differed according to their perceived OA severity, providing evidence of known group validity. The Portuguese version of the OAQoL is a valid and reliable questionnaire that can be used to assess QoL in OA, both in clinical practice and for research purposes.