Adaptation and validation of the Bulgarian version of the Systemic Lupus Erythematosus Quality of Life Questionnaire (L-QoL).

OBJECTIVE: Systemic lupus erythematosus (SLE) is a heterogeneous disease with multiple clinical manifestations, which causes a significant deterioration in the quality of life (QoL). The Systemic Lupus Erythematosus Quality of Life Questionnaire (L-QoL) is a lupus-specific measure used to determine the burden of the disease and it applies the need-based model of QoL. Our aim was to produce the first successfully validated foreign language version of the questionnaire. METHODS: The development of the Bulgarian version involved three stages: translation, field testing and psychometric evaluation. Translation was conducted by an expert linguist working with a developer of the original L-QoL, followed by interviews with monolingual lay individuals. Face and content validity of the translation were assessed by cognitive debriefing interviews with Bulgarian SLE patients. Finally, the L-QoL was validated by administering the questionnaire to a random sample of SLE patients on two occasions, 2 weeks apart to evaluate its reliability and validity. RESULTS: In the validation survey, the new Bulgarian version demonstrated high internal consistency (the Cronbach's alpha coefficient was 0.92), and test-retest reliability (0.97). Additionally, scores on the L-QoL were correlated with those on the SF-36 sections to determine convergent validity and the strongest correlation was observed between L-QoL scores and the social functioning section of the SF-36. Known group validity was established by testing the ability of the Bulgarian L-QoL to distinguish between subgroups of patients from the study pool. CONCLUSIONS: The demonstrated excellent psychometric properties ensure that the Bulgarian L-QoL accurately captures the impact of SLE on the quality of life. Key points • The Bulgarian version of the L-QoL is a valid and reliable measure of QoL in lupus patients. • The Bulgarian version of the L-QoL can be used as an outcome measure in research, clinical trials and routine clinical practice.

Adaptation and validation of the Rheumatoid Arthritis Quality of Life (RAQoL) questionnaire for use in Bulgaria.

Rheumatoid arthritis (RA) is a chronic disease with an enormous impact on patients' quality of life. The Rheumatoid Arthritis Quality of Life (RAQoL) questionnaire is a disease-specific measure of QoL for individuals with rheumatoid arthritis. Our aim was to adapt and validate the RAQoL for use in Bulgaria. The development of a new language version of the RAQoL consisted of three stages: translation, field testing and psychometric evaluation. The dual-panel methodology, requiring two independent panels of Bulgarian speakers, was applied to translate the UK English version of the RAQoL into Bulgarian. Face and content validity of the translated questionnaire were assessed through cognitive debriefing interviews. Lastly, the RAQoL was administered on two occasions to a random sample of RA patients to evaluate reliability and validity. At the first occasion, the SF-36 was also administered for use as a comparator scale. The RAQoL was successfully adapted into Bulgarian and considered easy to understand, acceptable and comprehensive by RA patients. A psychometric study demonstrated that the new language version has excellent internal consistency (Cronbach's alpha coefficients = 0.93 and 0.94) and test-retest reliability (a Spearman's rank correlation coefficient = 0.97). Convergent validity was established by correlating scores on the RAQoL with a comparator measure, the SF-36. A strong correlation between RAQoL scores and the physical functioning section of the SF-36 was observed. Known group validity was established by the ability of the measure to distinguish between subgroups of patients, who differed according to their perceived general health, disease severity (p < 0.001) and whether they were experiencing a flare-up (p < 0.01). The new language version is recommended for use in future research studies, clinical trials and routine practice with Bulgarian RA patients.