Turkish lupusPRO: cross-cultural validation study for lupus

Abstract

LupusPRO is a disease-targeted patient-reported outcome measure that was developed and validated from and among US patients with systemic lupus erythematosus (SLE). We herein report the results of the cross-cultural adaptation and validation study of the Turkish translated version of the LupusPRO. Turkish LupusPRO and the Medical Outcomes Study Short Form (SF-36) (Turkish) were administered to the Turkish lupus patients. Disease activity was ascertained using the physician global assessment (PGA), Safety of Estrogens in Lupus Erythematosus National Assessment-Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI), and flare (defined by LFA-Lupus Foundation of America). Disease damage was assessed with Systemic Lupus International Collaborating Clinics/American College of Rheumatology damage index (SDI). Also, second Turkish LupusPRO tests were given to the patients to be completed within 2-3days and sent back to us. Internal consistency reliability, test-retest reliability, and convergent and criterion validity (against disease activity or health status) were tested. All reported p values are two-tailed. The conceptual framework of the LupusPRO was evaluated using confirmatory factor analysis appropriate for categorical data. One hundred two SLE subjects (94% women) were enrolled. The median (IQR) age and mean disease duration (±SD) were 38.5 (18) years and 60.3 (±56.3) months, respectively. The mean ± SD, SLEDAI, and SDI scores were 3.1 ± 3.7 and 0.52 ± 0.75, respectively. There were 25 patients who had flares at the time of study. Forty-two patients with no change in their health status completed and sent back the second LupusPRO test and were included in the test-retest analysis. Test-retest reliability of LupusPRO domains ranged from 0.87 to 0.97, while internal consistency reliability of the domains ranged from 0.63 to 0.94. Convergent validity with corresponding domains of SF-36 was present. Health-related quality-of-life domains performed well against disease activity measures (PGA, total SLEDAI, LFA flare, and SF-6D-overall health status), establishing its criterion validity. Item-to-factor loadings representing the hypothesized item-to-scale relationships were satisfactory. The model fit for the hypothesized item-to-scale relationships was also satisfactory. The Turkish version of the LupusPRO is valid and appears to perform comparably to the English and Spanish language versions. It can be used as a patient-reported outcome parameter in clinical trials, as well as longitudinal studies for testing responsiveness to change.