Validity and reliability of the Persian version of Behcet's disease quality-of-life (BD-QoL) questionnaire: a cross-cultural adaptation.

The Leeds Behcet's disease quality-of-life (BD-QoL) questionnaire is a specific and valid measure which is applied in English-speaking patients. We conducted Persian adaptation of BD-QoL questionnaire. Between June and December 2012, 220 Iranian patients fulfilling International Study Group criteria for the diagnosis of BD attending the rheumatology clinics at Tehran University of Medical Sciences were enrolled. Bilingual translators undertook the forward translation and cross-cultural adaptation of the BD-QoL questionnaire. Back-translation was conducted, and this version was sent to the designer of the questionnaire and revised accordingly. SF-36 health survey, Iranian Behcet's disease dynamic activity measure (IBDDAM), and Behcet's Disease Current Activity Form (BDCAF) were other administered measures. The Varimax rotation method with Kaiser normalization defined 5 factors with eigenvalues greater than 1.0. Studied cases were comprised of 118 males (53.6 %) and 102 females (46.4 %). Mean age of the patients was 38.3 +/- 11.3 years (range 16-73). The mean BD-QoL score was 10.3 +/- 8.8. Test-retest reliability was high, and two time points were significantly correlated (Spearman's correlation coefficient of 0.75-0.84). Cronbach's alpha coefficient of 0.949 demonstrated the excellent internal consistency. These factors cumulatively explained 58.74 % of total variance. The ratio of first to second eigenvalue was 7.08, which underlined the undimensionality. The results revealed adapted BD-QoL scores had significant correlation with IBDDAM (correlation coefficient = 0.19, P value = 0.005) and BDCAF (correlation coefficient = 0.21, P value = 0.002). Conversely, no significant correlation between BD-QoL and SF-36 results was detected (P value = 0.078). The Persian version of BD-QoL was shown to be unidimensional, highly reliable, and adequate construct validity.