The Romanian version of the thyroid-related patient-reported outcomes thypro and thypro-39. Translation and assessment of reliability and cross-cultural validity

Background. ThyPRO is a recently developed thyroid-specific quality of life (QoL) questionnaire applicable to patients with benign thyroid disorders(BTD). The aim of the present study was to translate ThyPRO and ThyPRO-39 into Romanian, and to evaluate reliability and cross-cultural validity. Methods. Standard methodology for translation and linguistic validation of patient-reported outcomes (PRO) was applied. The questionnaire was completed by 130 patients with benign thyroid diseases seen at Department of Endocrinology in the Emergency County Hospital, Tîrgu Mureș, Romania, between October 2015 and March 2016. Internal reliability of the Romanian version of the ThyPRO (ThyPROro) scales was assessed for multi-item scales using Cronbach’s alpha coefficient. An efficient method for testing cross-cultural validity is analysis of differential item functioning (DIF). Uniform DIF between the Romanian and the original Danish sample was investigated using ordinal logistic regression. The translation process proceeded without difficulties, and any disagreements were revised by one of the developers and the language coordinator. Results. Internal reliability for ThyPRO was satisfactory. Cronbach`s alpha coefficients for the 13 scales ranged from 0.78 to 0.93 for the ThyPROro and 0.78 to 0.87 for the ThyPROro-39. In the 85-item ThyPRO, nine instances of DIF were found. Most were minor, explaining <3% of the variation in scale score, but DIF in positively worded items were larger, with explained variance (R2’s) around 10-15%. Conclusion. The ThyPROro questionnaire is ready for assessment of health-related quality of life in Romanian patients with benign thyroid diseases.