The thyroid-related patient-reported outcome measure ThyPRO is currently the most reliable and valid instrument for the measurement of thyroid-related quality of life. The objective of the current study was to translate the original (85 items) and short (39 items) versions of ThyPRO into the Greek language as well as to validate and culturally adapt ThyPRO among the Greek population. Translation of patient-reported outcomes was done according to standard methodology. Following the translation process, the Greek version of ThyPRO (ThyPROgr) was validated in consecutive patients with thyroid diseases who visited the outpatient clinics of the Department of Endocrinology, "Hippokration" General Hospital, Thessaloniki, Greece, between September and December 2016. To test cross-cultural validity, analysis of differential item functioning (DIF) between the original Danish and the new Greek version, using ordinal logistic regression, was applied. Cross-cultural validity of the Greek translation was evaluated for both versions of ThyPRO. The ThyPRO questionnaire was validated in 143 consecutive patients (131 women and 12 men) with thyroid diseases, with a mean age of 62 ± 6 (SD) years. In the 85-item ThyPRO, 17 instances of DIF were detected, most of which were minor, this accounting for the ~ 5% of the variation in scale score. Two instances of DIF among positively worded items were larger, with 8-10% of variance explained. For ThyPRO-39, five minor instances of DIF were found. As judged by the linguistic validation as well as the DIF analyses, ThyPROgr has good cross-cultural validity when compared with the original Danish version. The two versions of ThyPROgr can now be used to assess thyroid-specific quality of life in the Greek population.
Keywords: Patient-reported outcomes; Quality of life; ThyPRO; Thyroid diseases.