Development and Validation of the Singapore Thyroid Eye Disease Quality of Life Questionnaire.

Purpose: Current instruments to assess thyroid eye disease (TED) quality of life (QoL) were not developed using modern psychometric theory and may not be applicable to Asian populations. Therefore, we developed a psychometrically robust questionnaire, the Singapore Thyroid Eye Disease Quality of Life questionnaire (STED-QoL), for assessing QoL in Asian patients. Methods: This cross-sectional study was conducted at the Singapore National Eye Centre between 2012 and 2015. In Phase 1, content for the questionnaire was developed using qualitative methods. A total of 20 patients participated in three different focus groups. Thematic analysis was conducted to identify relevant themes from which 12 items, rated on a 5-point Likert-type scale, were generated. In Phase 2, the pilot instrument was administered to 59 TED patients and psychometric assessment of the STED-QoL was conducted using Rasch analysis. Results: After collapsing categories from five to four and deleting two misfitting items, we generated a 10-item STED-QoL befitting the Rasch model. The scale showed good criterion validity, with scores decreasing as severity of TED worsened: mild (1.78 logits), moderate (0.27 logits), and severe (0.92 logits). A 'Psychosocial' subscale also had adequate psychometric properties and psychosocial scores were significantly worse in those who underwent surgery for TED compared to those who had not (0.41 vs. 1.82 logits, P = 0.021). Conclusions: The STED-QoL is a robust 10-item questionnaire specifically developed to measure the impact of TED on QoL and psychosocial well-being in an Asian population.