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

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.

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.

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).

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.

QoL assessment is important for holistic management of TED patients.