Psychometric properties of the thyroid-specific quality of life questionnaire ThyPRO in Singaporean patients with Graves’ disease

Abstract

Background Graves’ disease is the most common cause of hyperthyroidism. It results in accelerated tissue metabolism with multi-organ involvement ranging from cardiovascular to neuropsychological function. This results in a negative impact on the quality of life (QOL) of the individual patient. We aim to evaluate the psychometric properties of ThyPRO, a Thyroid-related Patient Reported Outcome questionnaire, and validate its use in our multi-ethnic Asian patients with Graves’ hyperthyroidism. Methods Forty-seven consecutive Graves’ hyperthyroidism patients answered the ThyPRO questionnaire at baseline and at 4 months after treatment initiation. Data were recorded for thyroid related symptoms and signs, thyroid function tests and thyroid volume. We analyzed the internal consistency using Cronbach’s alpha, construct validity by evaluating relationship between clinical variables and ThyPRO scales, ceiling and floor effects, and responsiveness of ThyPRO to treatment based on Cohen’s effect size. Results Correlations between individual scale scores and free thyroxine concentrations were moderate and statistically significant: 0.21–0.64 (p < 0.05). There was high internal consistency between the items in this instrument, Cronbach’s alpha > 0.7 for all scales. ThyPRO was responsive to the changes in QOL after treatment (Effect Size: 0.20–0.77) in 9 of the 14 scales including the hyperthyroid symptoms and psychosocial scales (Tiredness, Cognitive complaints, Anxiety, Emotional susceptibility, Impact on Social, Daily and Sex life). Conclusion This study provides evidence that ThyPRO has satisfactory measurement properties in hyperthyroid Graves’ disease patients in Singapore population with the potential to complement clinical care.