This article reports the psychometric properties of two new condition-specific questionnaires: 1) the 18-item Underactive Thyroid-Dependent Quality of Life Questionnaire (ThyDQoL) individualized measure of perceived impact of hypothyroidism on quality of life (QoL); and 2) the 15-item Underactive Thyroid Symptom Rating Questionnaire (ThySRQ), in which patients rate symptom bother.
A cross-sectional survey was conducted of 110 adults with overt and subclinical hypothyroidism, 103 treated with thyroxine. Patients, the majority of whom (81%) were women, were recruited from primary care (57%) and from hospital clinics (43%). The mean age of patients was 55.1 (SD 14.3) years. Respondents rated personally applicable ThyDQoL life domains for importance and impact of hypothyroidism, and ThySRQ symptom bother.
Completion rates were high (>98%). All 18 ThyDQoL domains were rated as negatively impacted by hypothyroidism and important for QoL. The ThyDQoL had high internal consistency reliability (Cronbach's alpha = 0.949 [N = 97]), factor analysis indicated that applicable domains could be combined into an overall Average Weighted Impact score, for which the sample mean, −3.11 (2.2), showed considerable negative impact of hypothyroidism on QoL (maximum possible range −9 to +3). There is good preliminary evidence to justify shortening the ThyDQoL to 14 domain-specific items. For the ThySRQ Cronbach's alpha was 0.808 (N = 95). Highest symptom bother ratings were for hair problems, weight gain, depression, cold, and tiredness.
Both the ThyDQoL and ThySRQ are highly acceptable to patients with hypothyroidism and have good internal consistency reliability. Their sensitivity to change now needs to be evaluated in clinical trials.