Carolyn McMillan, Clare Bradley, Salman Razvi and Jolanta Weaver (2008)
Evaluation of new measures of the impact of hypothyroidism on quality of life and symptoms: the ThyDQoL and ThySRQ. Value in Health, 11 (2).
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This paper reports the psychometric properties of two new condition-specific questionnaires: 1) the 18-item ThyDQoL individualised measure of perceived impact of hypothyroidism on quality of life (QoL), and 2) the 15-item ThySRQ, in which patients rate symptom bother.
Methods: 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.
Results: 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 (AWI-18), for which the sample mean, -3.11 (2.2), indicated considerable negative impact of hypothyroidism on QoL (maximum possible range 9 to +3). There is good preliminary evidence to justify shortening the ThyDQoLto 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.
Conclusions: 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.
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