CLINICAL STUDY Validity and reliability of the novel thyroid-specific quality of life questionnaire, ThyPRO Torquil Watt 1,2 , Laszlo Hegedu ¨s 3 , Mogens Groenvold 2,4 , Jakob Bue Bjorner 2,5 ,A ˚ se Krogh Rasmussen 1 , Steen Joop Bonnema 3 and Ulla Feldt-Rasmussen 1 1 Department of Endocrinology, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark, 2 Institute of Public Health, University of Copenhagen, DK-1014 Copenhagen, Denmark, 3 Department of Endocrinology and Metabolism, Odense University Hospital, Odense, Denmark, 4 Department of Palliative Medicine, Bispebjerg Hospital, Copenhagen, Denmark and 5 National Research Centre for the Working Environment, Copenhagen, Denmark (Correspondence should be addressed to T Watt at Department of Endocrinology, Copenhagen University Hospital Rigshospitalet; Email: t.watt@rh.dk) Abstract Background: Appropriate scale validity and internal consistency reliability have recently been documented for the new thyroid-specific quality of life (QoL) patient-reported outcome (PRO) measure for benign thyroid disorders, the ThyPRO. However, before clinical use, clinical validityand test–retest reliability should be evaluated. Aim: To investigate clinical (‘known-groups’) validity and test–retest reliability of the Danish version of the ThyPRO. Methods: For each of the 13 ThyPRO scales, we defined groups expected to have high versus low scores (‘known-groups’). The clinical validity (known-groups validity) was evaluated by whether the ThyPRO scales could detect expected differences in a cross-sectional study of 907 thyroid patients. Test–retest reliability was evaluated by intra-class correlations of two responses to the ThyPRO 2 weeks apart in a subsample of 87 stable patients. Results: On all 13 ThyPRO scales, we found substantial and significant differences between the groups expected to have high versus low scores. Test–retest reliability was above 0.70 (range 0.77–0.89) for all scales, which is usually considered necessary for comparisons among patient groups, but below 0.90, which is the usual threshold for use in individual patients. Conclusion: We found support for the clinical validity of the new thyroid-specific QoL questionnaire, ThyPRO, and evidence of good test–retest reliability. The questionnaire is nowready for use in clinical studies of patients with thyroid diseases. European Journal of Endocrinology 162 161–167 Introduction Measurements applying standardized self-reports to capture the impact of health on patients’ lives are termed health-related quality of life (HRQL) measure- ments (1). They usually conceptualize HRQL as a multidimensional concept encompassing various aspects of physical, mental, and social functioning and well-being. To an increasing extent, the broader, but also more neutral term ‘patient-reported outcomes (PROs)’ is replacing HRQL. Today, PROs or HRQL measurements are recognized as inevitable and important outcomes in high quality clinical studies. Further, they can provide important documentation for evidence-based patient information and may even be implemented in clinical management of the individual patient, as has been done within, e.g. oncology (2), where randomized trials have documented significant improvement of patient–clinician interaction, without prolonging consultations, and impact on patient management (3). HRQL measurements may be either generic, i.e. applicable to any patient group regardless of diagnosis, or specific, i.e. targeted to a specific disease group. Specific HRQL measurements are usually more sensitive than generic, which on the other hand have the advantage of allowing comparisons across dissimilar populations. Some questionnaires have been developed for specific thyroid diseases (4–12). However, a thoroughly valid- ated questionnaire only exists for thyroid-associated ophthalmopathy (TAO) patients (5–7). Another TAO questionnaire has been developed, but has not been validated (8). One questionnaire for patients with hyperthyroidism was developed, but has never been validated (4). Three questionnaires for hypothyroid patients have been developed (9–12), but studies European Journal of Endocrinology (2010) 162 161–167 ISSN 0804-4643 q 2010 European Society of Endocrinology DOI: 10.1530/EJE-09-0521 Online version via www.eje-online.org Downloaded from Bioscientifica.com at 04/25/2020 07:23:27PM via free access