INTRODUCTION AND PURPOSE: Use of electronic questionnaires to collect health-related quality-of-life data has evolved as an alternative to paper questionnaires. For the electronic questionnaire to be used interchangeably with the validated paper questionnaire, measurement properties similar to the original must be demonstrated. The aim of the present study was to assess the equivalence between the paper version and the electronic version of the thyroid-related quality-of-life questionnaire ThyPRO.

METHODS: Patients with Graves' hyperthyroidism or autoimmune hypothyroidism in a clinically stable phase were included. The patients were recruited from two endocrine outpatient centers. All patients completed both versions in a randomized test-retest set-up. Scores were compared using intraclass correlation coefficients (ICCs), paired t tests and Bland-Altman plots. Limits of agreement were compared with data from a previous paper-paper test-retest study.

RESULTS: 104 patients were included. ICCs were generally high for the 13 scales, ranging from 0.76 to 0.95. There was a small but significant difference in the scale score between paper and electronic administration for the Cosmetic complaints scale, but no differences were found for any other scale. Bland-Altman plots showed similar limits of agreement compared to the earlier test-retest study of the paper version of ThyPRO.

CONCLUSION: Based on our analyses using ICCs, paired t tests and Bland-Altman plots, we found adequate agreement between the paper and electronic questionnaires. The statistically significant difference in score found in the Cosmetic complaints scale is small and probably clinically insignificant.