Psychometric evaluation of the hypoparathyroidism symptom diary.

To conduct an initial psychometric evaluation of the reliability and validity of the Hypoparathyroidism Symptom Diary (HPT-SD).Data were collected during a cross-sectional, observational study. Participants with self-reported hypoparathyroidism (HPT) completed the HPT-SD, the Functional Assessment in Cancer Therapy-Cognitive Function (FACT-Cog), the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue), and the Hospital Anxiety and Depression Scale (HADS) measures. Item- and scale-level internal consistency reliability, known-groups validity, and construct validity were evaluated. Subscales were identified and preliminary scoring algorithms were developed.

The study included 52 participants (mean age, 51 years). Overall, the measurement properties of the HPT-SD were very good. Item-level response frequency distributions showed evidence of possible floor effects for four muscle-related symptom items. Inter-item correlations revealed a pattern of relationships among symptom items (r=0.3-0.8) and among impact items (r=0.5-0.7) and provided evidence for two HPT-SD subscales: Symptoms and Impacts. Construct validity correlations supported a priori convergent validity hypotheses (|r|≥0.4) between HPT-SD subscales and the FACT-Cog, FACIT-Fatigue, and HADS. Mean HPT-SD Symptom and Impact scores were in the expected direction and significantly different between subgroups of patients with high and low HPT disease severity.

Results indicate that the HPT-SD is an appropriate measure of HPT-related symptoms and impacts. Floor effects may be attributed to the observational study design: participants manage symptoms with calcium and active vitamin D supplements prior to an escalation in severity. Future studies should assess the HPT-SD measurement properties using longitudinal study designs.