The Hypoparathyroidism Symptom Diary (HypoPT-SD) was developed for the daily assessment of key symptoms and impact of HypoPT as reported by patients with chronic HypoPT and includes 13-items: a 7-item Symptom subscale, 4-item Impact subscale, and single-item anxiety and depression scores. The current analysis was undertaken to confirm test-retest reliability and construct validity of HypoPT SD Symptom subscale scores using data collected during two open-label, single-arm studies of patients with chronic HypoPT treated with recombinant human parathyroid hormone (1-84) (52-week study: NCT03364738; 36-month study: NCT02910466). Test-retest reliability was determined by computing intraclass correlation coefficients (ICC) using data from two test administrations. Validity was evaluated by performing cross-sectional correlational analyses between HypoPT-SD Symptom subscale and other conceptually linked patient-reported outcome (PRO) tools. ANOVA was used to compare HypoPT-SD scores across severity groups defined by existing PRO tools to confirm the known-groups validity of the HypoPT-SD Symptom subscale. The psychometric study population included 22 patients from the 52-week study (81% women; mean ± SD age, 50±11.4 years; mean ± SD duration of HypoPT, 10.3±10.2 years) and 38 patients from the 36-month study (79% women; aged 52±12.4 years; duration of HypoPT, 18.9±12.0 years). In both studies, symptom-related item scores were generally low (eg, less severe), showed limited variability at baseline and end of treatment, most inter-item correlations exceeded 0.50, and internal consistency reliability was satisfactory (>0.82). ICCs were 0.67 (n=22) and 0.82 (n=26) for all patients in the 52-week and 36-month studies, respectively, and 0.92 (n=10) for stable patients (based on the Patient Global Impression–Severity [PGI S]) in the 52-week study and corroborated the test-retest reliability of HypoPT SD Symptom subscale. Patterns of correlations between HypoPT-SD Symptom scores and validated PRO tools (FACT-Cog [baseline], FACIT-F total score, RAND-36 physical health composite, PGI-S, and EuroQoL-visual analog scale [baseline]) were moderate to strong and supported convergent validity expectations. Mean HypoPT SD Symptom scores differed significantly across severity groups defined by PGI-S (52-week study) and RAND-36 general health perceptions (36-month study), demonstrating the known-groups validity of HypoPT SD Symptom scores. Limitations include differences in HypoPT SD recall periods (24 hours vs 7 days) in the two studies and lack of severe HypoPT symptoms in patients at baseline, which restricted the range of possible change in scores. These results provide confirmation of the reliability and validity of the disease-specific HypoPT-SD and lay the psychometric groundwork for use of HypoPT-SD in future clinical trials of adults with HypoPT.
