Intraoperative parathyroid hormone assay benefits surgery for primary hyperparathyroidism when preoperative localisation is negative or not performed.

Introduction: Parathyroid localisation is now routine before first-time surgery for patients with primary hyperparathyroidism (PHPT). The aim of this study was to investigate the contribution of intraoperative parathyroid hormone (PTH) (ioPTH) in patients in whom localisation was either not undertaken or negative for a tumour.

Methods: This was a retrospective study of patients undergoing first-time parathyroidectomy for PHPT in a regional endocrine centre. Data were collected prospectively (Microsoft Excel) and the all-Wales electronic patient record portal was used to retrieve missing data. Statistical analysis appropriate for nonparametric data was undertaken, with statistical significance reached when <0.05.

Results: Between 1 July 2002 and 31 December 2022, 1,490 patients underwent a first-time parathyroidectomy for PHPT. Of this cohort, 1,133 patients had at least one positive imaging modality; the study group consisted of 343 patients that had negative imaging, and 13 that had no preoperative localisation. Patients with MEN-1 (=26), an incorrect diagnosis (=4), or less than six months follow-up (=6) were excluded. Of the remaining 321, 106 patients underwent surgery without ioPTH (Group A), 215 cases with ioPTH (Group B). In Group B there were more women (170 female/45 male; 79% vs 67 female/37 male; 63% =0.002, chi-squared), lower calcium (median [range] 2.77 [2.63-3.24] mmol/l; vs 2.85 [2.60-4.52] =0.001) and lower PTH (12.0pmol/l [3.4-39.5] vs 14.4 [3.9-97.0] =0.001) and smaller weights of resected tissue (320mg [50-9,000] vs 454 [46-8,280] =0.02) (Student's -test). The rate of multiple gland disease was similar (Group A 29%; Group B 27%). The rate of normocalcaemia at 6 months was significantly higher when ioPTH was used (Group B 202/215; 94% vs Group A 90/106; 85%) (=0.014, chi-square test). The sensitivity and specificity of ioPTH was 98.5% [confidence interval (CI) 96.2-99.6] and 91.2% [80.7-97.0] (positive predictive value 99.9%, CI 93.6-100.0).

Conclusion: Despite milder hyperparathyroidism and smaller tumour weight, the outcome in patients in whom ioPTH was used was superior, with failure rates 2.5-fold higher in the cohort where ioPTH was not utilised. The results of this study demonstrate that ioPTH is a valuable adjunct for the surgeon in cases where localisation has failed or not been undertaken.