Endocrine Abstracts

Background: Since 2017, we have used IOPTH during surgery for all patients with PHPT and collected pre-incision (S1), pre-excision (S2), and 20 minutes post-excision (S3) samples. >50% drop in S3 from S1 or S2 predicts cure. We use second-generation PTH (intact) measurement by the Abbott immunoassay analyzer.

Patients and methods: We reviewed biochemical, histological, surgical, and imaging details of patients who had IOPTH from 2017-2024. We analysed the impact of IOPTH on surgical outcomes and its positive and negative predictive values. We mathematically estimated 10- and 15-minute post-excision PTH and correlated the presumed outcomes with our findings. We audited 40 patients for the time taken for the availability of results.

Results: n = 251; mean age 65years, 75% females; mean calcium 2.9mmol/l, PTH 25pmol/l. 236 (94%) patients were cured and 15 (6%) were not. 221 (88%) patients had >50% IOPTH drop, of which 217 were cured (true positive) and 4 were not (false positive). 30 (12%) patients had a PTH drop of <50% of which 1 was cured (false negative) and 29/30 were not (true negative). 18/29 patients were cured after further surgery, attributable to IOPTH use, while 1 had unnecessary dissection. The overall PPV was 98% and NPV 96.7%. With the use of a 10-minute sample, 28 and with a 15-minute sample 7 more false negative results would have been achieved. The per-patient cost is £10 as compared to around £400 with point-of-care testing. Mean availability time for IOPTH result was 35 minutes.

Conclusions: Although NICE does not recommend routine IOPTH for initial surgery, our experience shows it predicts surgical outcomes, improves cure rates, and limits dissection. Collecting samples at 20-minutes (rather than using Miami criteria) and using laboratory-based analyzer has replicated the best-reported success rates, keeping the expense at a negligible level at the cost of delayed results (35 minutes).