Day zero parathyroid hormone levels predict cure after parathyroidectomy

Objective:
To evaluate the predictive value of day zero post-operative parathyroid hormone (PTH) levels in determining cure for primary hyperparathyroidism (pHPT) following parathyroidectomy.

Methods:
This multicentre, retrospective diagnostic accuracy study utilized data from a single surgeon. Patients who underwent parathyroidectomy for pHPT were included, with exclusions for secondary or tertiary causes and incomplete follow-up. Day zero post-operative PTH levels were the key predictor variable, while cure at 6 months, defined by normocalcaemia, was the outcome. Diagnostic parameters including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated for an optimal PTH cut-off determined using a receiver operating characteristic (ROC) curve and Youden's index.

Results:
Out of 291 patients included, 278 (95.5%) were cured at 6 months. An optimal PTH cut-off of <3 pmol/L was identified, correlating with a true positive rate of 81.3% and a false positive rate of 0%. Patients with day zero PTH <3 pmol/L (77.7% of the cohort) were all cured at six months. The PTH <3 pmol/L cut-off demonstrated a sensitivity of 81.3%, specificity of 100%, PPV of 100%, NPV of 20%, and an accuracy of 82.1%.

Conclusion:
Day zero post-operative PTH level < 3 pmol/L is a reliable predictor of cure for pHPT following parathyroidectomy. A PTH level of <3 pmol/L is an effective cut-off to identify patients who will be cured, potentially reducing the need for prolonged biochemical monitoring.