A randomised study on a new cost-effective algorithm of quick intraoperative intact parathyroid hormone assay in secondary hyperparathyroidism

The use of intraoperative intact parathyroid hormone (iPTH) assay in secondary renal hyperparathyroidism (SHP) has been limited by the relatively low cost effectiveness of the assay in improving the success rate for primary bilateral neck exploration. The study aimed at determining, in a prospective, randomised trial, the cost effectiveness and impact of the routine employment of a “six-sample” versus “two-sample” algorithm of the intraoperative iPTH assay during surgery for SHP on intraoperative decision making and surgical success rate.

One hundred and two consecutive patients with severe SHP and qualified for subtotal parathyroidectomy were randomly allocated to two equal-sized groups: group A, in which the intraoperative iPTH serum level was determined in six consecutive samples: preoperative, pre-excision, 5, 10, 20 and 60 min, and group B, in which the intraoperative iPTH serum level was determined twice only: preoperatively and 10 min. The STAT intraoperative intact-PTH immunoassay was employed. In group B, in patients with serum iPTH decrease lower than 60% of the baseline at 10 min, an additional measurement was performed at 20-min post-excision. If a decrease of 80% or more of the baseline was not obtained, the exploration was extended in search of remaining hyperfunctioning parathyroid tissue.

The surgical success rate was 96.1% and 98.0% (in group A and B, respectively). The impact of the intraoperative iPTH assay on surgical decision making was demonstrated in 13.7% and 15.7% (in group A and B, respectively). The assay was helpful in identifying patients with supranumerary hyperfunctioning parathyroid tissue (5.9% vs 7.8% in group A and B, respectively), patients with fewer than four parathyroid glands (3.9% vs 5.9% in group A and B, respectively) and patients with remaining hyperfunctioning parathyroid tissue suspected to be located within the mediastinum in cases of negative bilateral neck exploration who benefit from transcervical thymectomy. The diagnostic accuracy of the intraoperative iPTH assay was 100% in both groups. The accuracy of two-sample algorithm increased from 96% to 100% if an additional serum iPTH determination was performed in borderline cases with an iPTH drop lower than 60% of the baseline at 10 min. The cost-effectiveness analysis showed significant savings in group B, equal to €87.6 per patient, with the unchanged diagnostic accuracy of the two-sample algorithm.

The intraoperative iPTH assay in patients operated on for secondary hyperparathyroidism offers support in surgical decision making in the majority of patients, allowing for correct identification of patients with supranumerary ectopic hyperfunctioning parathyroid glands, and in patients with fewer than four parathyroid glands. It also correctly identifies patients who do not benefit from blind thymectomy. The two-sample algorithm, extended to include three determinations in selected cases, has the same 100% diagnostic accuracy as the six-sample algorithm, the former being a much more cost-effective procedure.