Predictive value of intact parathyroid hormone measurement during surgery for renal hyperparathyroidism

In contrast to that in patients with primary hyperparathyroidism, the value of intraoperative intact parathyroid hormone (iPTH) measurement is still unclear in patients with renal hyperparathyroidism and was, therefore, evaluated in a large cohort of patients.

Intraoperative iPTH measurement was performed in 153 patients with renal hyperparathyroidism (129 with terminal renal failure and 24 with functioning kidney graft). Subtotal and total parathyroidectomy were performed in 123 and 13 patients, respectively, during initial surgery. In patients with recurrent disease (17), the respective hyperfunctioning tissue was removed. Intraoperative blood samples were obtained by puncture of the internal jugular vein before preparation of the parathyroids (PTH₀) and 15 min after parathyroidectomy (PTH₁₅). iPTH was measured with the Elecsys 2010 system. Postoperative iPTH levels (PTH_post) were determined at postoperative days 1 to 3 and at week 2. Patients were arbitrarily divided in four groups according to the postoperative iPTH values: 0–25 pg/ml (group 1), 26–65 pg/ml (group 2), 66–150 pg/ml (group 3) and more than 150 pg/ml (group 4).

The mean PTH₀ value was 869±57 pg/ml, which decreased to 167±15 pg/ml at PTH₁₅. The mean relative PTH₁₅ value was 21.6±1.7%. Postoperatively, iPTH decreased to 42±9 pg/ml. The postoperative iPTH value of the 129 patients with terminal renal failure was 25 pg/ml or less in 99 patients, 26–65 pg/ml in 11 patients, 66–150 pg/ml in eight patients and higher than 150 pg/ml in 11 patients. Two successive criteria of iPTH decrease were used: first, a PTH₁₅ of ≤150 pg/ml or, second, a relative PTH₁₅ of ≤30% less was used. Fifteen patients did not fulfil both criteria. In 13 of them (86.7%) iPTH_post was higher than 65 pg (true failure to decline). Of 114 patients who fulfilled the criteria, 108 (94.7%) had normal postoperative iPTH values (true decline). Absolute PTH₁₅ values of less than 150 pg/ml predicted normal postoperative iPTH levels in 77 of 78 patients.

A PTH₁₅ value of 150 pg/ml or less predicts operative success in patients with renal failure in 98.7% of cases, independently of the relative decay. In contrast, if the relative PTH₁₅ is higher than 30%, high postoperative PTH values are predicted with a probability of 86.7%. Although there remain some borderline cases, intraoperative iPTH measurement is accurate and also can be useful in patients with renal hyperparathyroidism.