Intraoperative measurement of intact parathyroid hormone in renal hyperparathyroidism by an inexpensive routine assay

Abstract.

Although the kinetics of intraoperative intact parathyroid hormone (iPTH) are well characterised in primary hyperparathyroidism, no data are available for patients with renal hyperparathyroidism and renal insufficiency, partially because of the high costs of intraoperative quick iPTH measurement. Therefore we evaluated an inexpensive laboratory test with a duration of 18 min for intraoperative use and measured iPTH intraoperatively in 34 patients with renal hyperparathyroidism. Samples were taken before and 5 min and 15 min after parathyroid resection. Blood samples were put on ice immediately and sent to the hospital central laboratory via a pneumatic tube system. The first 76 probes were measured in parallel using three assays: the Nichols Quick PTH, the Roche Elecsys and the Biermann Immulite assay. The subsequent samples were only measured using the Elecsys assay. Determination of iPTH from 76 samples showed a correlation coefficient of 0.997 between the Immulite and Elecsys assay and a correlation coefficient of 0.987 for the Nichols Quick PTH and the Elecsys test. In renal hyperparathyroidism the mean iPTH was 26±2% of the starting value 5 min after subtotal parathyroidectomy and 18±2% after 15 min. Renal function influenced absolute iPTH values in patients with renal hyperparathyroidism but not relative changes. In patients with terminal renal insufficiency iPTH decreased from 615±57 pg/m before preparation to 109±13 pg/ml 15 min after subtotal resection. In contrast in patients after kidney transplantation iPTH decreased from a lower starting value of 341±94 pg/ml to 58±9 pg/ml after 15 min. The iPTH kinetics showed a biphasic clearance of iPTH with an initial dominant half-life of 3.2 min and a terminal half-life of 29.2 min. Half-life did not correlate with renal function. All operations were successful as indicated by an adequate drop in PTH (from 709±92 pg/ml preoperatively to 22±6 pg/ml at discharge) and calcium (from 2.57±0.04 mmol/l to 2.32±0.04 mmol/l). In conclusion, intraoperative measurement of iPTH is also reliable in patients with renal hyperparathyroidism. Elimination kinetics are similar to that in patients with primary disease. However, the half-life was not influenced by renal function. The availability of a quick, inexpensive, routine iPTH test might expand its use to renal hyperparathyroidism, specifically for surgical decisions in problem cases.