Novel Parathyroid Hormone (1-84) Assay as Basis for Parathyroid Hormone Monitoring in Renal Hyperparathyroidism

HYPOTHESIS: Cross-reactivity of parathyroid hormone (PTH) fragments with immunometric "intact" PTH assays limited the use of intraoperative PTH monitoring in renal hyperparathyroidism. A new assay generation measuring whole PTH (1-84) should be able to predict complete or incomplete resection of hyperfunctioning parathyroid tissue. DESIGN: Consecutive series for evaluation of intraoperative PTH monitoring using a second-generation assay. SETTING: University hospital section of endocrine surgery. PATIENTS: Twenty-two patients received hemodialysis; 9 patients showed good and 4 patients reduced graft function after kidney transplantation. INTERVENTIONS: Total parathyroidectomy, central neck dissection, bilateral thymectomy, and immediate autotransplantation was the standardized approach in 35 consecutive patients. Blood samples were drawn before incision and at 5-minute intervals after excision of the last gland. Stored samples were analyzed using a "second-generation" assay (Bio-Intact PTH [1-84]; Nichols Institute Diagnostics, San Clemente, Calif). Parathyroidectomy was classified as total, subtotal, or insufficient according to first-generation intact PTH values in the first postoperative week. MAIN OUTCOME MEASURES: Intraoperative ability to predict total, subtotal, or incomplete parathyroidectomy. RESULTS: Independent of renal function, Bio-Intact PTH dropped into the normal range in all patients with total and subtotal resections after a maximum of 20 minutes. It indicated insufficient parathyroidectomy in 4 (80%) of 5 patients. One failure was caused by devascularization of remaining parathyroid tissue. An intraoperative differentiation between total and subtotal resection was not possible. CONCLUSIONS: Intraoperative monitoring with quick, second-generation assays for PTH (1-84) seems to be a valuable new tool in surgery for renal hyperparathyroidism because a more accurate differentiation between sufficient and insufficient parathyroidectomy may be achieved. An intraoperative decision about the need for immediate or delayed autotransplantation seems impossible because a differentiation between total or subtotal parathyroidectomy cannot be made. Because of possible devascularization of parathyroid tissue, Bio-Intact PTH monitoring can only be interpreted in the context of the operative findings.