Spurious decline in intraoperative parathyroid hormone: false positives in parathyroid surgery

Abstract

Objectives The aims of this study were to (1) describe a false-positive result using a highly sensitive intraoperative parathyroid hormone (PTH) assay in an adult patient with primary hyperparathyroidism and (2) discuss the potential pitfalls of revision parathyroid surgery and the implication of various localization techniques described in the literature. Methods A case report is described from a tertiary care university hospital. A literature review detailing diagnostic tools used to improve outcomes in parathyroid surgery is presented. The potential inaccuracies of intraoperative PTH assays are discussed. Results We present a 71-year-old woman with primary hyperparathyroidism who was referred to our institution for revision surgery. The patient had preoperative sestamibi imaging that localized a right inferior parathyroid lesion. Intraoperatively, a specimen consistent with parathyroid tissue was removed and sent for frozen section. The intraoperative PTH levels were noted to decrease from 154 pg/mL (preincision) to 28 pg/mL (20 minutes postexcision). The frozen section results were consistent with a lymph node. This stimulated a 4-gland exploration, which confirmed normal left superior and inferior parathyroid glands. A 1.5-cm right retroesophageal parathyroid was subsequently discovered and excised. Final intraoperative PTH levels were 20 pg/mL. Conclusion Rapid PTH assays have become the mainstay of parathyroid surgery at many institutions; however, despite their accuracy, false-positive results are known to occur. We present a case of an inaccurate decline in intraoperative PTH and use this case report as a means to highlight some potential pitfalls of the test.