title: A spike in parathyroid hormone during neck exploration may cause a false-negative intraoperative assay result.
abstract: OBJECTIVE
  We hypothesize that false-negative results using the rapid intraoperative parathyroid hormone (IOPTH) assay can be caused by spikes in the level of parathyroid hormone that occur during mobilization of the adenoma.
  
  
  METHODS
  Retrospective analysis of a case series.
  
  
  METHODS
  University tertiary care center.
  
  
  METHODS
  Ten consecutive patients with primary hyperparathyroidism.
  
  
  METHODS
  All patients underwent neck exploration with IOPTH monitoring. Using a sampling protocol described in the literature, IOPTH values were checked at the time of incision, during mobilization of the adenoma, and 10 minutes after resection of the adenoma.
  
  
  METHODS
  Patients were evaluated for adequate parathyroid tissue excision as determined by IOPTH levels and examination of ipsilateral glands. All patients had normal serum calcium values documented postoperatively. Parathyroid hormone half-life was calculated assuming first-order kinetic decay.
  
  
  RESULTS
  Nine patients had an appropriate decline in IOPTH with a mean +/- SD parathyroid hormone half-life of 3.9 +/- 1.08 minutes. Mobilization of the adenoma resulted in a spike in the IOPTH value, with 1 patient's value increasing from a baseline of 95.5 pg/mL (10.1 pmol/L) to 751 pg/mL (79.1 pmol/L). Another patient who was confirmed to have a solitary adenoma had a false-negative postexcision value. A spike in IOPTH that occurred during neck dissection was not detected by the sampling protocol and explains the false-negative value. A literature review revealed that most protocols check baseline values early in the operation and are at risk for false-negative results due to a spike from mobilization of the adenoma.
  
  
  CONCLUSIONS
  These data demonstrate that false-negative IOPTH assay findings can result from a spike in parathyroid hormone level during exploration, which may go unrecognized if baseline values are measured during the early stages of mobilization of the adenoma. We have altered our assay protocol and have begun measuring IOPTH at the time of neck incision, at the time the adenoma is completely removed (time zero [t(0)]), and 10 minutes after excision.
authors.affiliation: Department of Surgery, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: G P
authors.initials: GP
authors.lastname: Yang
authors.forename: S
authors.initials: S
authors.lastname: Levine
authors.forename: R J
authors.initials: RJ
authors.lastname: Weigel
mesh_terms: D000236:Adenoma / Q000097:blood / Q000150:complications / Q000601:surgery*; D000328:Adult; D000368:Aged; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood / Q000209:etiology; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010281:Parathyroid Hormone / Q000097:blood*; D010282:Parathyroid Neoplasms / Q000097:blood / Q000150:complications / Q000601:surgery*; D016105:Parathyroidectomy / Q000009:adverse effects; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D010281:Parathyroid Hormone