title: Interpretation of intraoperative parathyroid hormone monitoring in patients with baseline parathyroid hormone levels of <100 pg/mL.
abstract: BACKGROUND
  Common guidelines for intraoperative parathyroid hormone (IOPTH) interpretation are based on clearly elevated baseline parathyroid hormone (PTH) values. We hypothesize that patients with low-baseline levels (<100 pg/mL) have a higher incidence of multigland disease (MGD) and display differences in PTH kinetics compared with patients with high-baseline levels.
  
  
  METHODS
  We retrospectively reviewed the cases of 1151 patients with primary hyperparathyroidism who underwent parathyroidectomy with IOPTH monitoring. Of these, 141 patients had low-baseline values. Multiple comparisons were made between the low-baseline and high-baseline groups.
  
  
  RESULTS
  Twenty-six percent of the low-baseline patients had MGD versus 15% of the high-baseline patients (P = .002). The PTH kinetics differed between groups after gland excision at both 5 and 10 minutes. Adherence solely to the "50% rule" during minimally invasive parathyroidectomy potentially would have missed 25% of patients with MGD in the low-baseline group versus 10% in the high-baseline group; 5.7% of the low-baseline patients had persistent or recurrent hypercalcemia versus 2.9% of the high-baseline patients.
  
  
  CONCLUSIONS
  MGD is significantly more prevalent among low-baseline patients, and PTH kinetics are somewhat different between groups. The current guidelines that are used for IOPTH monitoring may not be ideal for use in this low-baseline group and will likely need to be revised after further study of this group of patients.
authors.affiliation: University of Texas Health Science Center, Division of General Surgery, MC7842, 7703 Floyd Curl Dr, San Antonio, TX 78229, USA. millerb2@uthscsa.edu
authors.forename: Barbra S
authors.initials: BS
authors.lastname: Miller
authors.forename: Barry G
authors.initials: BG
authors.lastname: England
authors.forename: Matthew
authors.initials: M
authors.lastname: Nehs
authors.forename: Richard E
authors.initials: RE
authors.lastname: Burney
authors.forename: Gerard M
authors.initials: GM
authors.lastname: Doherty
authors.forename: Paul G
authors.initials: PG
authors.lastname: Gauger
mesh_terms: D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood* / Q000175:diagnosis / Q000601:surgery*; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D049451:Nomograms; D010280:Parathyroid Glands / Q000473:pathology* / Q000601:surgery; D010281:Parathyroid Hormone / Q000097:blood*; D016105:Parathyroidectomy / Q000379:methods; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D010281:Parathyroid Hormone