title: Analytical and clinical validation of parathyroid hormone (PTH) measurement in fine-needle aspiration biopsy (FNAB) washings.
abstract: BACKGROUND
  Parathyroid hormone (PTH) quantitation in fine needle aspirate biopsy (FNAB) saline washings complements current modalities for parathyroid tissue localization.
  
  
  OBJECTIVE
  To establish the performance characteristics of the Roche Elecsys intact PTH immunoassay in FNAB needle washings and its diagnostic performance for the identification of parathyroid tissue.
  
  
  METHODS
  Accuracy, precision, reportable range, and analytical specificity and sensitivity for the intact PTH immunoassay in FNAB needle washings were established. For clinical validation, 93 specimens from 79 patients were evaluated. Diagnostic cut-offs were established via receiver operator characteristic (ROC) curve analysis. Performance of PTH in FNAB needle washings was compared to cytology.
  
  
  RESULTS
  Measurement of the PTH in FNAB needle washings demonstrated a matrix interference that was overcome by supplementation of the samples with a protein based matrix prior to analysis. ROC area under the curve (AUC) was 0.96 for PTH in FNAB needle washings. A PTH concentration ≥100pg/mL showed 100% specificity and 82% sensitivity for identifying parathyroid tissue. On histology-confirmed parathyroid specimens, 21/38 (55%) were correctly identified by cytology; whereas 31/38 (82%) were identified by PTH.
  
  
  CONCLUSIONS
  Measurement of PTH in FNAB washings complements cytology for identification of parathyroid tissue. Analytical validation to exclude interference in the PTH immunoassay and proper localization of the parathyroid tissue by ultrasound is necessary to ensure the robustness of the method.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Hemamalini
authors.initials: H
authors.lastname: Ketha
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Lasho
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA. Electronic address: algecirasschimnich.alicia@mayo.edu.
authors.forename: Alicia
authors.initials: A
authors.lastname: Algeciras-Schimnich
mesh_terms: D001707:Biopsy, Needle; D006801:Humans; D007118:Immunoassay; D057230:Limit of Detection; D010281:Parathyroid Hormone / Q000032:analysis*; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D010281:Parathyroid Hormone
keywords: FNAB needle washings; Fine needle aspirate biopsy (FNAB); Parathyroid hormone (PTH)