Objective: To report the recent development and validation of a sensitive 15-minute immunochemiluminometric assay (ICMA) of parathyroid hormone (PTH). Design: The characteristics and applications of a new ''rapid'' PTH ICMA are described, and the advantages in comparison with other assays are discussed. Material and Methods: The 15-minute PTH ICMA was achieved by using a higher incubation temperature (45 degrees C rather than room temperature) and a concentration of tracer antibodies that was 5 times that in the regular 18-hour assay. The sensitivity, recovery, and linearity of dilution of the rapid ICMA were assessed, as was its ability to reflect intraoperative changes in PTH concentration after parathyroidectomy in patients with hyperparathyroidism. Results: The sensitivity of the ICMA was 0.3 pmol/L in comparison with 0.08 pmol/L for the regular 18-hour assay (normal range, 1.0 to 5.0). The recovery of added PTH was 84% by using ethylenediaminetetraacetic acid-plasma as the specimen. Moreover, the linearity of specimens after dilution was good. The assay demonstrated a rapid response to parathyroid gland removal. In most patients, PTH levels declined precipitously (to less than 30% of basal values) within 5 minutes after parathyroid resection. PTH levels remained low to undetectable at 10 and 20 minutes after excision. Conclusion: This rapid PTH ICMA may be of assistance to endocrine surgeons in the monitoring of PTH function after both parathyroid and thyroid surgical procedures.
