VALIDATION, ROLE IN PERIOPERATIVE ASSESSMENT, AND CLINICAL-APPLICATIONS OF AN IMMUNORADIOMETRIC ASSAY FOR HUMAN CALCITONIN

We have evaluated a new immunoradiometric assay (IRMA) for calcitonin (CT) (Medgenix, Belgium). The detection limit of immunoreactive CT (IR -CT) was 2.8 pg/ml, and plasma levels of IR-CT of 134 healthy adults ( dynamic range, 2.8-1000 pg/ml) were <19 pg/ml (median 4.1 pg/ml). Both basal and pentagastrin-stimulated IR-CT levels were (30 pg/ml and wer e well separated from the levels in patients with medullary thyroid ca rcinoma (MTC) (46-29,000 pg/ml, n = 38). In preoperative plasma sample s in five patients with C-cell hyperplasia, CT IRMA confirmed the diag nosis, although in two patients RIA failed to detect a significant inc rease of IR-CT. By modifying the IRMA, we could identify residual tumo r tissues perioperatively in patients undergoing thyroidectomy for MTC . RIA of gel-permeation chromatography showed four IR-CT peaks, but IR MA had only three peaks, suggesting that IRMA is more specific. CT-IRM A is more specific, sensitive, robust, rapid, and reliable than RIA. I n addition, neat plasma can be used directly in a single step in CT-IR MA.