Need for Revision of Diagnostic Limits for Medullary Thyroid Carcinoma with a New Immunochemiluminometric Calcitonin Assay

Abstract

Calcitonin is the most sensitive tumor marker for both diagnosis and postoperative surveillance of medullary thyroid carcinoma (MTC).1 Healthy control individuals virtually always have a serum calcitonin concentration 100 ng/L are >90% specific for a diagnosis of C-cell disease, either C-cell hyperplasia or MTC (1). These diagnostic limits were established on the basis of data from studies that used the manual Cisbio immunoradiometric calcitonin assay and were subsequently validated for the Nichols calcitonin assay(2). Many centers now use the Liaison assay (Diasorin) as an alternative to the discontinued Nichols assay. Bieglmayer et al. have shown that the Liaison calcitonin assay is positively biased compared with the Nichols assay (3). The manufacturer’s product insert for the Liaison assay currently recommends a basal calcitonin concentration of >10 ng/L as the diagnostic limit for further investigation for MTC, despite the fact that the upper reference limit for males (18.6 ng/L) exceeds this limit. A recent study published in Clinical Chemistry proposed revision of the 10-ng/L limit for measuring basal calcitonin with the Liaison assay(4). The Liaison assay is a 1-step direct, 2-site …