Endocrine Abstracts

Introduction: Calcitonin (Ct) is the most sensitive serological marker of medullary thyroid carcinoma (MTC). Its assay however is plagued by numerous interferences with consequent high risk of false diagnoses and unnecessary thyroidectomy. Numerous studies have been conducted to identify potential alternative MTC serum markers, among which the most promising one is procalcitonin (proCt). This work aims to present the possible use of proCt in unmasking cases of false hypercalcitoninemia (hyperCt).

Case reports: 4 adult patients were referred to us for recent and incidentally finding of hyperCt. The first patient was a woman with autoimmune thyroiditis, the second one was a smoker woman with multinodular goiter, the third one was a man with rheumatoid arthritis and the last one was a thyroidectomized woman with pancreatic lesion. Calcitonin assay (Immunolite 2000 automated platform, Siemens, Healthcare Diagnostics), calcium gluconate stimulation test (Ca-test) and proCt assay were performed in all patients. Ct after 1:2 and 1:4 dilution, precipitation on PEG and heterophilic Ab test (HBT) were performed in patients #1 and #2. Ct assay on another automated platform (LIAISON Diasorin) was performed in all patients except for patient #4. In patient #1, #2 and #3, Ct assays during Ca-test were substantially unchanged, basal Ct value was lower using a different automated platform and proCt was always undetectable. In patients #1 and #2 the value of basal and stimulated Ct after serial dilution (1:2 and 1:4) were lower than the values obtained in toto. Similar results were also obtained after precipitation on PEG and HBT. Based on this data, we concluded for false hyperCt caused by laboratory interferences. On the contrary, patient #4 presented increased Ct values after the Ca-test, detectable ProCt value and frankly increased Ct values performed on pancreatic lesion eluate, so we concluded for a pancreatic calcitonin-secreting neuroendocrine tumor (NET) (Table 1)

Conclusion: Undetectable proCt values in patients with hyperCt are suggestive of false hyperCt. ProCt could help clinicians in unmasking cases of spurious hyperCt, without the need to perform dilution, precipitation or HBT.