title: Calcitonin measurement and immunoassay interference: a case report and literature review.
abstract: Calcitonin (CT) is currently the most sensitive serological marker of C-cell disease [medullary thyroid carcinoma (MTC) and C-cell hyperplasia]. Starting with a report on a case that occurred at our institution, this review focuses on trying to explain the reasons behind the poor specificity and sensitivity of the various CT immunoassays. A 15-year-old patient was referred to our institution in May 2014 for moderately elevated CT levels. Thyroid ultrasonography (US) documented a colloidal goiter. Secondary causes of the hypercalcitoninemia (hyperCT) were ruled out. The mismatch between the clinical picture and the laboratory results prompted us to search for other reasons for the patient's high CT levels, so we applied the heterophilic blocking tube (HBT) procedure to the patient's sera before the CT assay. Using this pretreatment step, his serum CT concentration dropped to <1 ng/L, as measured at the same laboratory. Measuring plasma CT has an important role in screening for C-cell disease, but moderately elevated serum CT levels need to be placed in their clinical context, bearing in mind all the secondary causes of C-cell hyperplasia and the possibility of laboratory interference, before exposing patients to the risks and costs of further tests.
authors.forename: Simona
authors.initials: S
authors.lastname: Censi
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Cavedon
authors.forename: Sara Watutantrige
authors.initials: SW
authors.lastname: Fernando
authors.forename: Susi
authors.initials: S
authors.lastname: Barollo
authors.forename: Loris
authors.initials: L
authors.lastname: Bertazza
authors.forename: Laura
authors.initials: L
authors.lastname: Zambonin
authors.forename: Martina
authors.initials: M
authors.lastname: Zaninotto
authors.forename: Diego
authors.initials: D
authors.lastname: Faggian
authors.forename: Mario
authors.identifier: http://orcid.org/0000-0002-0270-1711
authors.initials: M
authors.lastname: Plebani
authors.forename: Caterina
authors.initials: C
authors.lastname: Mian
mesh_terms: D000293:Adolescent; D002116:Calcitonin / Q000097:blood*; D006801:Humans; D007118:Immunoassay; D008163:Luminescent Measurements; D008297:Male
chemical_list: D002116:Calcitonin