Amber Mater1,2,3, Anita Boelen2,3,4, Annemieke Heijboer1,2,3,4, Jacquelien Hillebrand2,3
(1) Amsterdam UMC location Vrije Universiteit Amsterdam, Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam, The Netherlands. (2) Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands. (3) Amsterdam UMC location University of Amsterdam, Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam, The Netherlands. (4) Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands
Introduction:
Medullary thyroid cancer (MTC) originates from parafollicular cells of the thyroid gland. These cells secrete the peptide hormone calcitonin, which can be measured in serum using (automated) immunoassays to monitor MTC. The stability of serum calcitonin is not well understood and may affect the concentrations measured. In addition, calcitonin immunoassays are poorly standardized making it difficult to compare results between assays.
Methods:
In this study we evaluated the stability of calcitonin in serum upon storage at room temperature and upon multiple freeze-thaw cycles. Additionally, we compared calcitonin concentrations of 40 serum samples analyzed using three automated calcitonin immunoassays.
Results:
We observed that calcitonin concentrations in serum remain stable for up to three hours at room temperature and for up to five freeze-thaw cycles. The immunoassay comparison showed good agreement between the Cobas e601 (Roche Diagnostics) and the Liaison XL (Diasorin) (slope of 1.02). However, the Atellica IM 1600 (Siemens Healthineers) measured approximately 13% higher calcitonin concentrations when compared to both Cobas e601 and Liaison XL.
Conclusion:
Calcitonin in serum is stable for three hours at room temperature and upon five freeze-thaw cycles. It is advised to use the same assay to monitor calcitonin concentrations in patients, as serum calcitonin concentrations are assay-dependent.