Stability assessment of serum tumour markers: Calcitonin, chromogranin A, thyroglobulin and anti-thyroglobulin antibodies.

BACKGROUND: There is limited published data on the stability of calcitonin, chromogranin A, thyroglobulin and anti-thyroglobulin antibodies in serum. The aim of this study was to determine stability at three temperature conditions over 7 days, reflecting current laboratory practices.

METHODS: Surplus serum was stored at room temperature, refrigerated and in the freezer; for 1, 3, 5 and 7 days. Samples were analysed in batch and analyte concentrations compared to that of a baseline sample. Measurement Uncertainty of the assay was used to determine the Maximal Permissible Difference and thus the stability of the analyte.

RESULTS: Calcitonin was found to be stable for at least 7 days in the freezer but only 24 h refrigerated. Chromogranin A was stable for 3 days when refrigerated and only 24 h at room temperature. Thyroglobulin and anti-thyroglobulin antibodies were stable under all conditions for 7 days.

CONCLUSION: This study has enabled the laboratory to increase the add-on time limit of Chromogranin A to 3 days, and up to 60 min for calcitonin and inform optimal storage and transportation conditions for referring specimens.