CALCA and medullary thyroid gland carcinoma: When applying the respective cut-off values showing the best diagnostic accuracy for each assay (7.2 pg/mL for calcitonin and 0.19 ng/mL for PCT), one case among 23 MTC cases was positive only for calcitonin, another case was negative for both calcitonin and PCT, and the rest of the 21 patients were positive for both calcitonin and PCT.