Calcium-stimulated calcitonin test for the diagnosis of medullary thyroid cancer: results of a multicenter study and comparison between different assays

BACKGROUND

A basal serum calcitonin (Ct) increase >100 pg/mL in patients with a thyroid nodule is consistent with the diagnosis of medullary thyroid cancer (MTC). In cases where the CT test have a slight to moderate increase, the calcium gluconate stimulation test is helpful to increase diagnostic accuracy. However, reliable cut-offs for calcium-stimulated Ct are still lacking. The aim of this study was to evaluate the sex-specific calcium-stimulated Ct cutoffs for the diagnosis of MTC in a multicenter series. A comparison between different Ct assays has been also performed.

METHODS

90 subjects undergone calcium-stimulated Ct for a suspected MTC in 5 Endocrine Units between 2010-2021 were retrospectively analyzed. Serum Ct concentrations were assessed by immunoradiometric (IRMA) or chemiluminescence (CLIA) assays.

RESULTS

MTC was diagnosed in 37 (41.1%) and excluded in 53 (58.9%) patients. The best calcium-stimulated Ct cut-off to identify MTC was 611 pg/mL in males (AUC =0.90, 95% CI (0.76;1) and 445 pg/mL in females (AUC=0.79, 95% CI (0.66;0.91). Logistic regression analysis showed that both basal (OR 1.01, P=0.003) and peak Ct after stimulation (OR 1.07, P=0.007) were significantly associated with MTC, together with sex (OR=0.06, P<0.001). The "Ct assay" variable was also considered in the logistic regression model, but it was not significantly associated with MTC (OR=0.93, P=0.919).

CONCLUSIONS

This study indicates that calcium test could be helpful to identify patients with early-stage MTC and those without MTC. A Ct value of 611 pg/mL in males and 445 pg/mL in females are proposed as the optimal Ct cut-offs at the stimulation test.

[Post-heparin lipase activity in beta-thalassemia major: preliminary data]

We studied serum lipids and post-heparin triglyceride lipase activities in 8 patients with Beta-Thalassaemia Major, under high transfusion programme and regular chelation therapy and in 8 control subjects. Total cholesterol and HDL-cholesterol were significantly lower in patients with Cooley's anaemia, whereas triglyceride levels did not differ in the two groups. Post-heparin triglyceride lipase activities were determined according with the method of Krauss et A1. using glyceryl-tri-(1-14C)oleate as substrate and NaCl to inactivate the extrahepatic lipase. These enzymatic activities (both hepatic and extrahepatic) resulted significantly lower in thalassaemic patients. We suppose that the decreased levels of these enzymatic activities could play a role in determining the decrease of HDL-cholesterol that we observed in our thalassaemic patients.

[Changes in HDL subfractions in patients with type I diabetes mellitus before and after metabolic control]

In order to further investigate the behaviour of high density lipoproteins in diabetes mellitus, we studied HDL subclasses, HDL2 and HDL3, in 10 patients with newly detected, untreated insulin-deficient diabetes before starting insulin treatment and after getting a good metabolic control. We used the extractive method of Abell to determine HDL-cholesterol after LDL and VLDL precipitation with polyanions and HDL3-cholesterol after HDL2 precipitation with dextransulphate 15,000 m.w. After insulin therapy, we observed a significant increase in HDL-cholesterol and a decrease in serum triglycerides. Only HDL2-cholesterol, but not HDL3-cholesterol, raised; moreover, we found a significant inverse relationship between HDL-cholesterol (and also HDL2-cholesterol) and triglycerides. So, we think that an increase of lipoprotein lipase activity, owing to insulin treatment, could account for our results.

[HDL2 and HDL3 cholesterol in hepatic cirrhosis]

In order to further investigate plasma lipoproteins abnormalities secondary to serious liver damage, we studied plasma lipids and lipoproteins, and in particular HDL subfractions (HDL2, HDL3), in 12 patients with cirrhosis of the liver and in 12 sex, age and weight matched healthy volunteers. Enzymatic methods were used to determine total cholesterol and triglycerides, while the extractive method of Abell et al. was used for the determination of HDL-cholesterol levels after LDL and VLDL precipitation with polyanions (MnCl2 and Na-heparin) and of HDL3-cholesterol values after HDL2 precipitation with dextran-sulphate 15,000 m.w. Total cholesterol and HDL-cholesterol levels were significantly lower in cirrhotic patients compared to normal subjects. We must emphasize that only HDL3-cholesterol was decreased in cirrhotics, whereas HDL2-cholesterol values were normal or high. We suggest that a diminished activity of hepatic triglyceride lipase might account for the decrease in HDL3-cholesterol in liver cirrhosis.