Is basal ultrasensitive measurement of calcitonin capable of substituting for the pentagastrin-stimulation test?


Correspondence: Geraldine Pina, Centre de Médecine Nucléaire, Groupement Hospitalier Est, 59 boulevard Pinel, 69677 Bron Cedex, France. Tel.: +33 (0) 4 72 35 72 77; Fax: +33 (0) 4 72 35 73 45;




To evaluate a second-generation assay for basal serum calcitonin (CT) measurements compared with the pentagastrin-stimulation test for the diagnosis of inherited medullary thyroid carcinoma (MTC) and the follow-up of patients with MTC after surgery. Recent American Thyroid Association recommendations suggest the use of basal CT alone to diagnose and assess follow-up of MTC as the pentagastrin (Pg) test is unavailable in many countries.


Multicentric prospective study.


A total of 162 patients with basal CT <10 ng/l were included: 54 asymptomatic patients harboured noncysteine ‘rearranged during transfection’ (RET) proto-oncogene mutations and 108 patients had entered follow-up of MTC after surgery.


All patients underwent basal and Pg-stimulated CT measurements using a second-generation assay with 5-ng/l functional sensitivity.


Ninety-five per cent of patients with basal CT ≥5 ng/l and 25% of patients with basal CT <5 ng/l had a positive Pg-stimulation test (Pg CT >10 ng/l). Compared with the reference Pg test, basal CT ≥5 ng/l had 99% specificity, a 95%-positive predictive value but only 35% sensitivity (< 0·0001). Overall, there were 31% less false-negative results using a 5-ng/l threshold for basal CT instead of the previously used 10-ng/l threshold.


The ultrasensitive CT assay reduces the false-negative rate of basal CT measurements when diagnosing familial MTC and in postoperative follow-up compared with previously used assays. However, its sensitivity to detect C-cell disease remains lower than that of the Pg-stimulation test.