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

OBJECTIVE: 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. DESIGN: Multicentric prospective study. PATIENTS: 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. MEASUREMENT: All patients underwent basal and Pg-stimulated CT measurements using a second-generation assay with 5-ng/l functional sensitivity. RESULTS: 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 (P < 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. CONCLUSION: 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.

Selection of patients with solitary thyroid nodules for operation.

OBJECTIVE: To improve the preoperative selection for operation of patients with solitary thyroid nodules. DESIGN: Prospective cohort study. SETTING: University hospital, France. PATIENTS: 155 consecutive patients who presented with solitary thyroid nodules and were operated on. INTERVENTIONS: Clinical examination, ultrasound examination, fine needle aspiration biopsy, followed by total thyroid lobectomy with frozen section and final histological examination. MAIN OUTCOME MEASURE: Correct prediction of thyroid carcinoma or benign adenoma. RESULTS: A logistic regression analysis indicated that absence of rim (p < 0.002), solid and hypoechoic feature (p < 0.003) and malignant or suspicious fine needle aspiration biopsy results (p < 0.0001) were significantly associated with malignancy. Selection for operation by the logistic model would save 40 of 73 patients from operation and 40 of 59 from unnecessarily radical operation. It would detect a similar number of cancers as a strategy based solely on fine needle aspiration cytology. CONCLUSIONS: A combination of the available diagnostic methods provides substantial benefit in the preoperative selection of patients with an isolated thyroid nodule.