Diagnostic Performance of Preoperative Calcitonin and Procalcitonin Tests for Differential Diagnosis of Medullary Thyroid Cancer

Abstract

Medullary thyroid cancer (MTC) shows a relatively poor prognosis among thyroid cancers. Though calcitonin has been used as a diagnostic marker for MTC, it has disadvantages including poor sample stability and discrepancies among results by assay. This study aimed to compare the usefulness of preoperative calcitonin and procalcitonin (PCT) in the diagnosis of MTC. Serum calcitonin and PCT levels were measured before thyroidectomy from MTC (n = 23) and other types of thyroid cancers in patients (n = 1308). Diagnostic performances of calcitonin and PCT for discerning MTC were estimated. In a multivariate analysis, preoperative calcitonin level was independently associated with the diagnosis of MTC, whereas PCT was not. Calcitonin and PCT, respectively, exhibited area under the curve values of 0.997 and 0.979 for the diagnosis of MTC, without significant differences. For calcitonin, the sensitivity, specificity, and positive and negative predictive values were 0.957, 0.992, 0.688, and 0.999, respectively, at a cut-off of 7.2 pg/mL. The corresponding values for PCT were 0.913, 0.995, 0.778, and 0.998 at a cut-off of 0.19 ng/mL. Preoperative calcitonin and PCT showed similar diagnostic utility for MTC. Depending on the patient's clinical status and laboratory environment, these tests can be used as complementary methods for detecting MTC.

Keywords: calcitonin; diagnostic performance; medullary thyroid cancer; procalcitonin.

Figure 1

Diagnostic performances of calcitonin, procalcitonin (PCT), and carcinoembryonic antigen (CEA) for the discrimination of medullary thyroid cancer (MTC) from other histologic types of thyroid cancer. Calcitonin, PCT, and their combination showed excellent diagnostic performance for MTC diagnosis (23 cases and 1308 controls) with the area under the curve (AUC) values greater than 0.97, and the AUC values of the tests were similar to one another (A). In the subgroup of patients with CEA results (13 cases and 50 controls), the AUC values of calcitonin, PCT, and CEA were 0.989, 0.936, and 0.912, respectively, but they were not statistically different (B).