Analytical Performance Evaluation of a New Calcitonin Assay

Abstract

Background: The use of efficient laboratory calcitonin (CT) testing is required for optimal management of medullary thyroid carcinoma. Several pitfalls are related to the calcitonin laboratory assays and a careful evaluation is needed. We report the analytical performances of the new Siemens ADVIA-Centaur-CALCT (CT-XPT) assay and its comparison with our standard method DiaSorin-Calcitonin-II-Gen (CT-LIA) assay.

Methods: Analytical performance of the CT-XPT-assay, limit of blank (LOB), limit of detection (LOD), and limit of quantification (LOQ), were determined. We also evaluated the in vitro stability of the sample, together with the linearity and percentage recovery.

Results: The CT-XPT-assay showed a better detection limit than the CT-LIA assay, with lower values of LOB (0.86 pg/mL vs 1.00 pg/mL) and LOQ (1.65 pg/mL vs 3.00 pg/mL). Both values were in agreement with those reported by the manufacturer. Within- and between-run precision demonstrated a good concordance of results. Regarding the in vitro stability of CT, the low CT concentration sera showed a much greater decrease in CT levels compared to the high concentration sera. Correlation studies showed a good correlation between the two methods (Kappa Cohen coefficent, KC: 0.68, agreement % for male: 89.58%; KC: 0.63; agreement % for female: 88.33%).

Conclusions: Our findings showed a good correlation between the CT-LIA and CT-XPT methods. Moreover, we demonstrated that the analytical performance of the CT-XPT assay, together with its technical specifications, could represent major features of the CT-XPT method. Collectively, the technical evaluation and the analytical results described in the presented paper highlight that the novel CT-XPT is a valid method for CT testing in a clinical diagnostic setting.

Keywords: calcitonin; laboratory assay; medullary thyroid carcinoma.