Development and Evaluation of a Combined Immunoassay Method Based on a Stable Isotope Tagging Strategy and Inductively Coupled Plasma Mass Spectrometry for Detecting Human Chorionic Gonadotropin.

Background: The development of a combined immunoassay method, based on a stable isotope tagging strategy and inductively coupled plasma mass spectrometry (ICP-MS), has created options for quantitative bioanalysis. The aim of the study was to develop a combined immunoassay, featuring ICP-MS and a stable element labeling strategy, for the detection of human chorionic gonadotropin (HCG), and developed methodology applicable for clinical practice.

Methods: In accordance with guidelines published by the Clinical and Laboratory Standards Institute (CLSI), we developed our assay and then evaluated its analytical performance, including the limit of detection (LOD), the upper limit of quantification (ULoQ), linearity, precision, recovery, cross reactivity, and interference. Next, we collected 130 clinical samples for analysis with the new assay. The data derived from our assay were then compared with those derived by an existing electrochemiluminescence immunoassay (ECLIA).

Results: The LOD of the assay was 0.33 mIU/mL and the ULoQ was 11,300 mIU/mL. The coefficient of determina-tion of linearity was higher than 0.99 in the range of 1 to 8,917 mIU/mL (R2 = 0.9964). The obtained recoveries ranged from 97.08% to 103.50%, while the intra-assay imprecision of high value samples and low value samples were 2.97% and 6.08%, respectively. The inter-assay imprecision of high value samples and low value samples were 3.98% and 7.08%, respectively. Interference test results deviated by less than ± 10% in the presence of hemoglobin ≤ 2 g/L, bilirubin ≤ 274 mol/L, or triglycerides ≤ 37 mmol/L. Compared with the commercial ECLIA method for clinical sample detection, the proposed method showed a significant correlation (R2 = 0.9770) and satisfactory agreement.

Conclusions: The combination of ICP-MS and a stable element labeling based immunoassay for HCG detection was established successfully and the general performance of this system was acceptable, thus indicating that the assay has potential for the clinical application.