Development and evaluation of an element-tagged immunoassay coupled with inductively coupled plasma mass spectrometry detection: can we apply the new assay in the clinical laboratory?

Introduction Element-tagged immunoassay coupled with inductively coupled plasma-mass spectrometry (ICP-MS) detection has the potential to revolutionize immunoassay analysis in clinical detection; however, a systematic evaluation with the standard guidelines of the assay is needed to ensure its performance meets the requirements of the clinical laboratory. Methods Carcinoembryonic antigen (CEA) was chosen for analysis using the proposed method. A systematic evaluation of the proposed assay was carried out according to the Clinical and Laboratory Standards Institute (CLSI). The 469 clinical samples were analyzed using the new method and compared with the electrochemiluminescent immunoassay (ECLIA) method. Results The measurement range of the assay was 1-900 ng/mL, with a detection limit of 0.83 ng/mL. The inter-assay and intra-assay imprecision were 4.67% and 5.38% with high concentration samples, and 9.27% and 17.64% with low concentration samples, respectively. The cross-reactivity (%) for different antigens was less than 0.05%, and the recovery was between 94% and 108%. Percentage deviation of all the dilutions was less than 12.5% during linearity estimation. The interference bias caused by different substances was less than 10%. The reference interval of the assay was 0-4.442 ng/mL. Comparison with the commercial ECLIA method for clinical sample detection, the proposed method showed a correlation of 0.9878 and no significant differences between the methods were observed (p = 0.6666). Conclusions The ICP-MS based immunoassay was successfully developed, and the analytical performance of the assay met the requirements of the CLSI, which fully proved the clinical transferability and application of the new method.

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.

A preliminary study for the establishment of a reference interval for vitamin B12 in China after performance verification of a second-generation ECLIA kit.

BACKGROUND: The second-generation electrochemiluminescence immunoassay (ECLIA) kit of vitamin B12 is widely used in clinical laboratories, and the establishment of a reference interval (RI) is essential to provide the basis for clinical monitoring. The purpose of this study was to establish a laboratory RI for vitamin B12 in China and at the same time verify the method performance of the second-generation kit. METHODS: The verification of the method performance was conducted according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Based on these guidelines, a total of 580 serum samples were collected, and 391 serum samples were used for the establishment of the RI according to CLSI guidelines. The subjects were grouped by sex and age. The age groups were as follows: 21-40, 41-60, and 61-80 years. The RI was defined by nonparametric 2.5th and 97.5th percentile intervals. RESULTS: The performance of the second-generation kit of vitamin B12 from the Roche Cobas E602 system was in compliance with laboratory requirements. Serum vitamin B12 levels conformed to a non-Gaussian distribution. Harris-Boyd's test did not indicate partitioning for different age and gender group. Besides, there was no significant difference between different age groups (P = .07) and gender groups (P = .2002). The RI for healthy Chinese adults (aged 21-80 years) calculated by the nonparametric method was 250.8-957.1 pg/mL. CONCLUSIONS: The reference range of vitamin B12 was established, which provided a theoretical basis for the clinical application and monitoring of vitamin B12 detection.

Evaluation of an Element-Tagged Duplex Immunoassay Coupled with Inductively Coupled Plasma Mass Spectrometry Detection: A Further Study for the Application of the New Assay in Clinical Laboratory.

BACKGROUND: Element-tagged immunoassay coupled with inductively coupled plasma mass spectrometry (ICP-MS) detection has the potential to revolutionize immunoassay analysis for multiplex detection. However, a further study referring to the standard evaluation and clinical sample verification is needed to ensure its reliability for simultaneous analysis in clinical laboratories. METHODS: Carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) were chosen for the duplex immunoassay. The performance of the assay was evaluated according to guidelines from the Clinical and Laboratory Standards Institute (CLSI). Moreover, reference intervals (RIs) of CEA and AFP were established. At last, 329 clinical samples were analyzed by the proposed method and results were compared with those obtained with electrochemiluminescent immunoassay (ECLIA) method. RESULTS: The measurement range of the assay was 2-940 ng/mL for CEA and 1.5-1000 ng/mL for AFP, with a detection limit of 0.94 ng/mL and 0.34 ng/mL, respectively. The inter-assay and intra-assay imprecision were all less than 6.58% and 10.62%, respectively. The RI of CEA and AFP was 0-3.84 ng/mL and 0-9.94 ng/mL, respectively. Regarding to clinical sample detection, no significant difference was observed between the proposed duplex assay and the ECLIA method. CONCLUSIONS: The ICP-MS-based duplex immunoassay was successfully developed and the analytical performance fully proved clinical applicability. Well, this could be different with other analytes.