Epitope characterization of an anti-PIVKA-II antibody and evaluation of a fully automated chemiluminescent immunoassay for PIVKA-II

Performance evaluation of serum PIVKA-II measurement using HISCL-5000 and a method comparison of HISCL-5000, LUMIPULSE G1200, and ARCHITECT i2000

Background

Protein induced by vitamin K antagonist‐II (PIVKA‐II), in addition to alpha‐fetoprotein, is a useful tumor marker for diagnosis of hepatocellular carcinoma (HCC). We evaluated the analytical performance of the HISCL‐5000 analyzer (Sysmex Corporation) in the measurement of serum PIVKA‐II.

Methods

We evaluated the precision and linearity of PIVKA‐II assays using the HISCL‐5000 analyzer. Methods using HISCL‐5000, LUMIPULSE G1200 (Fujirebio Diagnostics), and ARCHITECT i2000 (Abbott Diagnostics) were compared according to the guidelines of the Clinical and Laboratory Standards Institute. A total of 501 subjects (median age 59 years, age range 24‐90 years) were enrolled. Among them, 335 were HCC patients, 46 were patients with non‐HCC liver disease, and 120 were healthy individuals. Non‐HCC liver disease included liver cirrhosis, chronic hepatitis, HBV or HCV carrier, hepatic adenoma, and intrahepatic cholangiocarcinoma.

Results

Repeatability (%CV) in low‐ and high‐level controls and pooled serum was 2.81%‐10.30%, and within‐laboratory precision was 4.24%‐8.86%. In a linearity test, the coefficient of determination (R²) was 0.9957, ranging from 11 to 69 897 mAU/mL. In comparison, the coefficient of correlation (r) was 0.9561‐0.9644, agreement was 93.4%‐97.6%, and the κ value was 0.855‐0.945 among the three analyzers. About 99.2% of healthy individuals and 84.8% of non‐HCC liver disease patients were below the cutoff value (40 mAU/mL) on HISCL‐5000.

Conclusions

A PIVKA‐II assay using HISCL‐5000 showed acceptable analytical performance including precision, linearity, and method comparison. This indicates that HISCL‐5000 can be potentially helpful in clinical laboratories.

Serum ARCHITECT PIVKA-II reference interval in healthy Chinese adults: Sub-analysis from a prospective multicenter study

BACKGROUND

Protein induced by vitamin K absence or antagonist-II (PIVKA-II) has been widely used as a biomarker for liver cancer diagnosis in Japan for decades. However, the reference intervals for serum ARCHITECT PIVKA-II have not been established in the Chinese population. Thus, this study aimed to measure serum PIVKA-II levels in healthy Chinese subjects.

METHODS

This is a sub-analysis from the prospective, cross-sectional and multicenter study (ClinicalTrials.gov Identifier: NCT03047603). A total of 892 healthy participants (777 Han and 115 Uygur) with complete health checkup results were recruited from 7 regional centers in China. Serum PIVKA-II level was measured by ARCHITECT immunoassay. All 95% reference ranges were estimated by nonparametric method.

RESULTS

The distribution of PIVKA-II values showed significant difference with ethnicity and sex, but not age. The 95% reference range of PIVKA-II was 13.62-40.38 mAU/ml in Han Chinese subjects and 15.16-53.74 mAU/ml in Uygur subjects. PIVKA-II level was significantly higher in males than in females (P < 0.001). The 95% reference range of PIVKA-II was 15.39-42.01 mAU/ml in Han males while 11.96-39.13 mAU/ml in Han females.

CONCLUSIONS

The reference interval of serum PIVKA-II on the Architect platform was established in healthy Chinese adults. This will be valuable for future clinical and laboratory studies performed using the Architect analyzer. Different ethnic backgrounds and analytical methods underline the need for redefining the reference interval of analytes such as PIVKA-II, in central laboratories in different countries.

Myeloma-Derived Light Chain Paired with a Diagnostic Monoclonal Antibody Hinders Immunoassay Performance

Monoclonal antibodies are widely used as the capture and detection reagents in diagnostic immunoassays. In the past, myeloma fusion partners expressing endogenous heavy and/or light chains were often used to generate hybridoma cell lines. As a result, mixed populations of antibodies were produced that can cause inaccurate test results, poor antibody stability, and significant lot-to-lot variability. We describe one such scenario where the P3U1 (P3X63Ag8U.1) myeloma fusion partner was used in the generation of a hybridoma producing protein induced vitamin K absence/antagonist-II (PIVKA II) antibody. The hybridoma produces three subpopulations of immunoglobulin as determined by ion exchange (IEx) chromatography that exhibit varying degrees of immunoreactivity (0%, 50%, or 100%) to the target antigen as determined by Surface Plasmon Resonance. To produce an antibody with the highest possible sensitivity and specificity, the antigen-specific heavy and light chain variable domains (VH and VL) were cloned from the hybridoma and tethered to murine IgG1 and kappa scaffolds. The resulting recombinant antibody was expressed in Chinese hamster ovary cells and is compatible for use in a diagnostic immunoassay.

A quantitative analytical method for PIVKA-II using multiple reaction monitoring-mass spectrometry for early diagnosis of hepatocellular carcinoma

Prothrombin induced by vitamin K absence-II (PIVKA-II) is an effective tumor marker for hepatocellular carcinoma (HCC). We have developed a novel targeted mass spectrometric (MS) assay for quantifying PIVKA-II in human serum. The ideal signature peptide was selected to measure PIVKA-II concentrations on a triple quadrupole (QqQ) mass spectrometer, and the chromatography gradient was optimized for the peptide separation to minimize elution interference. Using multiple reaction monitoring-mass spectrometry (MRM-MS), good linearity (R ² = 0.9988) was obtained for PIVKA-II over a range of 3 orders. We achieved a limit of detection (LOD) of 0.45 nM (31.72 ng/mL), a limit of quantification (LOQ) of 0.93 nM (65.31 ng/mL), a lower limit of quantification (LLOQ) of 0.49 nM (34.32 ng/mL), and an upper limit of quantification (ULOQ) of 1000.00 nM (70,037.00 ng/mL). The intra-day and inter-day precisions were within ±14.96%, and the accuracy ranged from 87.66 to 114.29% for QC samples at four concentrations. Compared with an established immunoassay, the correlation (R = 0.8335) was good for the measurements of PIVKA-II concentrations. This method was successfully applied to the analysis of clinical samples for normal control (n = 50), chronic hepatitis (n = 50), liver cirrhosis (n = 50), HCC (n = 50), and recovery (n = 50) serum. Graphical Abstract MRM-MS assay development for determining concentration of PIVKA-II in serum and a comparison between MRM-MS assay and immunoassay with high correlation.

Diagnostic accuracy of des-gamma-carboxy prothrombin for hepatocellular carcinoma in a French cohort using the Lumipulse® G600 analyzer

The increasing incidence of hepatocellular carcinoma (HCC) in Western countries requests reliable tumour markers for preclinical diagnosis. We evaluated the diagnostic accuracy of des-gamma-carboxy prothrombin (DCP), in comparison with alpha-fetoprotein (AFP) in a French cohort using a new analyser. One hundred and sixty-two patients with virus-related cirrhosis (46 HCC patients and 116 controls) were recruited in this retrospective proof-of-concept study. DCP was measured on new Lumipulse^® G600 analyzer and AFP on usual Cobas e602 analyzer in serum samples that were collected at the time of HCC diagnosis for HCC patients or during follow-up for controls. DCP and AFP levels were higher in HCC patients. The area under receiver operating characteristic curve was larger for DCP than for AFP (0.89 vs 0.77, P=.03). At the cut-off value of 128 mAU/mL, sensitivity and specificity for DCP were 74% and 92%. At the cut-off value of 20 μg/L, sensitivity and specificity for AFP were 63% and 82%. NRI_>0 for the association of "AFP+DCP" were 101%, P<.0001, and 23%, P=.03, compared to "AFP" or "DCP" alone, respectively. We conclude that DCP outperformed AFP for the detection of HCC.