Development of an automated chemiluminescent immunoassay for cancer antigen 72-4 and the evaluation of its analytical performance.

Objectives: Cancer antigen (CA) 72-4 assay is widely used for monitoring gastric and ovarian cancers. The antigen is a mucin-like, tumor-associated glycoprotein known as TAG-72. It has been identified and characterized using two different monoclonal antibodies, CC49 and B72.3, which recognize its glycochain epitopes, Galß(1-3) sialyl-Tn and sialyl-Tn antigens, respectively. This study describes the quantitative analytical performance of a newly developed CA 72-4 assay, ARCHITECT CA 72-4. Design: and Methods: The ARCHITECT CA 72-4 assay was developed using the ARCHITECT i2000SRs and three ARCHITECT i1000SRs. The assay performance was evaluated based on guidance from CLSI (Clinical and Laboratory Standards Institute) and correlation against Elecsys CA 72-4. Results: In the total precision study, the minimum coefficient of variation (CV) for Control/Panel samples over 4 U/mL was 1.1%. The measuring interval was from 0.95 to 200 U/mL with good linearity; and limits of blank (LoB), detection (LoD), and quantitation (LoQ) were 0.09, 0.18, and 0.95 U/mL, respectively. High dose hook effect; differences among specimen tube types; and interference of common drugs, potential cross-reactants, and endogenous substances were not observed. Significantly, this assay has high biotin tolerance at 4875 mg/mL and correlates well with the Elecys CA 72-4 assay (correlation coefficient: 0.95). Conclusions: ARCHITECT CA 72-4 is a highly sensitive and precise assay for CA 72-4 measurement in human sera and plasma.

Development and evaluation of analytical performance of a fully automated chemiluminescent immunoassay for protein induced by vitamin K absence or antagonist II.

OBJECTIVES: Protein induced by vitamin K absence or antagonist II (PIVKA-II), an abnormal form of prothrombin, has been used as an aid in the diagnosis of hepatocellular cancer (HCC) as a tumor marker. We developed a fully automated quantitative immunoassay for PIVKA-II on the ARCHITECT® i systems. The aim of this study was to evaluate the analytical performance of this assay. DESIGN AND METHOD: Assay imprecision, sensitivity, dilution linearity, high dose hook effect, sample type equivalency, assay interferences of potential interfering materials and correlation with Picolumi PIVKA-II (Eidia, Tokyo, Japan) were evaluated. RESULTS: The percentage coefficient of variation (%CV) of total imprecision ranged from 2.8% to 5.4% with 10 levels of samples. The limit of blank (LoB), limit of detection (LoD), and limit of quantitation (LoQ) were less than 0.63 mAU/mL, 1.62 mAU/mL, and 8.25 mAU/mL, respectively. Linearity up to 30,000 mAU/mL, no high dose hook effect, no difference among sample types and no interference of common drugs and endogenous substances were observed. Correlation study with the Picolumi PIVKA-II gave a correlation coefficient of 0.93 and a regression slope of 1.07. CONCLUSIONS: The results demonstrate that the fully automated prototype ARCHITECT PIVKA-II assay is an accurate, highly sensitive and precise assay for the measurement of PIVKA-II levels in human sera and plasmas.

Kenji Soda--researching enzymes with the spirit of an alpinist.

Like an alpinist continuously seeking virgin peaks to climb, Kenji Soda has investigated a variety of unique enzymes for which there was little or no information available; and by doing so he opened up a variety of new fields in enzyme science and technology. In particular, he has promoted the study of enzymes requiring vitamin B-derived cofactors such as FAD, NAD(P) and pyridoxal 5'-phosphate, shedding light on their reaction mechanisms, enzymological properties, crystal structures and potential practical applications. Highlighted in this review are the studies of enzymes acting on d-amino acids and sulphur/selenium-containing amino acids and those from thermophilic and psychrophilic bacteria.