Evaluation of a Modified Enzyme Linked Immunosorbent Assay for Serum PIVKA-II Measurement

Abstract

Background:The serum des-gamma-carboxyprothrombin (protein induced by vitamin K antagonist-II, PIVKA-II) is a useful tumor marker in addition to alpha-fetoprotein for diagnosing primary hepatocellular carcinoma (HCC). In this study, we evaluated the laboratory performance of a modified ELISA method for PIVKA-II measurement adopting an automated ELISA processor in comparison with conventional manual method and investigated its diagnostic performance in patients with HCC. Methods: The laboratory performance of modified ELISA using PIVKA-II ELISA kit (Sanko Junyaku Co., Japan) was evaluated using control materials (10, 25, 500, 1,000 mAU/mL) and 208 patient samples according to the CLSI guidelines. In 93 HCC patients and 88 disease controls (30 chronic hepatitis and 58 liver cirrhosis), ROC curve, sensitivity, specificity, and positive and negative predictive values were analyzed. Results: Total and within-run CVs for middle, high and very high level samples were less than 10%, while those of low level samples were over 10% (12.6% and 11.7%, respectively). The modified ELISA showed an excellent linearity (r>0.99) and low carryover rate (-0.14%). Although the correlation between the conventional and modified ELISAs was excellent (r=0.982), there was a proportional deviation of PIVKA-II levels (y intercept: 0.621). With a cut-off of 30 mAU/mL, the sensitivity and specificity of PIVKA-II for the diagnosis of HCC were 58% and 92%, respectively. Conclusions: PIVKA-II measurement by modified ELISA using an automated ELISA processor can improve the efficiency of laboratory in terms of turnaround time and labor intensiveness while maintaining reasonable sensitivity and specificity for the diagnosis of HCC.