Background/Aims:To compare the use of protein induced by vitamin K absence or antagonist II( PIVKA-II) measured conventionally with the ratio between PIVKA-II measured using P-11 and P-16 antibodies(NX-PVKA) and PIVKA-II measured conventionally (NX-PVKA-R) in terms of false-positive resultsfor hepatocellular carcinoma( HCC). Methodology:Subjects comprised 318 patients with chronic liver disease,including 8 patients receiving warfarin treatment, which can result in false-positive results for HCC.HCC was present in 65 patients (HCC group) and absent in 253 (non-HCC group). PIVKA-II was measuredconventionally. NX-PVKA-R was calculated as PIVKA-II/NX-PVKA. Results:Both PIVKA-II andNX-PVKA-R were significantly higher in the HCC group than in the non-HCC group (p<0.0001 each).False-positive results were seen in 9.5% of non-HCC patients with PIVKA-II, and in 10.3% with NX-PVKA-R. False-positive results were seen for all 8 patients (100%) on warfarin with PIVKA-II, but for 0%with NX-PVKA-R. Sensitivity, specificity, and accuracy were all lower for NX-PVKA-R than PIVKA-II.Conclusions:NX-PVKA-R is not more useful than PIVKA-II for diagnosing HCC, but is very useful insubpopulations such as patients on warfarin and patients with jaundice. The characteristics of NX-PVKA-Rcan be best exploited by selecting patients in which these factors are present