Measurement of serum levels of des-γ-carboxy prothrombin in patients with hepatocellular carcinoma by a revised enzyme immunoassay kit with increased sensitivity

Abstract

BACKGROUND. Des-γ-carboxy prothrombin (DCP) is a useful tumor marker for hepatocellular carcinoma (HCC). The conventional enzyme immunoassay (EIA) kit for DCP lacks adequate sensitivity to detect small HCC. Thus, a revised EIA kit for DCP has been developed. In this revised DCP kit, the blank value has been reduced, making it now possible to obtain a normal value. The authors used this revised EIA kit for DCP with increased sensitivity and evaluated its usefulness as a tumor marker for HCC. METHODS. Serum DCP and α-fetoprotein (AFP) levels were determined in 60 patients with HCC, 60 with cirrhosis, 57 with chronic hepatitis, and 273 normal subjects. The cutoff value for the revised DCP kit was determined to be 40 mAU/ mL, and the values for the conventional DCP kit and AFP were 100 mAU/mL (0.1 AU/mL) and 20 ng/mL, respectively. RESULTS. The mean DCP value was 17.5 mAU/mL in the normal subjects; and the detection limit was 10 mAU/mL for this revised DCP kit. The positivity rate for DCP in patients with HCC was 60% by the revised DCP kit, in contrast to 40% by the conventional DCP kit. The sensitivity, specificity, and accuracy of the revised kit were 60%, 92.3%, and 81.4%, respectively, whereas those of the conventional kit were 40%, 98.3%, and 78.5%. Thirty-five percent of HCC tumors smaller than 2 cm and 78.1% of those larger than 3 cm were positive for DCP by the revised kit. The corresponding figures were 20% and 56.3% with the conventional kit. Twelve (33.3%) of the 36 HCC patients who were negative for DCP by the conventional kit were positive by the revised kit. When the revised DCP kit was used in combination with AFP, 86.7% of the HCC patients and 78.3% of the patients with solitary HCC were positive for at least 1 of these markers. CONCLUSIONS. The revised DCP kit is more useful than the conventional DCP kit as a tumor marker for HCC and should be used in combination with AFP.