Determination of serum des-gamma-carboxy prothrombin levels in patients with small-sized hepatocellular carcinoma: comparison of the conventional enzyme immunoassay and two modified methods

Currently available enzyme immunoassays for des-gamma-carboxy prothrombin (DCP) are not sensitive enough to detect hepatocellular carcinoma (HCC) at an early stage. Therefore, the objectives of this study were to enhance the sensitivity of the currently available enzyme immunoassay (EIA) for DCP and to assess the diagnostic values of the new methods compared with those of alpha-fetoprotein (AFP) in patients with small-sized HCC.Coded serum samples obtained from a total of 128 patients with chronic liver diseases, including 27 patients with small-sized HCC, were analyzed. DCP levels were determined in three different ways: 1) conventional EIA, 2) the overnight method, similar to the conventional EIA but the first reaction (immunoreaction of DCP with the monoclonal antibody) was proceeded overnight, and 3) the avidin-biotin complex (ABC) method.In 27 patients with HCC (or = 3 cm in diameter), the rates of abnormal values obtained by the conventional, the overnight, and the ABC methods were 14.8, 25.9, and 29.6%, respectively. The overnight and the ABC methods comparably increased the sensitivity, whereas the ABC method gave the highest false-positive value in patients with chronic liver diseases (cirrhosis and chronic hepatitis) without HCC. The negative predictive value was 84.9% when AFP and the overnight DCP assays were combined, whereas the true positive rate by the combination assay of the ABC method for DCP and AFP (cut-off level at 200 ng/ml) was 33.3%.Two modifications of the conventional EIA for DCP comparably increased the sensitivity, but the overnight method may be of more practical value in terms of specificity and ease. The rate of detection of small-sized HCC by tumor markers alone, however, is not satisfactory even when the modified DCP and AFP measurements are combined.