Quantification and utility of monosialylated alpha-fetoprotein in the diagnosis of hepatocellular carcinoma with nondiagnostic serum total alpha-fetoprotein.

Background: At concentrations <500 microg/L, serum alpha-fetoprotein (AFP) has low specificity in the diagnosis of hepatocellular carcinoma (HCC), but monosialylated AFP (msAFP) is more specific for HCC. We describe two strategies for quantitative analysis of msAFP and explore their diagnostic accuracy in cases of HCC with nondiagnostic serum total AFP concentrations.

Methods: We first used isoelectric focusing, Western blot, and densitometry (IEF-Western blot assay). We then developed a second assay, a novel glycosylation immunosorbent assay (GISA), based on the specificity of sialyltransferase and immunosorbent technology. Both assays were used to measure msAFP and msAFP percentage relative to total AFP in sera with nondiagnostic AFP concentrations from 36 patients with newly diagnosed HCC and from 18 patients with liver cirrhosis.

Results: The msAFP percentages and concentrations were significantly higher in the HCC patient group regardless of the quantification methods. The msAFP concentrations and msAFP percentages obtained by the two assays were highly correlated (r = 0.70 and 0.49, respectively). For discrimination of HCC with nondiagnostic serum total AFP from liver cirrhosis, the areas under the ROC curves were 0.81 (95% confidence interval, 0.70-0.92) for msAFP by IEF-Western blot assay, 0.73 (0.58-0.87) for msAFP by GISA, 0.89 (0.80-0.97) for msAFP percentage by IEF-Western blot assay, and 0.74 (0.59-0.89) for msAFP percentage by GISA.

Conclusions: Both the serum concentration and percentage of msAFP are potential diagnostic markers for HCC with nondiagnostic AFP. GISA can quantify a specific glycoform of a serologic marker.