Carbohydrate-based measurements on alpha-fetoprotein in the early diagnosis of hepatocellular carcinoma.

Serum alpha-fetoprotein (AFP) is a useful marker for the diagnosis of hepatocellular carcinoma (HCC), although this protein also increases moderately in benign liver diseases. The serum concentration of AFP in HCC at the time of initial diagnosis is now lower than before because of advancements in techniques for imaging the liver. The AFP concentration alone cannot distinguish between HCC and benign liver diseases, especially when it is less than 1000 ng ml-1. These circumstances lead to the need to discriminate between these diseases. This has been achieved by determining the carbohydrate structures of AFP by its reactivity with Lens culinaris agglutinin (LCA). The percentage of LCA-reactive species of AFP is significantly higher in HCC than in benign liver diseases. The fucosylation of the sugar chain at the innermost N-acetylglucosamine is the molecular basis of this variation. Therefore, the term 'fucosylation index' has been introduced to express the percentage of LCA-reactive species of AFP. This index is useful for the diagnosis of HCC even if the carcinoma is at an early stage. Furthermore, it can predict the development of HCC in the follow-up of chronic liver diseases. Thus, the qualitative and quantitative measurements of carbohydrate in AFP provide us with very valuable information for the differential diagnosis of various liver diseases.