title: Problems encountered in the immunoassay of alpha-foetoprotein in patients with hepatoma.
abstract: Immunoradiometric assays suffer from the phenomenon of paradoxical increase in count rate with increasing dilution of highly concentrated samples--the "hook-effect". This is particularly important for alpha-foetoprotein where in hepatoma may be thousands of times the upper limit of the range of immunoradiometric assays. Using a commercial kit method we have encountered some degree of hook effect in many patients with hepatoma. Significant hooking occurred after 1,000 to 2,000 micrograms/1 but the extent of the effect was sample dependent. Of the samples tested so far, only one patient produced a hook which extended into the standard curve counts range. This resulted in a measured values of 20 micrograms/1 (value on dilution: 100,000 micrograms/1). We recommend that this method should be used routinely in conjunction with a screening method e.g., counterimmunoelectrophoresis and that quantitation of very high values should be by radial immunodiffusion or a method with similar sensitivity.
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000097:blood*; D006801:Humans; D008113:Liver Neoplasms / Q000097:blood*; D011863:Radioimmunoassay; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D000509:alpha-Fetoproteins