Evaluation of an automated commercial immunoluminometric assay for alpha-foetoprotein

We evaluated a two-site immunoluminometric assay (AFP LIA-mat Byk Sangtec) for the determination of alpha-foetoprotein (AFP). The assay, involving two monoclonal antibodies which recognize two different alpha-foetoprotein epitopes, is rapid (4 h) with a wide working range (0-600 x 10(3) IU/l), a good lower limit of detection and good reproducibility (CV less than 10%). The regression equation for the AFP LIA-mat (y) and the immunoradiometric assay AFP Bridge Serono (x) was y = 1.175x - 2.27 (n = 95, r = 0.996) for serum and y = 1.16x + 479.2 for amniotic fluid. It did not display a hook effect, and when we assessed the linearity by assaying a high concentration of alpha-foetoprotein, it gave a linear response down to 3.1 x 10(3) IU/l. We also evaluated the clinical response of AFP LIA-mat in 278 patients with different diseases. Eighteen of the 19 patients with hepatocellular carcinoma had alpha-foetoprotein levels greater than 100 x 10(3) IU/l. In contrast, only 5 of the 47 patients with cirrhosis showed values above 50 x 10(3) IU/l, demonstrating that this assay discriminates fairly well between hepatocellular carcinoma and cirrhosis. Data in agreement with the literature were obtained for testicular tumours; all of seven seminomatous tumours presented values below 5 x 10(3) IU/l, whereas 50% of the non-seminomatous tumours (n = 8) presented values above 20 x 10(3) IU/l.