Evaluation of a monoclonal immunoenzymometric assay for alpha-fetoprotein

A monoclonal immunoenzymometric assay for alpha-fetoprotein was evaluated for detection and monitoring of hepatocellular carcinoma (HCC). We studied 1343 serum specimens from 759 patients with various neoplastic and non-neoplastic diseases. The interassay CV for this assay (M-AFP) ranged from 3.5 to 5.5%, with a minimum detectable concentration of 2.2 micrograms/L, as compared with 10 micrograms/L for a polyclonal (P-AFP) RIA for AFP. The calibration curve (0-300 micrograms/L) was linear, and serum dilutions paralleled it. The reference interval (0-9 micrograms/L) was established from data on 111 healthy subjects. Regression analysis of the AFP concentration (0-300 micrograms/L) of HCC patients obtained with the M-AFP assay (y) and the P-AFP RIA (x) yielded the equation y = (1.125)x - 0.52 (r = 0.9395, n = 165), with a considerable number of discrepant results for AFP less than 100 micrograms/L. By M-AFP immunoassay, AFP was above-normal (greater than 9 micrograms/L) in most HCC patients (80%), and to a lesser extent in other liver tumors (48%). AFP was within the normal reference interval for most patients with germ-cell tumors or benign liver disease and for other disease groups. For maximum diagnostic efficiency (90%) for HCC the decision level was increased to 100 micrograms of AFP per liter. Changes in serum AFP were correlated with changes in tumor volume in most HCC patients.