FALSE CHANGES IN CA-125 LEVELS IN OVARIAN-CANCER PATIENTS AFTER INFUSION OF OC125 FRAGMENTS FOR DIAGNOSTIC AND THERAPEUTIC PURPOSE

The influence of human anti-OC125 antibodies formed after multiple inf usions of OC125 F(ab'), fragments on the apparent levels of CA 125 mea sured with four different tests were examined in two ovarian cancer pa tients. With the homologous Assay 1, involving only OC125 antibodies, false increases of CA 125 values were observed after infusion of OC125 fragments, which completely covered real CA 125. In contrast, with As say 2, 3 and 4, which involve no OC125 antibodies as capture antibodie s, only slight false increases occurred in the presence of very high a nti-OC125 antibody concentrations. Interference was eliminated by addi tion of non-specific murine IgG in Assay 2 and 4, but not in Assay 1 a nd 3 indicating that the false increases in Assay 1 and 3 were caused by anti-idiotypic anti-OC125 antibodies. In the presence of elevated r eal CA 125, with Assay 2 and to a considerably lesser degree with Assa y 4, an inhibitory effect of anti-OC125 antibodies became evident lead ing to false decreases of CA 125 values. In Assay 4 reduction of assay response was eliminated by addition of nonspecific murine IgG. The re sults confirm that all available CA 125 tests are influenced by interf erence with human anti-OC125 antibodies. Thus, CA 125 levels in patien ts who have been treated with OC125 fragments should be interpreted wi th care.