The cancer recognition (CARE) antibody test

Abstract

The cancer recognition (CARE) antibody (Ab) test is a serologic assay for a specific IgM that is elevated in cancer patients. All tests are measured using an indirect enzyme-linked immunosorbent assay (ELISA) of human serum. The target polypeptide in the CARE Ab test is the IgM binding epitope (LT-11) of the CARE antigen (Ag) consisting of a 16 mer structure that has been produced synthetically. The mean relative concentration (MRC) is determined relative to standard, normalized human plasma. Non-parametric analysis showed median MRC values of healthy volunteers (HVs) with no history of cancer ( n=47), family history of cancer ( n=126) and a previous cancer history ( n=24) to be 26, 34 and 46, respectively. It was determined that there was no significance found among the medians of the three HV groups ( P=0.53). The specificity of the HV types was between 87 and 98%. Benign/non-cancer surgical patients ( n=27) had a median value of 20 with a specificity of 96%. The cancer patients ( n=61) had a median value of 246 with a sensitivity of 89%. There was a significant difference between the HV and cancer patients ( P<0.0001) as well as between the benign/surgical non-cancerous group and cancer patients ( P<0.0001). The IgM antibody is heat stable at room temperature for two days versus being frozen at −80°C ( r 2=0.97). Either serum or plasma samples may be used in the CARE Ab test ( r 2=0.92). The CARE Ab was almost exclusively IgM with no serum conversion to IgG in sequential measurements of patients with cancer over a six-month period. Preliminary data from patients undergoing post-operative cancer treatment showed that decreasing Ab levels revealed patients negative for residual cancer or undergoing remission, while relapsing patients show an increase in Ab levels. A return to a positive Ab level shortly after treatment is a poor prognostic sign while in advanced cancers the Ab levels may be depressed significantly.