Automated leucocyte adherence inhibition testing in patients with colorectal cancer

This paper details our initial experiences with a semi-automated leucocyte adherence inhibition (SALAI) assay in patients with colorectal disease. Two assay systems were used. Leucocytes from blood donors and patients with different colorectal diagnoses were tested for sensitization to colorectal tumour extracts, and leucocytes from healthy blood donors were assayed with serum from blood donors or patients to determine whether the serum itself contained factors which would react with the non-sensitized leucocytes in the test system. The sensitivity of the SALAI assay using patients' leucocytes was 64%, and the specificity was 68%. Discriminant analysis did not affect the sensitivity of the assay for colorectal cancer (64%), although the specificity was increased for all patients except those with malignant disease other than colorectal cancer. The sensitivity of the SALAI assay using patients' serum was 50% but the specificity was 74%. Discriminant analysis increased the sensitivity of this assay to 80% but specificity was reduced to 61%. Thus, the SALAI assay with patients' serum, although potentially more advantageous than the assay using patients' leucocytes in the clinical setting, was less specific. Furthermore, samples from patients with early colorectal cancers were less reactive making the serum assay unsuitable for screening asymptomatic patients. The SALAI assay using patients' leucocytes, however, has a higher sensitivity than most reported variations of the assay but a slightly lower specificity. It is suggested that the SALAI assay is preferable to other methods for leucocyte adherence inhibition (LAI) testing.