A New Immunological Fecal Occult Blood Test for Screening of Colorectal Cancer

Abstract

We used Imunocult, a new immunological fecal occult blood test based on latex agglutination reaction. First, the influences of various technical factors on the reactivity were investigated, showing the following facts. (1) Reactivity of the fecal specimen remains stable for 4-5 days after acquisition ; the stability is increased after applied on the stick. (2) Proper amount of facal specimen should be applied on the stick, because excessive amount of stool tends to result in positive reaction. (3) The reaction time is not so strict, and a number of specimens can be examined at the same time. (4) False negative results due to the prozone phenomenon are hardly recognized.
Subsequently, fecal specimens were collected from 43 patients with colorectal cancer (37 with advanced cancer, and 6 with early cancer), 32 patients with colorectal polyps and 162 normal subjects. The positive rate was 95.3% for cancer, 31.3% for polyp, and 6.2% in the normal subjects. The sensitivity and specificity of Imunocult to cancer ware calculated at 95.3% and 93.8%, respectively ; and the predicitive value of positive test and that of ne-gative test were 80.4% and 98.7% respectively. Analysis using ROC (Receiver Operating Characterisics) - Curve demonstrated that reliability is sufficiently high when the test was performed only twice.
In conclusion, this test is suitable for screening of colorectal cancer, considering the high reliability in cancer detection, the simple operation, and the relatively low cost.