2001 Volume 28 Issue 4 Pages 411-421
Background A fecal occult blood test (FOBT) for screening for colonic cancer is accessible to all of health plan participants but adherence of FOBT-positive participants with recommended BE or CF is poor, which lowers the final CRC detection rate. The leading cause of poor adherence seems to be low specificity of the FOBT.
Method With a health plan performing 15, 000+multiphasic tests per year that include a 3-day method FOBT and sigmoidofiberscopy, a retrospective chart review was conducted and linked to switching of interpretation of FOBT data that markedly improved Colonic cancer detection rate more than 3 times. Blood density of stool specimens were measured with immunoassay and reported in terms of ng/ml. The patterns of three figures of blood density for each participant's stool specimens were examined in relation to the presence of cancers or adenomas as well as the timing of removals of these neoplasia.
Results Quantitative test results represented in ng/ml tell more about suspected colonic bleeders than conventional qualitative test results. Patterns of FOBT data characteristic of colonic neoplasia are as follows;
1. Continuity of positivity; In 74% and 61% of sets of 3 stool specimens of colonic cancers and adenomas respectivly, all three were positive (figures over thresholds) . Threshold values were 100 ng/ml for cancer and 30 ng/ml for adenoma.
2. Resemblance of 3 figures for blood density; In 63% of sets of 3 stool specimens of neoplasia of the colon, figures for blood density of each set closely resembled each other. Benign bleeders such as hemorrhoids and diverticuli, however, rarely showed continuity of positivity or resemblance as was noted in neoplasia. In 94% of adenoma cases, after polypectomy, all of the three figures of blood density went down to near zero, suggesting that the previous bleedings were caused by minute collision between stools and protrusions of the colonic inner surface.
Conclusion When blood densities of stool specimens are measured quantitatively in terms of ng/ml and the data thus obtained are interpreted in terms of continuity, the FOBT helps physicians distinguish colonic neoplasia from other nonprotruding colonic bleeders and raises cost-efficiency of the BEs and/or CFs they perform.