Effect of rehydration on guaiac-based faecal occult blood testing in colorectal cancer screening

Abstract

In the present experience rehydration doesn't produce any decrease in the positive predictive value for cancer or adenomas and the increase in the positivity rate appears quite acceptable when considering the significant increase in the detection rates of cancer and adenomas.We conclude that rehydrated HO should be introduced as the standard test for screening in order to increase sensitivity for colorectal cancer and adenomas.Screening by faecal occult blood testing has been proposed to reduce colorectal cancer incidence and/or mortality. Hemoccult II (S.K.D.) (HO), based on guaiac impregnated cards, is the most common test used worldwide.Evidence of screening efficacy is still lacking as the results of ongoing controlled studies are expected within a few years (Hardcastle et al., 1989;Kronborg et al., 1989;Mandel et al., 1988).Suboptimal estimates of sensitivity for colorectal cancer have been reported for HO, ranging from 50 to 70% (Hardcastle et al., 1989;Kronborg et al., 1989;Bertario et al., 1988;Castiglione et al., 1991). Rehydration of HO slides before development increases the sensitivity up to 85-90% (Kewenter et al., 1988)

A novel hypothesis on the sensitivity of the fecal occult blood test

“…Currently, our estimate for rehydrated FOBT in stages before the stage of clinical detection is lower than for unrehydrated FOBT. Several studies have shown that rehydration of FOBT slides increases sensitivity 10, 27-30. Rehydration of FOBT slides was mainly done in the second phase of the Minnesota trial with only follow-up screening rounds.…”

“…Several studies have shown that rehydration of FOBT slides increases sensitivity. 10,[27][28][29][30] Rehydration of FOBT slides was mainly done in the second phase of the Minnesota trial with only follow-up screening rounds. Because the modeled detection rates in follow-up rounds, and thus in this phase, are higher than observed, the estimated sensitivity for rehydrated FOBT needed to be low to compensate.…”

Diagnosing colorectal carcinoma: clinical and molecular approaches

“…Rehydration increases the cost of screening but increases the sensitivity of the test, 138,139 which raises the question of whether there are other tests for fecal blood that may enhance the specificity of the methodology and contain the cost of screening. Several recent studies suggest that immunologically based tests for human hemoglobin may enhance the sensitivity of FOBT.…”