, Volume 42, Issue 10, pp 2064-2071

Performance Characteristics and Comparison of Two Immunochemical and Two Guaiac Fecal Occult Blood Screening Tests for Colorectal Neoplasia

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Abstract

A new immunochemical test for stool Hb, FlexSureOBT, was compared with the immunochemical HemeSelect andguaiac Hemoccult II and Hemoccult SENSA tests. Blindeddevelopment of test cards smeared with stools having added human blood showed betteranalytical sensitivity of FlexSure OBT (0.2 ml blood/100g feces), than Hemoccult SENSA (≥0.5 ml) or HemoccultII (≥1.0 ml). All four stool tests were prepared by 403 subjects having endoscopic examinations.The guaiac tests and FlexSure OBT were easy to prepareand develop. The positivity rate of Hemoccult SENSA was8.7%, Hemoccult II 6%, FlexSure OBT 4.2%, and HemeSelect 3.4%. In this mainly asymptomatic(97%) population, 98% were free of clinicallysignificant neoplasia (five had cancers, three hadadenomas ≥1.0 cm). Sensitivity for cancers oradenomas ≥1.0 cm was similar for all tests (62.5-86%, NS) andHemoccult SENSA had the lowest specificity (92% vs95-98%, P < 0.05); but both Hemoccult II andHemoccult SENSA had significantly lower predictivepositive values (21% and 14%) than either FlexSure OBT(29%) or HemeSelect (50%) (P < 0.05). If bothHemoccult SENSA and FlexSURE OBT were positive in thesame subjects (1.7%), sensitivity for cancer or adenomas ≥1.0 cm (50%) was not significantly betterthan guaiac tests, but specificity (99.2%) andpredictive positive (57%) values were improved (P <0.05). In this population, guaiac tests were assensitive as immunochemical tests for clinically significantcolorectal neoplasia, but with significantly lowerpredictive positive values. A combination of a sensitiveguaiac test (Hemoccult SENSA) and a specificconfirmatory test for human Hb (FlexSure OBT) provided highspecificity, comparable to HemeSelect.