Diagnostic Validity of Fecal Occult Blood Tests for Detecting Gastroenterological Cancers

Abstract

In order to estimate the diagnostic validity of chemical fecal occult blood tests, i.e. orthotolidine (Shionogi A) and guajac (Shionogi B) slides for detecting cancers of the esophagus, stomach and colorectum, the authors followed up all the examinees (n=3,449) of comprehensive medical check‐ups at the Center for Adult Diseases, Osaka, by means of record linkage to the Osaka Cancer Registry's files. Then, diagnostic validity was calculated based on the results of two years’ follow‐up. Sensitivity for the respective cancers was 20.0%, 11.8% and 62.5% for Shionogi A, and 20.0%, 5.9% and 43.8% for Shionogi B slides. Likelihood ratio for the respective cancers was 1.4, 0.8 and 4.5 for Shionogi A, and 3.3, 1.0 and 7.5 for Shionogi B. Specificity was analogous among the three cancer sites, being 86% for Shionogi A and 94% for Shionogi B. These results suggest that the diagnostic validity of chemical occult blood tests for detecting cancers of the esophagus and the stomach is very poor, and therefore imply that close examinations of these sites for screening positives is unnecessary in mass screenings for colorectal cancer.

Effect of Verification Bias on the Sensitivity of Fecal Occult Blood Testing: a Meta-Analysis

“…The studies that attempted to reduce verification bias are listed in Table 2. [51][52][53][54][55][56][57][58][59][60] These 10 studies included 185 subjects with colorectal cancer and 31,804 controls. Seven studies reduced verification bias by performing colonoscopy on all of the potential subjects 51,54-56,58-60 while 3 studies used longitudinal follow-up for at least 2 years.…”

“…Seven studies reduced verification bias by performing colonoscopy on all of the potential subjects 51,54-56,58-60 while 3 studies used longitudinal follow-up for at least 2 years. 52,53,57 All of the 10 studies specified that the specimens were collected at home. Tables 3 and 4 include studies that evaluated more sensitive chemical-FOBT tests either by adding an enhancer (e.g., Hemoccult® SENSA®), re-hydration of the specimen card, or using toluidine instead of guaiac.…”

“…Table 4 51, 53,57,[64][65][66] includes the studies that attempted to correct for verification bias either by colonoscopy of all subjects regardless of FOBT status 51,65 or longitudinal follow-up of subjects who did not undergo colonoscopy. 53,57,64,66 Sensitivity and Specificity of Standard Guaiac-Based FOBT Paired forest plots displaying the sensitivities and specificities of studies with and without verification bias are shown in…”