Random comparison of guaiac and immunochemical fecal occult blood tests for colorectal cancer in a screening population.
OBJECTIVE
Despite poor performance, guaiac-based fecal occult blood tests (G-FOBT) are most frequently implemented for colorectal cancer screening. Immunochemical fecal occult blood tests (I-FOBT) are claimed to perform better, without randomized comparison in screening populations. Our aim was to randomly compare G-FOBT with I-FOBT in a screening population.


METHODS
We conducted a population-based study on a random sample of 20,623 individuals 50-75 years of age, randomized to either G-FOBT (Hemoccult-II) or I-FOBT (OC-Sensor). Tests and invitations were sent together. For I-FOBT, the standard cutoff of 100 ng/ml was used. Positive FOBTs were verified with colonoscopy. Advanced adenomas were defined as >or=10 mm, high-grade dysplasia, or >or=20% villous component.


RESULTS
There were 10,993 tests returned: 4836 (46.9%) G-FOBTs and 6157 (59.6%) I-FOBTs. The participation rate difference was 12.7% (P < .01). Of G-FOBTs, 117 (2.4%) were positive versus 339 (5.5%) of I-FOBTs. The positivity rate difference was 3.1% (P < .01). Cancer and advanced adenomas were found, respectively, in 11 and 48 of G-FOBTs and in 24 and 121 of I-FOBTs. Differences in positive predictive value for cancer and advanced adenomas and cancer were, respectively, 2.1% (P = .4) and -3.6% (P = .5). Differences in specificities favor G-FOBT and were, respectively, 2.3% (P < .01) and -1.3% (P < .01). Differences in intention-to-screen detection rates favor I-FOBT and were, respectively, 0.1% (P < .05) and 0.9% (P < .01).


CONCLUSIONS
The number-to-scope to find 1 cancer was comparable between the tests. However, participation and detection rates for advanced adenomas and cancer were significantly higher for I-FOBT. G-FOBT significantly underestimates the prevalence of advanced adenomas and cancer in the screening population compared with I-FOBT.
van Rossum
Leo G
LG
Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands. l.vanrossum@mdl.umcn.nl
van Rijn
Anne F
AF
Laheij
Robert J
RJ
van Oijen
Martijn G
MG
Fockens
Paul
P
van Krieken
Han H
HH
Verbeek
Andre L
AL
Jansen
Jan B
JB
Dekker
Evelien
E
D000236:Adenoma / Q000175:diagnosis* / Q000453:epidemiology; D000368:Aged; D003111:Colonic Polyps / Q000175:diagnosis / Q000453:epidemiology; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006138:Guaiac; D006801:Humans; D007150:Immunohistochemistry; D007202:Indicators and Reagents; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D009780:Occult Blood; D018579:Patient Selection; D011237:Predictive Value of Tests; D015995:Prevalence; D011446:Prospective Studies
D007202:Indicators and Reagents; D006138:Guaiac