The semiquantitated immunochemical fecal occult blood test (I-FOBT) used for colorectal cancer (CRC) screening has had its long-term performance characteristics determined by clinical follow-up or sometimes by colonoscopy as the ‘gold standard’. We reanalyzed a file of total colonoscopy patients who also prepared three I-FOBTs, processed by the OC-MICRO instrument, using at least 50 ng Hb/ml buffer threshold to determine a positive test. The performance of both tests was evaluated by the National Cancer Registry follow-up to identify new CRCs and by determining the effects of the number of tests prepared and their thresholds for analysis, sex, and age on results. A total of 1630 patients, mean age 62.7 years, SD 11.9, 50.1% men, having undergone both tests were followed up for a mean of 51.5 months, SD 13.4; 25 CRC patients were registered. At 36 months, I-FOBT sensitivity for CRC was 95.8% (95% confidence interval 87.8, 104), as was initial colonoscopy; within 48 months, it was 92% (95% confidence interval 81.4, 103) and 96%, respectively. I-FOBT identified 70 of the 122 (57.2%) colonoscopy-detected advanced adenoma patients. CRC and advanced adenomatous polyps were more common in men (P<0.01), whose risk increased at 51–73 years (odds ratio 4.639, P=0.056), but not among women (odds ratio 1.952). It then increased significantly (P<0.01) for both sexes aged at least 74 years. I-FOBTs identified most CRCs diagnosed within 36 months of follow-up with sensitivity similar to that of initial colonoscopy, with neither test identifying every CRC patient. Sex and age influence results and need consideration when planning population screening.
aDepartment of Gastroenterology, Tel Aviv Medical Center
bTel Aviv University Medical School
cSchool of Public Health, Haifa University, Israel
dIsrael National Cancer Registry, Ministry of Health, Jerusalem
Correspondence to Professor Paul Rozen, MBBS, Director, Sestopali Fund for Gastrointestinal Cancer Prevention, Department of Gastroenterology, Tel Aviv Medical Center, 6 Weizmann Street, Tel Aviv 64239, Israel Tel: +972 3 6955833; fax: +972 3 6959 528; e-mail: firstname.lastname@example.org
Received July 3, 2011
Accepted August 20, 2011