The Prevention of Development of Colorectal Cancer by Colonoscopy after Positive Fecal Occult Blood Test
Rakchob T, MD1, Supsamutchai C, MD2, Teerapradith J, MD2, Promboon T, MD2, Chiemsombat P, MD2, Choikrua P, BSc3, Jirasiritham J, MD2
Affiliation : 1 Department of Surgery, Buriram Hospital, Buriram, Thailand 2 Department of Surgery, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand 3 Surgical Research Unit, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
Background : Fecal occult blood tests (FOBTs) have been known as a colorectal cancer (CRC) screening tool for 30 years. Because
of the reasonable price and simplicity, the test is used to the present. However, fecal occult blood tests have low specificity to the
human blood and colonoscopy is superior in colorectal cancer screening. Now, the use of fecal occult blood tests as screening tool
has been questioned.
Objective : To demonstrate that FOBTs have a role in improving diagnostic performance in colorectal cancer screening.
Materials and Methods : Retrospective chart review of patients who were screening for colorectal cancer by FOBT and colonoscopy
was performed from January 2006 to December 2015 in Ramathibodi Hospital. Patients with a history of CRC, incomplete
colonoscopy and inflammatory bowel disease were excluded. Result of FOBT and colonoscopy were collected including pathological
finding, size and location of the lesion.
Results : 2,043 patients were included in this study. FOBT positive rate was 48.89% and cancer was found in this group 99 of 999
patients (9.9%). Positive predictive value (PPV), negative predictive value (NPV) and sensitivity of positive FOBTs for the cancer
were 10 (8.2 to 12), 98.3 (97.3 to 99) and 84.6% (76.8 to 90.6), respectively. Positive predictive value (PPV), negative predictive
value (NPV) and sensitivity of positive FOBTs for advanced adenoma and cancer were 12.5 (10.5 to 14.7), 96.6 (95.4 to 97.7) and
78.1% (70.9 to 84.3), respectively. Sensitivity was increased with the larger size and number of polyps; moreover sensitivity was
highest in the left side colon (53.6%).
Conclusion : In our study showed positive FOBTs has high sensitivity for colorectal cancer screening (84.6%) with acceptable PPV
(10). With the advantage of the FOBTs, non-invasive, low cost and easy-to-used method, FOBTs should be considered for first step
CRC screening. However, the high false positive rate of this test must be made aware.
Keywords : Colorectal cancer screening, Colorectal polyp, Fecal occult blood test
