Many participants in fecal occult blood test population screening have a higher-than-average risk for colorectal cancer.

OBJECTIVES: Population-based colorectal cancer screening by fecal occult blood testing reduces cancer-specific mortality. Current guidelines recommend this strategy for average risk individuals. This study investigated the prevalence of higher-than-average risk characteristics, and rate of prior colonoscopy, in participants in fecal occult blood test screening programs.

METHODS: Randomly selected individuals aged 50-74 years in urban Adelaide were offered free fecal occult blood test screening by mail, without prior knowledge of their medical status. Each invitation included a questionnaire to record the prevalence of higher-than-average risk characteristics related to symptoms, family history or comorbidity, as well as prior colonoscopy. The definition of average risk was taken from updated guidelines published by the US Multisociety Task Force on Colorectal Cancer.

RESULTS: Of 2538 responses analyzed, 425 individuals had had a colonoscopy within the last 5 years, 106 fulfilled family history criteria for an initial screening colonoscopy, 209 had past polyps and 26 had had colorectal cancer. Eighty-three reported recent rectal bleeding. By current guidelines, 23% of the screened population did not warrant fecal occult blood test, because either prior colonoscopy rendered it unnecessary or particular patient characteristics made colonoscopy a more appropriate initial investigation.

CONCLUSIONS: Fecal occult blood test screening programs capture a sizeable number of higher-than-average risk individuals that may warrant colonoscopic rather than fecal occult blood test screening. Other participants have had a recent colonoscopy and probably warrant a delay in screening. Mass population fecal occult blood test-based screening programs need to more effectively target those at average risk and should divert those of higher or lower risk to more individualized assessment.