Screening an asymptomatic population for colorectal cancer

Screening for colorectal cancer using the faecal occult blood test: a critical literature review

Colorectal cancer (CRC) is a major health problem whose outcome is crucially dependent on the stage of disease at the time of diagnosis. Consequently, early detection of CRC by mass population screening is the subject of much international research and debate. A critical literature review was undertaken to determine the effectiveness of faecal occult blood (FOB) testing in CRC screening. Four issues were addressed: an appraisal of available FOB tests, their impact on CRC mortality, the appropriate screening interval and the factors influencing public compliance with FOB screening. A computerized literature search was conducted, supplemented by cross-referencing and hand searching. Forty studies which fulfilled pre-defined inclusion and exclusion criteria were appraised. A thorough assessment of methodology, combined with an applied hierarchy of evidence, resulted in the selection of 22 studies for review. The evidence from this review is that no single (currently used) FOB test provides optimal screening performance, that biennial FOB screening reduces CRC mortality by between 6-18%, that there is a small advantage in annual screening and that better dissemination of information can improve compliance rates. An appreciation of the current evidence and issues surrounding CRC screening is important to nurses in their capacity as health promoters and educators. Definitive answers to many important questions regarding FOB screening for CRC do not currently exist. Before the concept of a national screening programme could be supported, further research is needed, the key elements of which must include the assessment of more sensitive and specific FOB tests and the promotion of population compliance.