New stool tests for colorectal cancer screening: a systematic review focusing on performance characteristics and...

New stool tests may be promising tools for future colorectal cancer (CRC) screening. The aim of this review was to summarize current evidence of performance characteristics and practicalness in a population-based screening setting of recently developed stool tests. The MEDLINE database was searched for relevant articles published until July 2004. Studies were included if they comprised more than 10 cases and more than 10 controls. Details on study population, performance characteristics and stool collection procedure were taken into account. Overall, 29 studies, mostly retrospective, were included, investigating 17 different stool markers or marker combinations. Underlying study populations were very heterogeneous and mostly very small. Half of the studies reported sensitivity for adenomas in addition to sensitivity for CRC, and fewer than half reported sensitivity by tumor stage or location. Performance characteristics of stool tests varied to a large extent. For most DNA-based markers, specificity was about 95% or higher, but sensitivity was mostly low even for invasive CRC. More studies with larger sample sizes were done for protein-based markers, which typically had lower specificity. In most studies, stool samples were frozen within a rather short time period after defecation. While promising performance characteristics have been reported for some tests, more pervasive evidence from larger, prospectively designed studies, which also consider aspects of practicalness, e.g., the possibility of mailing the samples, is needed.