Figure 1.

Flow diagram illustrating the selection of studies assessing blood-based risk-predictive and diagnostic biomarkers of colorectal cancer using pre-diagnostic samples from asymptomatic individuals, i.e., samples collected in prospective cohorts or general screening settings. During data extraction, an additional five studies were excluded due to lack of key information (n = 1), too small sample size (n = 2) or non-general screening population (n = 2). * Other sources included reference lists, review articles, the article collections of the authors and post hoc searches of PubMed.