1. A computerized method of evaluating gastrointestinal cancer risk, comprising: generating a set of features comprising a plurality of current blood test results from a blood collected from a target individual; selecting at least one classifier according to at least one demographic characteristic of said target individual from a plurality of classifiers each generated according to a plurality of respective historical blood test results of a plurality of sampled individuals having at least one different demographic characteristic; said at least one classifier is generated according to an analysis of said plurality of respective historical blood test results of each of another of said plurality of sampled individuals; and evaluating, using a processor, a gastrointestinal cancer risk of said target individual by classifying said set of features using said at least one classifier; and wherein each of said plurality of historical and current blood test results comprises results of at least one the following blood tests: red blood cells (RBC), hemoglobin (HGB), and hematocrit (HCT) and at least one result of the following blood tests hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC).