1. A computerized method for providing a client terminal with an evaluation of gastrointestinal cancer risk in response to an indication of current blood test results of a patient, comprising: receiving by a computing system associated with a database storing a plurality of classifiers and from a client terminal and via a network, an indication of values of a plurality of current blood test results calculated based on an analysis of a blood collected from a target individual; generating, by said computing system, a combination of at least 10 blood test features based on said plurality of current blood test results, each one of said at least 10 different blood test features is based on a blood test value of one of said plurality of current blood test results; selecting at least one classifier according to at least one demographic characteristic of said target individual from said plurality of classifiers, each of said plurality of classifiers is 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 hardware processor of said computing system, a gastrointestinal cancer risk of said target individual by classifying said combination of at least 10 different blood test features using said at least one classifier; and outputting said gastrointestinal cancer risk for presentation by said client terminal; 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); wherein said at least one classifier is generated according to each of said plurality of historical test results that individually have insufficient statistical significance correlating between said respective test result and having gastrointestinal cancer.