 Increased stool (fecal) levels are being investigated as a method of screening for colorectal tumors, and EDTA plasma levels are undergoing testing for possible application in the follow-up of various cancers.Sandwich ELISAs based on two monoclonal antibodies which specifically recognize Tumor M2-PK (the dimeric form of M2-PK) are available for the quantification of Tumor M2-PK in stool and EDTA-plasma samples respectively.As a biomarker, the amount of Tumor M2-PK in stool and EDTA-plasma reflects the specific metabolic status of the tumors.