The Diagnostic Accuracy of the M2 Pyruvate Kinase Quick Stool Test – A Rapid Office Based Assay Test for the Detection of Colorectal Cancer, PLOS ONE, 2015

Scientific Paper

Stool tests that have been widely used in the detection and screening of colorectal cancer (CRC) are based on the testing for occult blood in stools. The guaic based tests have been in use for along time but suffers from the drawback of a high false positive result due to the inherent nature of the test which depends on the oxidative capacity of the guaic substrate. In general the guaic-based fecal occult tests have limited sensitivity and specificity. In one study,the sensitivity of guaiac-based test (HemoccultSensa) was 79.4% and the specificity was 86.7%. The guiac test is inconvenient to perform as patients have to go on a restricted diet several days before the test which includes avoiding various types of food that may cause a false peroxidase reaction or are antioxidants, as well as NSAIDs and aspirin. These problems have been overcome by the newer fecal Immunochemical test (FIT) which detects the globin moiety of human hemoglobin. Globin which arises from upper GI tract is rapidly degraded by digestive enzymes. Therefore these test are highly selective for occult bleeding of colorectal in origin. The sensitivity of FIT for detection of CRC is about 70–90%. M2-pyruvate kinase (M2-PK) is an isoenzyme of pyruvate kinase, which is a key enzyme in glycolysis where it catalyzes the conversion of phosphoenolpyruvate to pyruvate. This isoenzyme is generally a highly active, tetrameric form. However in tumor tissue, on exposure to oncoproteins, M2-PK is converted into a less active dimeric form, a change which is necessary for tumor metabolism. M2-PK is not specific for any tumour and has been reported to be found in various cancers including kidney, esophageal, gastric, pancreatic, colorectal, lung, ovarian and breast cancer. M2-PK has been found in blood and stool in various cancers and thus been used in cancer screening or detection and follow-up to detect recurrence.

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[Gastrointestinal Tract (GIT). Large Intestine. Colon. Colorectal Cancer. Diagnostics. Stool Test. M2PK Assay.]