Pyruvate kinase (PK) is an important enzyme in metabolism, in a process called glycolysis. Pyruvate kinase can be present in various forms – these are referred to as isoenzymes.In tumors, there is an altered metabolism because tumor cells divide much faster than healthy cells. This results in significantly more pyruvate kinase being produced in the form M2 pyruvate kinase. This isoenzyme of pyruvate kinase is normally present only in the lung. Furthermore, the M2-PK produced by the tumor is inactive, unlike the form normally present in the body. Therefore, the two forms can be clearly distinguished from each other. Using two special antibodies that are able to distinguish the physiological form of pyruvate kinase from tumor M2-PK, malignant tumors can thus be detected.
The method
A blood or stool sample is needed to perform the test. To detect tumors of the gastrointestinal tract, a stool sample is sufficient. To diagnose other cancers that may be present, a blood sample must be obtained. A blood or stool sample is required to perform the test (ELISA with monoclonal antibodies specific to the dimeric (tumor-specific) form of M2-PK). To detect tumors of the gastrointestinal tract, a stool sample is sufficient. To diagnose other tumor diseases that may be present, a blood sample must be taken. Material needed
- Stool sample or EDTA blood
Indications
| Carcinoma | Lung: Adeno-Ca | Lung: squamous cell Ca | Lung: Small cell Ca | Kidney | Stomach | Colon | Pancreas |
| Sensitivity | 70-71 % | 60-68 % | 35-50 % | 70-100 % (Robinson stage: IV – 100 %) | 58 % | 87 % | 71 % |
| Specificity | 95 % | 95 % | 95 % | 95 % | 90 % | 90 % | 90 % |
Stool examination for M2-PK
- Specificity for detection of gastrointestinal tumor is reported to be 74-95.2%, sensitivity 78-81.1%.
A meta-analysis from Germany, in which 6 studies on the M2-PK colorectal cancer test were critically evaluated, concluded that the overall sensitivity (percentage of diseased patients in whom the disease is detected by the use of the test, ie. of the M2-PK test for colorectal cancer is 78% and the specificity (probability that actually healthy individuals who do not have the disease in question are detected as healthy by the test) is in the range of 74-83%.In a further meta-analysis, 17 studies with a total of more than 11,000 asymptomatic subjects, more than 700 individuals with colorectal cancer and more than 500 individuals with polyps were comprehensively evaluated. This showed that in an overall review of the studies, the average sensitivity for colorectal carcinoma was 80.3% with a specificity of 95.2%. The high specificity with such a high sensitivity leads the authors of the meta-analysis to conclude that the test is ideally suited as a screening test for colorectal neoplasia. Another study on the M2PK test came to the following conclusion: the sensitivity of the M2PK test (cut off 4 U/L) for colon carcinoma (colorectal cancer) was 81.1%, the specificity 71.1%, the negative predictive predictive value 82.8% and the positive predictive predictive value 61.9%. For the hemoccult test, the sensitivity was 36.5%, specificity was 92.2%, negative predictive predictive value was 71.5%.and positive predictive predictive value was 73%. Notice:
- A negative quantitative fecal immunochemical test (FIT) excludes underlying colorectal carcinoma 100% and high-risk adenoma 97.8%.
- The M2-PK test may also be positive in inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease.
Benefit
If colorectal cancer is detected early, that is, at a stage when only a few layers of the intestinal wall are affected, the chances of cure are 90-100%.The M2-PK colorectal cancer test is an easy-to-perform and non-invasive test for colorectal cancer screening.In combination with an immunological test procedure to detect blood in the stool, the M2-PK colon cancer test is a useful test procedure in the context of colorectal cancer screening.If the test is positive, a colonoscopy (colonoscopy) is subsequently required.