Invalid Blood Results Due to Glycolysis
The significance of laboratory test results is only as good as the sample that is being tested. For this reason, there are multiple rules on how to collect and transport a sample from the patient to the laboratory analyzer. Glycolysis reduces the available glucose in the blood and causes other changes that affect the results.
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Glycolysis
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Glycolysis is the metabolic use of glucose (sugar) for energy by living cells. It takes place in the mitochondria within cells through a complex system of enzyme-mediated reactions. The intermediate byproducts of glucose include pyruvic acid and lactic acid. Also, any chemical or cold temperature interference in one of the steps of glycolysis halts all the other subsequent steps.
Serum Glucose
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Serum glucose measurements are done to make sure that the body is properly storing away excess glucose in the blood. Levels too high or too low are indicative of a metabolic disorder. If the blood sample is left sitting at room temperature, the millions of red and white blood cells in the sample continue to use glucose. As a result, the serum glucose measurement will be falsely decreased.
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Blood pH
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Blood pH, a measurement of acidity of the blood, is critical in patients with respiratory or metabolic disorders. This is because blood pH must be kept within a narrow range. Any deviation from that range may result in serious damage to the patient. Blood samples for pH measurements must be placed on ice immediately after collection. Furthermore, the test must be performed immediately. If the sample is not placed on ice or tested immediately, the continued glycolysis from cells in the sample creates acids that will lower the pH measurement, making it seem as if the blood is more acidic than it truly is.
Lactic Acid
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One of the major functions of the liver is to process lactic acid (a byproduct of anaerobic glycolysis such as that experienced during strenuous exercise) into glucose for use by the muscles. Serum lactic acid levels increase dramatically with liver failure, so the lactic acid test is performed. If glycolysis is allowed to continue within the sample, the resulting elevation in lactic acid may give physicians the impression that liver failure is occurring, if it is not, or that it is worse than it truly is.
Expert Insight
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Medical technologists and laboratory technicians are trained to prevent the effects of glycolysis and thus prevent poor lab samples from being processed. Any and all laboratory samples are refrigerated if they cannot be processed immediately. In the case of samples where the cells are not separated from the serum (the liquid portion of blood after a clot is formed), the serum is decanted into its own container to prevent cells from affecting the serum's chemistry. If a sample for pH testing is collected, it is only accepted if it is on ice and delivered within a reasonable amount of time. Finally, certain additives such as fluoride are added to samples to halt glycolysis as soon as the sample is collected. This is critical in testing the level of lactic acid and other products of glycolysis in the blood.
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