Lactate can also be increased, even when there is no evidence of oxygen deprivation. Increased lactate can occur if patients have decreased activity of the enzyme pyruvate dehydrogenase or impaired clearance of lactate as a result of hepatic dysfunction.
Plasma lactate concentration can be falsely increased if the plasma is not separated from the cells shortly after sample collection (Centrifugation and separation of plasma from cells is recommended within 15 minutes of collection). Blood cells continue to metabolize glucose following collection, resulting in the production of lactic acid. For this reason, a gray-top tube containing sodium fluoride, which inhibits glycolysis, is usually recommended for plasma lactate sample collection. Other preanalytic errors that may also produce falsely increased lactate concentrations include: tourniquet usage during specimen collection combined with patient clenching and unclenching his/her fist and specimen hemolysis. It is also recommended that the blood specimen is placed on ice immediately after collection to further inhibit glycolysis and lactic acid formation.