From the Research
No, lactate dehydrogenase (LDH) and serum lactate are not the same laboratory test. LDH is an enzyme found in many tissues throughout the body that catalyzes the conversion between lactate and pyruvate, while serum lactate measures the actual concentration of lactic acid in the blood. According to a recent study published in 2022 1, LDH is a marker enzyme that predicts mortality in many conditions, including ARDS, serious COVID-19, and cancer patients. On the other hand, serum lactate is primarily used to assess for tissue hypoxia, sepsis, or metabolic disturbances, as lactate accumulates when oxygen delivery to tissues is inadequate.
Key differences between LDH and serum lactate
- LDH is an enzyme that catalyzes the conversion between lactate and pyruvate, while serum lactate measures the actual concentration of lactic acid in the blood.
- LDH is typically ordered to evaluate for tissue damage in various organs, including the heart, liver, muscles, lungs, and red blood cells, with elevated levels indicating cellular damage or death.
- Serum lactate is primarily used to assess for tissue hypoxia, sepsis, or metabolic disturbances, as lactate accumulates when oxygen delivery to tissues is inadequate.
- The normal range for LDH is typically 140-280 U/L, while normal serum lactate is generally 0.5-2.2 mmol/L.
Clinical significance of LDH and serum lactate
- Both LDH and serum lactate are suggested as risk factors for mortality in patients with serious inflammatory diseases, as reported in a study published in 2022 1.
- A study published in 2020 2 found that a normal lactate level alone should not be used to exclude life-threatening sepsis, and patients with metabolic acidosis characterized by low bicarbonate or high anion gap levels, but with normal lactate levels, have high rates of ICU requirement and mortality.
- LDH is an important diagnostic biomarker for some common diseases, including cancer, thyroid disorders, and tuberculosis, as reported in a study published in 2020 3.
Recommendation
LDH and serum lactate should be used as complementary tests to provide a comprehensive understanding of a patient's metabolic status, as they measure different aspects of metabolism and are ordered in different clinical scenarios.