From the Guidelines
Lactate dehydrogenase (LDH) testing should be ordered when evaluating conditions involving tissue damage or cell death, particularly in cases of suspected cancer, myocardial infarction, hemolytic anemia, liver disease, pulmonary embolism, or muscle injury. You should consider ordering an LDH test when assessing patients with certain cancers (particularly lymphomas, leukemias, testicular cancer, and melanoma) as it is useful for monitoring disease progression and treatment response, with elevated levels potentially indicating tumor burden or recurrence 1. LDH is an intracellular enzyme present in nearly all body tissues, so its elevation in the bloodstream indicates cellular damage. While once commonly used as a front-line diagnostic test, LDH has been largely replaced by more specific markers in many clinical scenarios, but it remains valuable as part of a comprehensive diagnostic panel or for monitoring certain conditions over time, with normal levels typically ranging from 140-280 U/L, though reference ranges vary by laboratory. In the context of trauma, lactate measurements are recommended to estimate and monitor the extent of bleeding and tissue hypoperfusion, with base deficit as a suitable alternative in the absence of lactate measurements 1. However, it's essential to note that LDH is not the primary test for diagnosing conditions like myocardial infarction, where more specific markers are preferred, but it can still provide valuable information when used in conjunction with other diagnostic tools. The decision to order an LDH test should be based on the clinical presentation and the potential for tissue damage or cell death, taking into account the patient's overall condition and medical history.
From the Research
When to Order a Lactate Dehydrogenase (LDH) Test
- LDH tests are typically ordered when a patient presents with symptoms of tissue damage or disease, such as cancer, as LDH is a marker of injury and disease 2, 3.
- Elevated LDH levels have been associated with poor overall survival in patients with cervical cancer 2 and small cell lung cancer 4.
- LDH tests may also be ordered to monitor treatment response in patients with inflammatory diseases, such as COVID-19, as high serum LDH levels have been linked to increased mortality 5.
- In some cases, LDH tests may be ordered to differentiate between benign and malignant diseases, although LDH elevation alone may not be sufficient for this purpose 6.
- The test may be ordered when a patient has a high risk of tumor growth or metastasis, as LDH levels can be used to monitor disease progression 3, 4.
Clinical Significance of LDH Test Results
- Elevated LDH levels can indicate tissue damage or disease, but may not be specific to a particular condition 6.
- LDH levels above 10-fold the normal rate may be associated with a poor prognosis and increased mortality 6.
- Normalization of LDH levels may indicate effective treatment, while elevated levels may suggest therapeutic failure 6.
- Variations in LDH levels over time can be used to monitor disease progression and treatment response 6, 4.