From the Guidelines
When ordering a Lactate Dehydrogenase (LDH) test, I expect to receive a measurement of this enzyme's activity in the blood, reported in units per liter (U/L), which can indicate tissue damage or cell death, and is useful for monitoring various conditions, including cancers, particularly in the context of testicular cancer and lymphomas, as supported by recent guidelines 1.
Key Points to Consider
- Normal adult reference ranges for LDH typically fall between 140-280 U/L, though exact ranges vary by laboratory.
- Elevated LDH levels are non-specific but can indicate tissue damage or cell death, making it a valuable marker for conditions like myocardial infarction, hemolysis, liver disease, and muscle disorders.
- LDH is particularly useful in the prognosis and monitoring of testicular cancer and lymphomas, as well as in assessing the severity of disease in melanoma patients, where elevated LDH levels are associated with worse survival outcomes 1.
- The test requires a standard blood draw, with no special preparation needed from the patient, and results are usually available within 24 hours.
- When interpreting results, it's crucial to consider the clinical context and potentially order LDH isoenzyme testing to determine which specific tissues are affected, given that LDH exists in five different forms distributed differently throughout body tissues.
Clinical Utility and Limitations
- LDH has shown prognostic value for patients with advanced disease, particularly in melanoma, where it is incorporated into the AJCC staging system 1.
- However, for clinically localized diseases, such as renal neoplasms, the routine use of LDH measurements for follow-up is not recommended due to lack of evidence demonstrating its benefit in improving detection of metastasis 1.
- The utility of LDH in monitoring and prognosis highlights the importance of considering the clinical context in which the test is ordered, emphasizing a personalized approach to patient care.
From the Research
Expected Outcomes When Ordering LDH
When ordering Lactate Dehydrogenase (LDH) tests, several outcomes can be expected based on the context of the test. The following points highlight what can be anticipated:
- Prognostic Factor: LDH levels may serve as a significant prognostic factor in various cancers, including hepatocellular carcinoma (HCC) 2. High LDH serum levels have been associated with a poorer outcome in patients with HCC.
- Immune Suppression: Elevated LDH can indicate immune suppression in cancer, allowing neoplastic cells to evade the immune system by altering the tumor microenvironment 3. This suggests that high LDH levels might be linked to a more aggressive disease course.
- Resistance to Immunotherapy: High serum LDH and liver metastases have been identified as dominant predictors of primary cancer resistance to anti-PD(L)1 immunotherapy 4. Patients with elevated LDH and liver metastases tend to have a poorer response to immunotherapy.
- Therapeutic Target: LDH has been proposed as a target for therapy in acute liver failure 5. Inhibiting LDH can reduce liver damage and improve survival in experimental models of acute liver failure.
- Metabolic Rewiring: Inhibition of LDH in tumors can lead to rapid in vivo metabolic rewiring, making tumors vulnerable to combination therapy 6. This suggests that LDH inhibition could be a useful strategy in cancer treatment, especially when combined with other therapies.
Clinical Implications
The clinical implications of ordering LDH tests include:
- Cancer Prognosis: LDH levels can provide valuable information about the prognosis of patients with certain types of cancer.
- Immunotherapy Response: LDH levels can help predict the response to immunotherapy in patients with cancer.
- Therapeutic Strategies: LDH inhibition may offer a new therapeutic strategy for treating acute liver failure and certain types of cancer.
- Combination Therapy: LDH inhibition can be used in combination with other therapies to enhance treatment efficacy.