From the Guidelines
LDH testing should be ordered in patients with symptoms of metastasis or in the staging and surveillance of stage IV melanoma, as elevated LDH levels are associated with worse survival and may predict response to therapy in stage IV patients 1. When considering LDH testing, it's essential to evaluate the clinical context, as this test is not recommended at baseline or for surveillance in patients with lower stages of disease (stage I-III) due to its lack of sensitivity and specificity for detecting metastasis 1. In the management of cutaneous melanoma, laboratory or imaging studies, including LDH, are only recommended to evaluate signs or symptoms of metastasis, with a focus on collaboration with medical oncology for patients with higher-risk disease 1. For other conditions, such as diffuse large B-cell lymphoma, LDH is a significant factor, with elevated levels being one of the criteria for prophylaxis, especially in patients with high-risk features 1. It's crucial to interpret LDH results in the context of other clinical findings and laboratory tests, as it is a nonspecific marker that can be elevated in various conditions involving tissue damage or cellular destruction. The decision to order LDH testing should be based on the individual patient's risk factors, symptoms, and disease stage, prioritizing its use in scenarios where it can significantly impact morbidity, mortality, and quality of life. Key points to consider when ordering LDH include:
- Normal values typically range from 140-280 U/L, though reference ranges may vary by laboratory
- Blood samples should be collected carefully to avoid hemolysis, which can falsely elevate results
- LDH is a sensitive but nonspecific indicator of tissue injury across multiple organ systems
- Elevated LDH levels are associated with worse survival in stage IV melanoma and may predict response to therapy in these patients 1.
From the Research
LDH Ordering Guidelines
The decision to order Lactate Dehydrogenase (LDH) tests is typically guided by specific clinical scenarios, particularly in the diagnosis of myocardial infarction (MI) and other conditions. Key points to consider include:
- Myocardial Infarction Diagnosis: LDH isoenzymes, especially LDH-1, have been found to be useful in diagnosing myocardial infarction 2, 3. The efficiency of LDH-1 in discriminating between patients with and without myocardial infarction is notable, especially when total LDH levels are slightly to moderately elevated.
- Comparison with Other Biomarkers: Studies have shown that LDH-1 can be as efficient as CK-MB in diagnosing MI, particularly in certain time frames after the onset of symptoms 2. However, the use of LDH isoenzymes should be supplemental to other tests like creatine kinase (CK) and CK-MB.
- Cost and Utilization: There is an emphasis on reducing unnecessary laboratory tests to cut costs. LDH isoenzymes were found to be ordered routinely, even when not necessary, highlighting the need for more judicious use of these tests 4.
- Specificity and Sensitivity: The absolute value of LDH-1 above 90 U/L has been identified as the most efficient factor for diagnosing acute myocardial infarction, especially in patients with slight to moderate elevation of total serum LDH values 3.
Clinical Scenarios for LDH Ordering
LDH tests are particularly relevant in the following scenarios:
- Suspected Myocardial Infarction: When diagnosing MI, especially if other biomarkers like CK-MB are not readily available or if there's a need for supplemental diagnostic information.
- Monitoring of Known Conditions: In patients with known myocardial infarction or other conditions where LDH levels can provide valuable information on disease progression or response to treatment.
- Differential Diagnosis: In cases where differentiation between myocardial infarction and other conditions like pulmonary embolism is necessary, although other biomarkers like troponin and D-dimer are more commonly used for this purpose 5, 6.