What is lactate dehydrogenase (LDH) used for?

Diagnostic and Prognostic Applications of Lactate Dehydrogenase (LDH)

Lactate dehydrogenase (LDH) is primarily used as a biomarker for tissue damage, disease monitoring, and prognostic assessment in various clinical conditions, with particular value in cancer staging, cardiac evaluation, and distinguishing between exudative and transudative pleural effusions. 1

Primary Clinical Applications of LDH

Cancer Diagnosis and Monitoring

• Mandatory tumor marker for advanced germ cell tumors, used alongside AFP and β-HCG 2
• Serves as an important prognostic factor in testicular cancer 2
• Elevated LDH correlates with poor prognosis in solid tumors and hematologic malignancies 1
• Serial measurements help monitor treatment response in cancer patients - normalization suggests treatment response while elevation indicates progression 1
• Not recommended for surveillance in early-stage cancers (stages I-III) due to lack of specificity 1

Pleural Fluid Analysis

• Used to distinguish between exudative and transudative pleural effusions (Light's criteria) 2
• In pleural fluid analysis, LDH >67% of the upper limit of normal serum LDH suggests an exudate 2

Tissue Damage Assessment

• Elevated serum LDH indicates tissue damage as cells release intracellular enzymes through damaged cell membranes 3
• Very high isolated LDH (≥800 IU/ml) warrants thorough investigation for severe underlying disease, particularly:
  • Metastatic cancer (14% vs. 3% in controls)
  • Hematologic malignancies (5% vs. 0% in controls)
  • Infections (57% vs. 28% in controls) 4

Prognostic Value

• Independent predictor of mortality in hospitalized medical patients 4
• Associated with more hospital complications and longer hospital stays 4
• Elevated LDH correlates with reduced response to treatment in cancer patients 1

Laboratory Considerations

Testing Recommendations

• Should be interpreted in context with other clinical and laboratory findings due to low specificity 1
• Serial measurements provide greater value than single determinations 1
• No longer recommended as a standalone test for evaluation of cardiac injury (replaced by troponin) 2

Analytical Issues

• Desirable imprecision (expressed as %CV) of LDH assays has been defined as 10% CV at the 99th percentile reference limit 2
• Clinical laboratories should validate reference intervals based on peer-reviewed literature 2

Specific Disease Applications

Germ Cell Tumors

• Mandatory marker for advanced disease alongside AFP and β-HCG 2
• Important for risk classification in testicular germ cell tumors 2
• Used for diagnosis, prognosis, and monitoring treatment response 2

Cell Death Assessment

• Used in research settings to monitor cell death in laboratory studies 2
• In cytotoxicity assays, LDH release indicates plasma membrane breakdown 2

Other Clinical Applications

• Helpful in differential diagnosis of ascites (malignant vs. non-malignant) 5
• Used in diagnosis of glycogen storage diseases 1
• Elevated in inflammatory diseases and associated with mortality risk in COVID-19 6

Clinical Approach to Elevated LDH

Initial Evaluation

• Complete blood count with differential
• Liver and renal function tests
• Inflammatory markers (CRP, ESR, ferritin)
• D-dimer
• Cardiac markers if cardiac involvement suspected 1

Imaging Studies Based on Clinical Suspicion

• Chest radiograph
• Abdominal ultrasound
• Echocardiography (if cardiac symptoms present)
• CT or MRI based on diagnostic suspicion 1

Cautions and Limitations

• Low specificity as a standalone test - elevated in numerous conditions 1, 7
• Patients should not be treated based solely on elevated LDH 1
• LDH activity can be affected by sample handling, pH, and components in culture medium 2
• LDH patterns vary significantly between species, limiting cross-species application 7