When should lactate dehydrogenase (LDH) testing be performed?

When to Test Lactate Dehydrogenase (LDH)

LDH testing should be performed in advanced malignancies, suspected tissue damage, hemolysis, and specific organ disorders, but is not recommended for routine screening or surveillance in early-stage disease due to its lack of specificity. 1

Primary Indications for LDH Testing

Oncology Indications

• Advanced malignancies:
  • Advanced germ cell tumors (mandatory for staging and prognosis) 2
  • Metastatic solid tumors (for prognostic assessment) 1
  • Hematologic malignancies (lymphomas, multiple myeloma) 1
  • Melanoma (stage IV only, not recommended for stages I-III) 1

Non-oncologic Indications

• Suspected tissue damage:

  • Myocardial infarction (especially LDH-1 isoenzyme) 3
  • Pulmonary disorders (pleural effusions, lung damage) 2, 4
  • Liver disease (particularly LDH-5 isoenzyme) 1
  • Skeletal muscle injury 1

• Fluid analysis:

  • Pleural effusions (to distinguish exudates from transudates) 2
  • Peritoneal fluid (secondary peritonitis evaluation) 1

• Hemolysis evaluation:

  • Suspected hemolytic anemia 1
  • Intravascular hemolysis 1

When NOT to Test LDH

• Early-stage malignancies (stages I-III) 1
• Routine health screening (lacks specificity) 1
• Follow-up of treated localized renal masses (only at clinician's discretion) 2

Clinical Context for LDH Testing

Oncology Context

• Initial diagnosis and staging:

  • Mandatory in advanced germ cell tumors along with AFP and β-HCG 2
  • Important prognostic factor prior to treatment 2

• Treatment monitoring:

  • Serial measurements help monitor disease progression and treatment efficacy 1
  • Consider monitoring during treatment of stage IV disease 1

Diagnostic Workup Context

• Pleural effusions:

  • Include LDH in basic pleural fluid analysis 2
  • Helps distinguish exudative from transudative effusions 2

• Renal masses follow-up:

  • May be used at clinician's discretion but not routinely recommended 2
  • Consider if clinical symptoms suggest disease progression 2

Interpretation Considerations

• Normal range: 125-220 U/L (or IU/L) in adults 1

• Markedly elevated levels (>900 IU/L) suggest:

  • Hematologic malignancies 1, 5
  • Metastatic disease 5
  • Severe infections 5

• Isolated very high LDH (≥800 IU/L without liver enzyme elevation):

  • Strong marker for cancer (27% of cases) 5
  • Associated with higher mortality (26.6% vs 4.3% in controls) 5
  • Independent predictor of mortality in hospitalized patients 5

Common Pitfalls and Caveats

• Lack of specificity: LDH elevation occurs in numerous conditions, limiting its diagnostic value when used alone 1, 6
• Treatment decisions: Patients should not be treated based solely on elevated LDH 1
• Isoenzyme patterns: Total LDH has less clinical significance than isoenzyme fractions in many conditions 6
• Species differences: LDH patterns vary significantly between species (important in veterinary medicine) 6

Recommended Complementary Tests

• For elevated LDH:

  • Complete blood count with differential
  • Liver and renal function tests
  • C-reactive protein and ESR
  • Specific markers based on clinical suspicion (troponin for cardiac, D-dimer for thrombosis) 1

• Imaging studies based on clinical findings:

  • Chest radiograph
  • Abdominal ultrasound
  • CT or MRI based on diagnostic suspicion 1

Remember that LDH elevation is a nonspecific finding that requires clinical correlation and often additional testing to determine its significance.