Why Lactate Dehydrogenase (LDH) is Trended in Clinical Practice
Lactate dehydrogenase (LDH) is primarily trended to monitor disease progression, treatment response, and prognosis in various conditions, particularly in malignancies, infections, and tissue damage, as it serves as a marker of cell turnover and tissue destruction.
Key Clinical Applications for LDH Monitoring
1. Oncology Applications
Malignancies with established utility:
- Testicular cancer: LDH is a mandatory marker for advanced disease staging and prognostication 1
- Melanoma: LDH is incorporated into AJCC staging for stage IV disease, where elevated levels are associated with worse survival and may predict treatment response 1
- Hematologic malignancies: Elevated LDH indicates higher tumor burden and cell turnover 1
Monitoring treatment response:
- In germ cell tumors, LDH normalization suggests effective treatment, while rising levels may indicate treatment failure 1
- For melanoma patients with stage IV disease, LDH is measured to assess disease progression 1
- However, LDH should not be used alone to guide treatment decisions for seminoma patients 1
2. Infectious and Inflammatory Conditions
- Sepsis monitoring: LDH elevation can reflect tissue hypoxia and cell damage in septic patients 1
- COVID-19 severity: High LDH levels predict mortality and disease severity in COVID-19 patients 2
- General infections: LDH is significantly elevated (57% vs 28%) in patients with infections compared to controls 3
3. Prognostic Value
- Mortality prediction: Very high isolated LDH (≥800 IU/ml) is an independent predictor of mortality in hospitalized patients 3
- Hospital complications: Elevated LDH correlates with longer hospital stays (9.3 vs 4.1 days) and higher in-hospital complication rates 3
- Disease severity: LDH levels >10 times normal are associated with poor prognosis regardless of etiology (mortality >50%) 4
Limitations and Considerations
- Low specificity: LDH elevation occurs in numerous conditions (43 different etiologies reported) 4
- False positives: High false-positive rate limits utility in some contexts 1
- Confounding factors: Various treatments like blood transfusions, growth factors, radiotherapy, and chemotherapy can influence LDH levels 4
Disease-Specific Recommendations
For Melanoma
- LDH should be measured in patients with stage IV melanoma 1
- Not recommended for routine surveillance in early-stage (stage 0-II) melanoma 1
- Rising levels may indicate disease progression in advanced disease 1
For Testicular Cancer/Germ Cell Tumors
- Mandatory marker along with AFP and β-HCG for staging and monitoring 1
- Not recommended for guiding treatment decisions in pure seminoma 1
- Not recommended for routine monitoring of treatment response in seminoma, but should be measured when treatment concludes 1
For General Medical Patients
- Consider trending LDH when monitoring patients with:
- Known malignancy, especially with metastatic disease
- Severe infections or sepsis
- Conditions with significant tissue damage or high cell turnover
Biochemical Basis for LDH Monitoring
LDH is an enzyme involved in anaerobic glycolysis, converting pyruvate to lactate. Its release into circulation occurs when cell membranes are damaged, making it a marker of cell death and tissue destruction 5. The enzyme exists in five isoforms with different tissue distributions, allowing for some degree of organ specificity when fractionated 5.
In summary, while LDH lacks specificity as a standalone diagnostic test, its value lies in monitoring disease progression, treatment response, and prognosis when used in appropriate clinical contexts and in conjunction with other clinical and laboratory parameters.