Decreasing LDH Without Treatment Is Not Indicative of Myelodysplastic Syndrome (MDS)
A decreasing lactate dehydrogenase (LDH) level without treatment is not indicative of myelodysplastic syndrome (MDS) and may actually suggest an alternative diagnosis, as MDS is typically associated with normal or elevated LDH levels that have prognostic significance.
Role of LDH in MDS Diagnosis and Monitoring
LDH is considered an important laboratory parameter in the evaluation of MDS, but its diagnostic and prognostic significance differs from what the question suggests:
Diagnostic Value: According to ESMO clinical practice guidelines 1, LDH is one of several laboratory values that support or exclude the diagnosis of MDS, alongside ferritin, transferrin, reticulocyte counts, vitamin B12, folate, haptoglobin, and erythropoietin levels.
Prognostic Value: Elevated LDH in MDS is associated with:
Pattern of LDH Changes in MDS
The pattern of LDH changes in MDS typically follows these characteristics:
- Initial Presentation: LDH is often normal or elevated at diagnosis 1
- Disease Progression: LDH tends to increase, not decrease, as disease progresses 3
- Monitoring Value: Serial determinations showing increasing LDH levels can predict disease progression 3-6 months before other clinical signs appear 3
Clinical Implications of Decreasing LDH
A decreasing LDH without treatment in a patient with suspected MDS:
May suggest alternative diagnoses such as:
- Resolution of a temporary condition causing LDH elevation (infection, hemolysis)
- Vitamin B12 or folate deficiency that is spontaneously improving
- Transient bone marrow suppression from medications or toxins
Is inconsistent with typical MDS progression, where LDH tends to remain stable or increase over time 3
Diagnostic Approach for Suspected MDS
For accurate MDS diagnosis, the following are essential:
- Peripheral blood counts and differential showing cytopenias (typically anemia) 1
- Bone marrow examination showing dysplastic features in ≥10% of cells in one or more cell lineages 1
- Cytogenetics to identify characteristic chromosomal abnormalities 1
- Exclusion of other causes of cytopenias and dysplasia 1
Monitoring Recommendations
If MDS is still suspected despite decreasing LDH:
- Monitor complete blood counts for persistent or worsening cytopenias
- Consider bone marrow examination if cytopenias persist
- Track LDH trends over time - in true MDS, LDH typically stabilizes or increases 3
- Evaluate for other causes of decreasing LDH (resolution of hemolysis, infection, etc.)
Conclusion
A decreasing LDH without treatment should prompt reconsideration of an MDS diagnosis rather than supporting it. In established MDS, LDH is an important monitoring parameter where increases (not decreases) correlate with disease progression and poorer outcomes.