Is Serum LDH of 202 U/L Elevated or a Sign of Ischemia?
A serum lactate dehydrogenase (LDH) level of 202 U/L is not elevated and does not indicate ischemia. This value falls well within the normal reference range and has no clinical significance for tissue ischemia.
Normal Reference Range Context
- Normal serum LDH levels typically range from 313-618 U/L, meaning your value of 202 U/L is actually below the lower limit of normal 1
- The British Thoracic Society guidelines reference LDH in the context of pleural fluid analysis, where pleural fluid LDH is compared to serum LDH, with normal serum values serving as the denominator in diagnostic ratios 2
LDH Elevation Thresholds for Clinical Significance
- Mild elevation is considered 2-3 times the upper limit of normal (approximately 620-1,860 U/L) 1
- Very high isolated LDH is defined as ≥800 U/L, which is associated with serious underlying disease including metastatic cancer, hematologic malignancies, and infection 3
- Extremely high LDH (>10 times normal, or >6,180 U/L) carries a mortality rate exceeding 50% and requires intensive care in 73% of cases 1
LDH as a Marker of Ischemia
- For mesenteric ischemia specifically, serum lactate (not LDH) is the relevant biomarker, with lactate >2 mmol/L indicating potential irreversible intestinal ischemia (Hazard Ratio: 4.1) 2, 4
- Serum LDH is an unspecific marker of tissue hypoperfusion and only undergoes significant elevation after advanced tissue damage has occurred 5
- In thrombotic thrombocytopenic purpura (a condition causing systemic ischemia), elevated LDH results from release from multiple damaged tissues rather than being a direct marker of ischemia itself 6
Important Clinical Distinction
- Do not confuse serum lactate with serum LDH—these are entirely different laboratory tests 2, 4
- Serum lactate (measured in mmol/L) is the appropriate marker for acute tissue ischemia and hypoperfusion 2, 4
- Serum LDH (measured in U/L) is a non-specific marker that elevates in numerous conditions including hemolysis, liver disease, malignancy, and advanced tissue necrosis 3, 1
Clinical Bottom Line
Your LDH value of 202 U/L requires no further investigation and provides no evidence of ischemia or any pathological process. If ischemia is suspected clinically, measure serum lactate instead, with levels >2 mmol/L warranting concern, particularly when accompanied by symptoms such as abdominal pain 2, 4.