From the Guidelines
Elevated lactate dehydrogenase (LDH) and decreased haptoglobin levels are indicative of hemolysis, particularly in conditions such as pyruvate kinase deficiency, as seen in studies like 1 and 1. When evaluating for hemolysis, LDH and haptoglobin are typically ordered together, along with other markers like bilirubin and reticulocyte count.
- Normal LDH values range from approximately 140-280 U/L, though reference ranges vary by laboratory.
- Normal haptoglobin ranges from 30-200 mg/dL. In hemolytic conditions, you'll typically see:
- Elevated LDH, as cells are damaged and release this enzyme into the bloodstream.
- Decreased or undetectable haptoglobin, as it is consumed during hemolytic processes. This pattern is particularly useful in distinguishing intravascular hemolysis from extravascular hemolysis, with more dramatic changes seen in intravascular hemolysis. These markers help diagnose conditions like:
- Autoimmune hemolytic anemia
- Sickle cell disease
- Thalassemias
- Mechanical hemolysis from prosthetic heart valves It's worth noting that while LDH and haptoglobin are important markers, other evidence such as 1 and 1 may not be directly relevant to the evaluation of LDH and haptoglobin in the context of hemolysis, and thus should not influence the interpretation of these markers in this specific context. However, the most recent and highest quality study, 1, provides strong evidence for the role of LDH and haptoglobin in evaluating hemolysis, particularly in pyruvate kinase deficiency. Therefore, in the context of evaluating hemolysis, particularly in conditions like pyruvate kinase deficiency, elevated LDH and decreased haptoglobin levels are key diagnostic markers, as supported by studies like 1 and 1.
From the Research
LDH and Haptoglobin Relationship
- LDH (lactate dehydrogenase) and haptoglobin are two biomarkers used to evaluate hemolysis in patients 2, 3.
- Haptoglobin binds to free hemoglobin in the blood, preventing its toxic effects, while LDH is an enzyme released from damaged red blood cells 4, 5.
- In cases of hemolysis, haptoglobin levels decrease as it binds to free hemoglobin, and LDH levels increase as red blood cells are broken down 2, 3.
Clinical Usefulness of LDH and Haptoglobin
- Serum haptoglobin measurement can be used as a laboratory marker for the diagnosis of hemolytic anemia, especially in recently transfused patients 6.
- LDH is a convenient biomarker of intravascular hemolysis and NO bioavailability, characterizing a clinical subphenotype of hemolysis-associated vasculopathy in patients with sickle cell disease 2.
- Haptoglobin testing can be used to evaluate hemolysis, but its interpretation can be difficult in certain settings, such as inflammation, and requires understanding of its principles and limitations 4.
Hemolytic Anemia Diagnosis
- Hemolytic anemia is defined by the premature destruction of red blood cells and can be chronic or life-threatening 3.
- Laboratory test results that confirm hemolysis include reticulocytosis, increased LDH, increased unconjugated bilirubin, and decreased haptoglobin levels 3.
- A peripheral blood smear should be performed when hemolysis is present to identify abnormal red blood cell morphologies, and the direct antiglobulin test can further differentiate immune causes from nonimmune causes 3.