Hemolysis Laboratory Testing
Hemolysis labs consist of three core markers—reticulocyte count, lactate dehydrogenase (LDH), and haptoglobin—which together confirm red blood cell destruction and should be ordered as the essential initial panel. 1
Essential Core Laboratory Tests
The fundamental hemolysis workup requires:
- Reticulocyte count: Elevated levels (typically >3-5%) indicate increased bone marrow production responding to red cell destruction 1
- Lactate dehydrogenase (LDH): A sensitive marker released from lysed red blood cells; elevated levels confirm hemolysis 1, 2
- Haptoglobin: Binds free hemoglobin and becomes depleted during hemolysis; low or undetectable levels support the diagnosis 1, 2
Complete Initial Workup
Beyond the core three markers, the comprehensive initial panel includes:
- Complete blood count (CBC) with differential: Assesses the degree of anemia and identifies white blood cell abnormalities 1
- Fractionated bilirubin: Confirms predominantly unconjugated hyperbilirubinemia, which occurs when hemoglobin breakdown products overwhelm the liver's conjugation capacity 1, 2
Critical Specimen Handling Requirements
Proper collection technique is essential because in vitro hemolysis causes spurious results in over 60% of rejected samples. 1, 3
To prevent false results:
- Use a straight needle rather than butterfly needle during collection 1
- Avoid excessive tourniquet pressure 1
- Process samples within 1 hour at room temperature 1
- Reject visibly hemolyzed samples 1
Second-Line Testing Based on Initial Findings
Once hemolysis is confirmed, additional testing helps identify the underlying cause:
- Direct antiglobulin test (DAT): Differentiates immune-mediated from non-immune hemolysis by detecting antibodies or complement on red blood cell surfaces 1, 4
- G6PD enzyme assay: For suspected enzyme deficiency, particularly in patients of African, Mediterranean, or Asian descent 1
- Hemoglobin electrophoresis: When hemoglobinopathies or thalassemia are suspected 1
- Osmotic fragility or eosin-5-maleimide (EMA) binding test: For suspected membrane defects like hereditary spherocytosis 1
- Blood typing and antibody screen: For immune-mediated hemolysis evaluation 1
Additional Markers of Intravascular Hemolysis
In severe intravascular hemolysis specifically:
- Free hemoglobin: Elevated in plasma when hemolysis overwhelms haptoglobin binding capacity 2, 5
- Hemoglobinuria: Occurs when free hemoglobin exceeds renal threshold 2, 5
- Hemosiderinuria: Indicates chronic intravascular hemolysis 5
These markers are typically reserved for cases with clinical suspicion of severe intravascular hemolysis (incompatible transfusion, G6PD crisis, paroxysmal nocturnal hemoglobinuria) rather than routine screening. 5