What is the initial workup for a patient with hemolytic anemia?

Hemolytic Anemia Workup

The initial workup for hemolytic anemia should include a complete blood count with red cell indices, reticulocyte count, peripheral blood smear, markers of hemolysis (LDH, haptoglobin, indirect bilirubin), and direct antiglobulin test (DAT/Coombs), followed by targeted testing based on the suspected etiology. 1

First-Line Laboratory Tests

Essential Initial Studies

• Complete blood count (CBC) with red cell indices to confirm anemia and determine if normocytic, microcytic, or macrocytic 1
• Reticulocyte count which is typically elevated in hemolytic anemia, indicating increased red cell production in response to hemolysis 2, 1
• Peripheral blood smear to evaluate red cell morphology (schistocytes, spherocytes, agglutination) which provides critical clues to etiology 2, 1, 3
• Direct antiglobulin test (DAT/Coombs test) to distinguish immune from non-immune causes 2, 1, 3

Hemolysis Markers

• Lactate dehydrogenase (LDH) - elevated in hemolysis 2, 1, 3
• Haptoglobin - decreased or absent in hemolysis 2, 1, 3
• Indirect (unconjugated) bilirubin - elevated in hemolysis 2, 1, 3
• Free hemoglobin - elevated particularly in intravascular hemolysis 2

History and Physical Examination Specifics

Critical Historical Elements

• Recent medication exposure including ribavirin, rifampin, dapsone, interferon, cephalosporins, penicillins, NSAIDs, quinine/quinidine, fludarabine, ciprofloxacin, lorazepam, diclofenac 2
• Insect, spider, or snake bites which can trigger hemolysis 2
• Family history to identify potential hereditary causes 1
• Recent blood transfusions which can affect test results, particularly DAT and enzyme assays 1

Physical Examination Findings

• Look for jaundice, pallor, splenomegaly, dark-colored urine, and signs of underlying systemic disease 2, 3

Second-Line Testing Based on Initial Results

If DAT Positive (Immune-Mediated)

• Autoimmune serology including ANA, anti-dsDNA, complement levels (C3, C4) 2
• Protein electrophoresis and cryoglobulin analysis to evaluate for lymphoproliferative disorders 2
• Cold agglutinin titers if cold agglutinin disease suspected 2

If DAT Negative (Non-Immune)

• Glucose-6-phosphate dehydrogenase (G6PD) assay for suspected enzymopathy 2, 1
• Paroxysmal nocturnal hemoglobinuria (PNH) screening by flow cytometry 2, 1
• Red cell enzyme assays particularly for pyruvate kinase deficiency in transfusion-dependent patients with undiagnosed anemia 1
• Molecular/genetic testing for hereditary hemolytic anemias when suspected 1

Additional Specialized Testing

• Disseminated intravascular coagulation (DIC) panel including PT/INR to evaluate for consumptive coagulopathy 2
• Evaluation for viral/bacterial causes including mycoplasma, parvovirus B19, and other infectious triggers 2
• Assessment of methemoglobinemia if clinically indicated 2
• Osmotic fragility testing or eosin-5-maleimide (EMA) binding test for hereditary spherocytosis 3

When to Perform Bone Marrow Examination

• Suspicion of infiltrative disease or myelodysplastic syndromes when no obvious cause identified 2, 1
• Refractory cases requiring cytogenetic analysis 2
• Suspected red cell aplasia when reticulocyte count is inappropriately low despite anemia 2, 4
• Evaluation for bone marrow failure syndrome if refractory, including assessment for B12, folate, copper, iron deficiencies, thyroid dysfunction, and infection 2

Common Pitfalls and Caveats

DAT-Negative AIHA

• Up to 10% of autoimmune hemolytic anemia cases may be DAT-negative 5
• Diagnosis requires exclusion of other causes of hemolysis and is supported by response to steroids 5
• These cases are often more severe and may require multiple treatments 5

Inadequate Reticulocyte Response

• Up to 30% of AIHA patients show inappropriately low reticulocyte counts despite hemolysis 4
• This indicates inadequate bone marrow compensation and is associated with more severe anemia and transfusion needs 4
• Consider measuring endogenous erythropoietin levels in these cases 4

Timing Considerations

• Recent transfusion can interfere with DAT results and red cell enzyme assays - ideally obtain pre-transfusion samples when possible 1
• Neonatal presentation with rapid onset anemia or significant hyperbilirubinemia should prompt urgent consideration of hemolytic anemia 3

Secondary Causes Requiring Investigation

• Perform ultrasound/CT imaging and consider bone marrow evaluation to exclude hematologic malignancies in appropriate clinical contexts 5
• Check immunoglobulin levels if frequent infections or suspected immunodeficiency 5
• Screen for systemic autoimmune diseases with autoantibody panel if signs/symptoms present 5