What is the appropriate diagnostic workup and treatment for a patient suspected of having hemolytic anemia?

Hemolytic Workup

Initial Laboratory Panel

Begin with a complete blood count with red blood cell indices, peripheral blood smear, reticulocyte count, lactate dehydrogenase, haptoglobin, indirect bilirubin, and direct antiglobulin test with monospecific antisera to establish the diagnosis and differentiate immune from non-immune causes. 1, 2

Essential First-Line Tests

• Complete blood count with red blood cell indices assesses anemia severity and red cell characteristics 1
• Peripheral blood smear identifies schistocytes (suggesting thrombotic microangiopathy), spherocytes (autoimmune hemolytic anemia or hereditary spherocytosis), or other morphologic abnormalities 1, 2
• Reticulocyte count evaluates bone marrow compensatory response, which should be elevated in hemolysis unless marrow involvement, nutritional deficiency, or autoimmune suppression is present 1, 2
• Lactate dehydrogenase (LDH) serves as a marker of intravascular hemolysis, though note that 25% of autoimmune hemolytic anemia cases may present with normal LDH levels 1, 3
• Haptoglobin decreases in hemolysis due to binding free hemoglobin 1, 2
• Indirect bilirubin elevates from red cell breakdown 1, 2
• Direct antiglobulin test (DAT/Coombs test) with monospecific antisera differentiates autoimmune hemolytic anemia from other causes and guides subsequent workup 1, 2

Critical History and Physical Examination Elements

Drug Exposure History

• Specifically inquire about ribavirin, rifampin, dapsone, interferon, cephalosporins, penicillins, NSAIDs, quinine/quinidine, fludarabine, and ciprofloxacin 1

Infection History

• Recent mycoplasma or viral infections can trigger hemolysis 1
• Insect, spider, or snake bites may cause hemolysis 1

Family and Neonatal History

• Family history of anemia, jaundice, splenomegaly, or early cholecystectomy suggests hereditary hemolytic conditions 1
• Neonatal jaundice history suggests congenital hemolytic disorders 1

Physical Findings

• Assess for jaundice, splenomegaly, pallor, and dark urine 1

Algorithmic Approach Based on Direct Antiglobulin Test Results

If DAT is Positive (IgG and/or C3d)

This indicates immune-mediated hemolysis requiring further characterization. 4

• DAT positive with IgG only or IgG + C3d: Warm autoimmune hemolytic anemia is the primary consideration 4, 5

  • Obtain autoimmune serology (ANA, etc.) to evaluate for underlying systemic autoimmune disease 1, 2
  • Perform protein electrophoresis and cryoglobulin analysis to exclude lymphoproliferative disorders 1
  • Review medication history for drug-induced hemolysis 4, 6

• DAT positive with C3d only: Consider cold agglutinin disease, paroxysmal cold hemoglobinuria, or drug-induced hemolysis 5

  • Obtain cold agglutinin titer and thermal amplitude studies 5
  • Perform Donath-Landsteiner test if paroxysmal cold hemoglobinuria is suspected 5

If DAT is Negative

This suggests non-immune hemolysis or DAT-negative autoimmune hemolytic anemia. 4, 6

• Glucose-6-phosphate dehydrogenase (G6PD) assay evaluates enzyme deficiency 1
• Paroxysmal nocturnal hemoglobinuria screening by flow cytometry is necessary 1
• Hemoglobin electrophoresis evaluates hemoglobinopathies 1
• Osmotic fragility test or eosin-5-maleimide binding test if hereditary spherocytosis is suspected based on smear morphology 7
• Pyruvate kinase activity assay for suspected enzyme deficiencies 2

If Microangiopathic Features Present (Schistocytes on Smear)

Urgent evaluation for thrombotic microangiopathy is required, as schistocyte counts >1% support the diagnosis, though their absence does not exclude early disease. 4

• ADAMTS13 activity level must be obtained urgently; levels <10% indicate thrombotic thrombocytopenic purpura requiring immediate plasma exchange 4
• DIC panel including PT/INR, fibrinogen, and D-dimer 1
• Complete blood count with platelet count to assess for thrombocytopenia, which combined with hemolysis suggests thrombotic microangiopathy 4
• Creatinine to evaluate for renal involvement 4

Do not delay plasma exchange while awaiting ADAMTS13 results if thrombotic thrombocytopenic purpura is strongly suspected clinically. 4

Second-Tier Testing for Refractory or Unclear Etiology

• Bone marrow analysis with cytogenetic studies evaluates myelodysplastic syndromes or marrow failure 1
• Vitamin B12, folate, and copper levels exclude nutritional causes of inadequate reticulocyte response 1
• Parvovirus B19 testing if reticulocytopenia is present 1
• Iron studies and thyroid function as part of comprehensive evaluation 1
• Methemoglobin level if cyanosis or oxidative drug exposure is present 1
• Genetic testing (e.g., PKLR gene for pyruvate kinase deficiency) for suspected congenital disorders 2

Treatment Approach Based on Severity and Etiology

For Autoimmune Hemolytic Anemia

Treatment severity is graded based on hemoglobin level and clinical symptoms. 2

Mild (Grade 1)

• Close clinical follow-up with regular laboratory monitoring 2
• Folic acid 1 mg daily supplementation to support increased erythropoiesis 2

Moderate (Grade 2)

• Prednisone 0.5-1 mg/kg/day 2, 8
• Folic acid supplementation 2

Severe (Grade 3)

• Prednisone 1-2 mg/kg/day (oral or IV depending on symptom severity) 2, 8
• Consider hospital admission based on clinical judgment 2
• Obtain hematology consultation 2, 4
• RBC transfusion as needed, targeting hemoglobin of 7-8 g/dL in stable patients 2, 4
• Consider adding rituximab early in severe cases or if no prompt response to steroids 9

Life-threatening (Grade 4)

• Admit patient to hospital for close monitoring 2
• Urgent hematology consultation 2, 4
• IV methylprednisolone 1-2 mg/kg/day 2
• Consider second-line immunosuppressive therapy if no improvement or worsening while on corticosteroids: rituximab, intravenous immunoglobulin (IVIG), cyclosporine A, or mycophenolate mofetil 2
• RBC transfusion according to existing guidelines 2

For Cold Agglutinin Disease

• Rituximab with or without bendamustine should be used in the first line for patients requiring therapy 9
• Keep patient warm as foundational management 5
• Consider monoclonal antibodies against C1q or C5 for significant complement-related outcomes 5

For Drug-Induced Hemolytic Anemia

• Immediately discontinue the suspected causative drug 2
• Treat with corticosteroids as per severity grading above 2

For Thrombotic Thrombocytopenic Purpura

• Do not delay plasma exchange while awaiting ADAMTS13 results 4
• Administer methylprednisolone 1g IV daily for 3 days starting after first plasma exchange 4

For Atypical Hemolytic Uremic Syndrome

• Begin eculizumab therapy urgently 4
• Administer meningococcal vaccination and long-term penicillin prophylaxis 4

Critical Pitfalls to Avoid

• Do not exclude thrombotic microangiopathy based on "rare" schistocytes alone, as their absence does not exclude early disease 4
• Do not assume elevated LDH is required for hemolysis diagnosis, as 25% of autoimmune hemolytic anemia cases may have normal LDH 3
• Do not transfuse more than the minimum necessary units, and discuss with blood bank if thrombotic microangiopathy is suspected before transfusing 4
• Do not dismiss DAT-negative results as excluding autoimmune hemolytic anemia; this can occur with low antibody levels or IgA/IgM antibodies not detected by standard testing 6, 5

When to Obtain Urgent Hematology Consultation

• Any grade 3 or higher hemolytic anemia 2, 4
• Suspected thrombotic microangiopathy with thrombocytopenia 4
• Unclear etiology after initial workup 4
• Refractory cases not responding to first-line therapy 2