How is autoimmune hemolytic anemia diagnosed and what are the first‑line treatment options for warm and cold forms?

Diagnosis and Treatment of Autoimmune Hemolytic Anemia

Diagnostic Approach

The diagnosis of AIHA requires a comprehensive laboratory panel including CBC with differential, reticulocyte count, peripheral blood smear, direct antiglobulin test (DAT/Coombs) with monospecific antisera, LDH, haptoglobin, and bilirubin (direct and indirect) before initiating any treatment. 1, 2

Essential Laboratory Findings

• Anemia with macrocytosis on CBC is the initial finding 1, 3
• Elevated reticulocyte count indicates active bone marrow response to hemolysis 1, 3, 4
• Peripheral blood smear showing spherocytes, schistocytes, and other red cell morphology abnormalities 1
• Elevated LDH confirms hemolysis 1, 3
• Decreased or absent haptoglobin is a key marker of intravascular hemolysis 1, 3
• Elevated indirect (unconjugated) bilirubin indicates hemolysis 1, 3
• Positive direct antiglobulin test (DAT/Coombs) with monospecific antisera is mandatory and distinguishes warm (IgG-positive) from cold (C3d/IgM-positive) AIHA 1, 2, 5

Critical Diagnostic Pitfall

A positive DAT alone is insufficient to diagnose AIHA and may be positive in patients without anemia; conversely, some patients with AIHA may have a negative DAT (DAT-negative AIHA), which requires exclusion of other causes of hemolysis and is supported by response to steroids 1, 4

Excluding Secondary Causes

• Obtain detailed medication history evaluating for ribavirin, rifampin, dapsone, interferon, cephalosporins, penicillins, NSAIDs, quinine/quinidine, fludarabine, ciprofloxacin, lorazepam, and diclofenac 1
• Screen for underlying conditions including lymphoproliferative disorders, systemic autoimmune diseases (especially lupus), viral infections (HIV, hepatitis B/C, CMV, parvovirus), and immunodeficiencies 1, 3, 4
• Rule out nutritional deficiencies with B12, folate, copper, and iron studies 1
• Assess G6PD activity to exclude G6PD deficiency 1
• Thyroid function tests should be performed 1

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First-Line Treatment for Warm AIHA

Corticosteroids (prednisone 1-2 mg/kg/day for severe cases or 0.5-1 mg/kg/day for moderate cases) are the definitive first-line treatment for warm AIHA, achieving clinical response in approximately 70-85% of patients. 6, 7, 3, 2

Severity-Based Treatment Algorithm

Grade 1 (Mild): Hemoglobin < lower limit of normal to 10.0 g/dL

• Close clinical monitoring with regular laboratory evaluation 7, 1
• Folic acid 1 mg daily supplementation to support increased erythropoiesis 6, 1
• Corticosteroids may not be immediately necessary 7

Grade 2 (Moderate): Hemoglobin < 10.0 to 8.0 g/dL

• Prednisone 0.5-1 mg/kg/day orally 6, 7, 1
• Monitor hemoglobin weekly until steroid tapering is complete 6
• Assess reticulocyte count, haptoglobin, LDH, and DAT weekly to gauge hemolysis activity 7, 1

Grade 3 (Severe): Hemoglobin < 8.0 g/dL or transfusion indicated

• Prednisone 1-2 mg/kg/day (oral or IV depending on symptom severity) 6, 7, 1
• Consider hospital admission for close monitoring 7, 1
• Mandatory hematology consultation 1
• RBC transfusion using minimum units necessary to relieve symptoms, targeting hemoglobin 7-8 g/dL in stable patients 7, 1

Grade 4 (Life-Threatening): Severe symptomatic anemia

• Immediate hospital admission and urgent hematology consultation 7, 1
• IV methylprednisolone ≥1 mg/kg/day (or 1-2 mg/kg/day) as early as possible 7, 1
• Complete normalization of hemoglobin and laboratory parameters should be the treatment goal 7

Corticosteroid Management Principles

• Prednisone should be rapidly tapered and usually stopped in responders, especially in non-responders after 4 weeks, to avoid corticosteroid-related complications 8
• Pulse dexamethasone (40 mg/day for 4 days) may produce sustained response in 50% of newly diagnosed adults, with some protocols using 4 cycles given every 14 days achieving 86% response rates 8
• High-dose IV methylprednisolone has been used with 80% response rates, though short-term responses may require maintenance oral corticosteroids 8

Adjunctive Therapy

• Intravenous immunoglobulin (IVIG) 0.3-0.5 g/kg may be considered in acute phases or cases with inadequate response to high-dose corticosteroids for rapid but temporary improvement 6, 7, 1
• Avoid IV anti-D in patients with AIHA, as it can exacerbate hemolysis 7
• Avoid fluoroquinolones (such as ciprofloxacin) due to risk of exacerbating hemolysis 6

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Second-Line Treatment for Refractory or Relapsed Warm AIHA

Rituximab (375 mg/m² weekly for 4 weeks) is now the preferred second-line treatment for steroid-refractory or relapsed warm AIHA, with effectiveness in 70-80% of cases. 6, 7, 2, 5

When to Initiate Second-Line Therapy

• If no improvement or worsening on corticosteroids, initiate second-line immunosuppressive therapy 1
• Rituximab should be considered early in severe cases and if no prompt response to steroids is achieved 2

Alternative Second-Line Options

• Immunosuppressive agents such as azathioprine, cyclophosphamide (1-2 mg/kg/day), cyclosporine (3 mg/kg/day, adjusted for target trough levels 100-150 ng/mL), or mycophenolate mofetil may be considered for refractory cases 6, 7, 1, 3

Third-Line Considerations

• Splenectomy yields response in roughly 70% of cases with an estimated cure rate of about 20%; however, rituximab is now preferred because it avoids surgical complications 7
• Before performing splenectomy, a definitive diagnosis must be confirmed and coexisting thrombophilic disorders must be ruled out 1
• Splenectomy typically raises hemoglobin by 1-3 g/dL and can reduce or eliminate transfusion needs 1

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First-Line Treatment for Cold Agglutinin Disease (CAD)

Rituximab with or without bendamustine should be used in the first line for patients with cold agglutinin disease requiring therapy, as patients with cold agglutinins are refractory to steroids and splenectomy. 2, 5

Key Differences from Warm AIHA

• Corticosteroids and splenectomy are ineffective in CAD 3, 2
• DAT is positive with anti-C3d/IgM antisera plus high titer cold agglutinins 9
• Half of CAD patients may respond to rituximab, although responses are usually short-lived 3

Emerging Therapies for CAD

• Complement inhibitors (sutimlimab, riliprubart, pegcetacoplan, iptacopan) have shown utility in stabilizing AIHA patients with acute severe hemolysis 5, 9
• C1s inhibitor sutimlimab is entering phase 3 studies for CAD 5

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Special Clinical Scenarios

Drug-Induced Hemolytic Anemia

If drug-induced hemolytic anemia is suspected, the causative drug must be immediately discontinued, followed by supportive care and corticosteroids (prednisone 0.5-2 mg/kg/day) for moderate to severe cases. 6

Fludarabine-Associated AIHA

Fludarabine-containing regimens should be avoided in patients with a history of AIHA because fludarabine can trigger or exacerbate AIHA; if AIHA develops during fludarabine therapy, the drug must be stopped immediately and never re-introduced. 7

AIHA in Chronic Lymphocytic Leukemia (CLL)

• For patients with stable CLL and uncomplicated autoimmune hemolysis, corticosteroids remain the recommended first-line therapy 7
• In CLL-associated warm AIHA, rituximab should be considered before splenectomy 7
• Autoimmune cytopenias that fail to respond to standard AIHA treatments constitute an indication to initiate CLL-directed therapy 7
• Patients whose cytopenias are immune-mediated experience better clinical outcomes than those with bone-marrow infiltration 7

Thrombotic Microangiopathy (TTP/HUS)

When the triad of non-immune hemolytic anemia, thrombocytopenia, and renal involvement is present, immediate hematology consultation and plasma exchange according to existing guidelines are required to distinguish TTP/HUS from AIHA. 8, 1

• ADAMTS13 activity should be determined urgently (severely deficient, measuring <10 IU/dL in TTP) 8
• Test for verocytotoxin-producing E. coli (VTEC) in stool 8

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Monitoring and Supportive Care

• Monitor hemoglobin levels weekly while on corticosteroids 6, 7
• Assess reticulocyte count, bilirubin, LDH, and haptoglobin regularly to evaluate response 7, 1
• Folic acid 1 mg daily should be administered to support increased erythropoiesis 6, 1
• Transfuse red blood cells only to the minimum needed to relieve symptoms; irradiate all blood products to prevent transfusion-associated graft-versus-host disease in appropriate settings 7
• Close contact with the transfusion service is necessary if transfusion is required 4