What is the initial workup and treatment for a patient presenting with anemia?

Initial Workup and Treatment for Anemia

The initial workup for anemia should include a complete blood count with red cell indices, reticulocyte count, peripheral blood smear, serum ferritin, transferrin saturation, and CRP, followed by targeted treatment based on the identified cause. 1

Diagnostic Approach

Step 1: Initial Laboratory Assessment

• Complete blood count (CBC) with:
  • Hemoglobin level
  • Red cell indices (MCV, MCH, RDW)
  • White blood cell count and differential
  • Platelet count
• Reticulocyte count
• Peripheral blood smear examination
• Serum ferritin level
• Transferrin saturation (TSAT)
• C-reactive protein (CRP) or other inflammatory markers 1

Step 2: Classification Based on MCV

1. Microcytic anemia (MCV < 80 fL):

   • Iron studies (serum iron, TIBC, ferritin)
   • Consider hemoglobin electrophoresis if thalassemia suspected
   • RDW can help distinguish iron deficiency from thalassemia 2, 3

2. Normocytic anemia (MCV 80-100 fL):

   • If reticulocyte count is high: evaluate for hemolysis or blood loss
     • LDH, haptoglobin, bilirubin, direct antiglobulin test
   • If reticulocyte count is low/normal: consider anemia of chronic disease, renal disease, or early deficiency 2

3. Macrocytic anemia (MCV > 100 fL):

   • Vitamin B12 and folate levels
   • Liver function tests
   • Thyroid function tests
   • Review medication history (azathioprine, methotrexate)
   • Consider alcohol use assessment 4

Step 3: Additional Testing Based on Initial Results

• If iron deficiency suspected: serum ferritin < 30 ng/mL is diagnostic
• If ferritin 30-100 ng/mL with elevated CRP: consider combined iron deficiency and anemia of chronic disease 1
• If B12 deficiency suspected: methylmalonic acid and homocysteine levels may be helpful
• If hemolysis suspected: LDH, haptoglobin, reticulocyte count, bilirubin 1

Treatment Algorithm

Iron Deficiency Anemia

1. Oral iron therapy:

   • First-line treatment: 100-200 mg elemental iron daily
   • Monitor response with hemoglobin check at 4 weeks
   • Continue for 3-6 months after normalization to replenish stores 1, 3

2. IV iron:

   • Consider if oral iron not tolerated or ineffective
   • Indicated in patients with inflammatory bowel disease with active inflammation
   • More rapid correction of anemia than oral iron 1, 5

Vitamin B12 Deficiency

1. Parenteral B12 therapy:

   • Initial: 100 mcg daily intramuscularly for 6-7 days
   • Followed by 100 mcg every 3-4 days until normalization
   • Maintenance: 100 mcg monthly for life in pernicious anemia 6

2. Oral B12 supplementation:

   • Option for patients with normal intestinal absorption
   • Not reliable for pernicious anemia 6

Folate Deficiency

• Oral folate supplementation: 1-5 mg daily for 3-6 months 4

Anemia of Chronic Disease

• Treat underlying condition
• Consider erythropoiesis-stimulating agents if appropriate
• IV iron may be beneficial even with normal or elevated ferritin 5

Special Considerations

When to Consider Bone Marrow Examination

• Unexplained cytopenias
• Suspected myelodysplastic syndrome
• No response to appropriate therapy
• Abnormal cells on peripheral smear 4

When to Consider GI Evaluation

• Iron deficiency anemia in men or postmenopausal women
• No obvious source of blood loss
• Persistent anemia despite appropriate therapy 3

Follow-up Monitoring

• Repeat CBC in 4-8 weeks to assess response to treatment
• Expect hemoglobin increase of at least 2 g/dL with appropriate therapy
• For unexplained anemia, close follow-up with CBC every 6 months 4

Common Pitfalls to Avoid

• Treating anemia without identifying the underlying cause
• Missing concurrent iron deficiency in macrocytic anemia
• Relying solely on MCV to rule out vitamin deficiencies
• Overlooking medication effects on blood counts
• Failing to investigate alcohol use in macrocytic anemia 4
• Neglecting to consider anemia of chronic disease when ferritin is normal or elevated 1

By following this systematic approach to the workup and treatment of anemia, clinicians can efficiently identify the underlying cause and implement appropriate therapy to improve patient outcomes.