What labs should be checked for anemia in a patient with a history of burns?

Laboratory Evaluation for Anemia in Burn Patients

A comprehensive anemia workup in patients with a history of burns should include a complete blood count (CBC), reticulocyte count, serum ferritin, transferrin saturation (TSAT), and C-reactive protein (CRP) as the core laboratory tests. 1

Primary Laboratory Tests

• Complete Blood Count (CBC):

  • Hemoglobin (preferred over hematocrit for diagnosing anemia) 2
  • White blood cell count
  • Platelet count
  • Mean corpuscular volume (MCV) - low MCV suggests iron, folate, or B12 deficiency 2

• Iron Studies:

  • Serum ferritin (to assess iron stores)
    • <30 μg/L indicates absent/low iron stores in non-inflammatory states 1
    • Note: May be elevated in burn patients due to inflammatory response regardless of actual iron stores 2
  • Transferrin saturation (TSAT) (to assess available iron for erythropoiesis)
    • <20% suggests iron deficiency 1
    • More reliable than ferritin in burn patients due to less influence from inflammation 2

• Reticulocyte Count:

  • Evaluates bone marrow response to anemia 2
  • Low count in burn patients may indicate inadequate erythropoietin production or functional iron deficiency 2

Additional Recommended Tests

• C-reactive protein (CRP):

  • Helps assess contribution of inflammation to elevated ferritin levels 2, 1
  • Particularly important in burn patients who often have significant inflammatory response 3

• Vitamin B12 and Folate levels:

  • To rule out deficiencies that may contribute to anemia 1

• Liver Function Tests:

  • Part of initial workup for anemia 1

Special Considerations for Burn Patients

Burn patients present unique challenges when evaluating anemia due to:

1. Multiple etiologies of anemia:

   • Persistent blood loss from burn wounds and surgical procedures 3, 4
   • Decreased erythropoiesis 3
   • Inflammation-induced functional iron deficiency 2

2. Interpretation challenges:

   • Ferritin acts as an acute phase reactant and may be falsely elevated 2
   • TSAT is more reliable in the setting of inflammation 2

3. Monitoring frequency:

   • Regular monitoring is essential as burn patients often remain anemic throughout hospitalization 3
   • Consider more frequent monitoring (every 1-2 weeks) during acute phase 1

Clinical Pearls and Pitfalls

• Pitfall: Relying solely on ferritin to assess iron status in burn patients can lead to missed iron deficiency due to inflammation-induced elevation.

• Pearl: Consider percent hypochromic red blood cells (PHRBC) or content of hemoglobin in red blood cells (CHr) if available, as these may be more sensitive markers of functional iron deficiency 2

• Pitfall: Failing to distinguish between anemia due to acute surgical blood loss versus anemia of critical illness. Approximately 52% of transfusions in burn patients are related to anemia of critical illness rather than surgical blood loss 4

• Pearl: The severity of critical illness (measured by APACHE II score) and duration of critical illness (ventilator days) correlate with transfusion requirements related to anemia of critical illness 4

By following this comprehensive laboratory evaluation approach, clinicians can better identify the specific causes of anemia in burn patients and guide appropriate treatment strategies.