What labs are used to diagnose and manage anemia?

Laboratory Tests for Diagnosing and Managing Anemia

The essential laboratory tests for diagnosing and managing anemia include complete blood count (CBC), reticulocyte count, iron studies (serum ferritin and transferrin saturation), and other specialized tests based on the suspected cause. 1

Core Laboratory Tests

Initial Evaluation

• Complete Blood Count (CBC)

  • Hemoglobin (preferred over hematocrit for diagnosis) 2
  • Mean Corpuscular Volume (MCV) - classifies anemia as microcytic, normocytic, or macrocytic
  • Red Blood Cell Distribution Width (RDW)
  • White blood cell count and platelet count (to assess other cell lines) 2

• Reticulocyte Count

  • Essential for evaluating bone marrow erythropoietic activity 1
  • Helps classify anemia as due to decreased production or increased destruction/loss 2
  • Can be expressed as absolute count or reticulocyte index (adjusted for degree of anemia) 2

Iron Status Assessment

• Serum Ferritin

  • Surrogate marker for tissue iron stores 2
  • Values <30 μg/L typically indicate iron deficiency 1
  • May be elevated in inflammation regardless of iron stores 2

• Transferrin Saturation (TSAT)

  • Represents iron available for erythropoiesis 2
  • More reliable marker than ferritin in chronic kidney disease patients as it's less affected by inflammation 2

Classification-Based Testing

Based on MCV Classification

Parameter	Iron Deficiency	Thalassemia Trait	Anemia of Chronic Disease
MCV	Low	Very low (<70 fl)	Low/Normal
RDW	High (>14%)	Normal (≤14%)	Normal/Slightly elevated
Ferritin	Low (<30 μg/L)	Normal	Normal/High
TSAT	Low	Normal	Low
RBC count	Normal/Low	Normal/High	Normal/Low

Additional Tests Based on Initial Findings

• For Microcytic Anemia

  • Hemoglobin electrophoresis (if thalassemia suspected)
  • Lead levels (if lead toxicity suspected)

• For Macrocytic Anemia

  • Vitamin B12 and folate levels
  • Thyroid function tests
  • Liver function tests

• For Hemolytic Anemia

  • Lactate dehydrogenase (LDH)
  • Haptoglobin
  • Direct Coombs test
  • Peripheral blood smear

Special Considerations

Advanced Iron Assessment

• Percent Hypochromic Red Blood Cells (PHRBC) and Content of Hemoglobin in Red Blood Cells (CHr)
  • May have greater sensitivity and specificity than ferritin and transferrin saturation 2
  • Limited by need for specialized equipment and time-sensitivity of samples 2

Inflammatory Markers

• C-reactive protein
  • Useful to assess contribution of inflammation to elevated ferritin levels 2
  • Helps interpret iron studies in chronic disease

Timing of Measurements

• For hemodialysis patients, predialysis hemoglobin measurements are recommended 2
• Hemoglobin should be measured at least annually in all chronic kidney disease patients 1
• More frequent monitoring (every 3-6 months) for patients with greater disease burden or unstable clinical course 1

Common Pitfalls to Avoid

• Relying solely on hemoglobin/hematocrit without further investigation of the cause 2
• Failing to consider that no single test is definitive for diagnosing iron deficiency 2
• Not accounting for the effect of inflammation on ferritin levels 2
• Overlooking the need to screen for gastrointestinal bleeding in non-menstruating patients with iron deficiency 2
• Inadequate follow-up monitoring after initiating treatment 1

By following this comprehensive laboratory approach to anemia diagnosis and management, clinicians can effectively identify the underlying cause and monitor treatment response, ultimately improving patient outcomes.