Approach to Assessment of Anemia

Definition and Classification

• Anemia is defined as hemoglobin concentration below 130 g/L in men over 15 years and below 120 g/L in non-pregnant women over 15 years 1, 2
• The World Health Organization defines anemia as a hemoglobin level below 130 g/L for men and below 120 g/L for women 1, 2

Severity Classification

• Mild anemia is classified as Hb ≤11.9 g/dL and ≥10 g/dL 3, 4
• Moderate anemia is classified as Hb ≤9.9 g/dL and ≥8.0 g/dL 3, 4
• Severe anemia is classified as Hb <8.0 g/dL 3, 4

Differential Diagnosis

• Iron deficiency anemia is the most common cause of anemia, often due to GI blood loss, menstrual bleeding, or malabsorption 1, 6
• Anemia of chronic disease is associated with inflammatory conditions, malignancy, or chronic infections 3, 4, 5
• Chronic kidney disease can cause anemia due to erythropoietin deficiency 2
• Vitamin B12 or folate deficiency can cause macrocytic anemia, often due to pernicious anemia, malabsorption, or dietary insufficiency 4, 5

Investigation

• A complete blood count (CBC) with differential is essential for diagnosing anemia, including hemoglobin, MCV, MCH, RDW, white blood cells, and platelets 2, 5, 6
• Reticulocyte count helps assess bone marrow response 4, 2, 5
• Serum ferritin is the most specific test for iron deficiency, with levels <15 μg/L diagnostic and <30 μg/L suggesting low stores 1, 6
• Transferrin saturation and C-reactive protein help diagnose iron deficiency and inflammation 4, 1, 5

Treatment

• The American Gastroenterological Association recommends identifying and treating the underlying cause of iron deficiency anemia, especially GI sources of blood loss 1, 6
• Oral iron supplementation is the first-line treatment for mild to moderate iron deficiency anemia, with parenteral iron reserved for severe cases or intolerance 1, 6
• The National Kidney Foundation recommends correcting nutritional deficiencies, such as iron, B12, and folate, before using erythropoiesis-stimulating agents in patients with chronic kidney disease 2

Referral

• Urgent hematology referral is recommended for abnormalities in two or more cell lines, severe anemia without obvious cause, suspected hemolysis, or unexplained anemia after extended workup 2, 3, 4, 5
• Fast-track GI referral is recommended for iron deficiency anemia with Hb <110 g/L in men or <100 g/L in non-menstruating women, suspected colorectal cancer, or any iron deficiency anemia in adults without significant non-GI blood loss 1, 6