Anemia: Comprehensive Overview

Definition of Anemia

  • Anemia: Inability of circulating blood to supply adequate oxygen to tissues for proper metabolic function.
  • Diagnosis: Made based on:
    • Patient History
    • Physical Examination
    • Signs and Symptoms
    • Hematology Lab Findings
  • Classification: Decrease in hemoglobin (Hgb), red blood cell (RBC) count or hematocrit value.

Causes of Anemia

  • Underlying Diseases: Conditions like renal disease and hemorrhoids can lead to anemia.
  • Common Indicators:
    • Decreased Hemoglobin (Hgb)
    • Decreased Hematocrit (Hct)
    • Decreased RBC Count

Severity of Anemia

  • Most patients exhibit low hemoglobin levels:
    • Moderate Anemia: Hgb 70-100 g/L
    • Severe Anemia: Hgb < 70 g/L
  • Symptoms may include:
    • Dyspnea (SOB)
    • Lightheadedness
    • Vertigo
    • Muscle Weakness
    • Headaches
    • Lethargy
  • Transfusion Guidelines: Recommended when Hgb is < 60 g/L; careful of antibody introduction with transfusions.

Hemoglobin Reference Ranges

  • Infants:
    • Newborn > 1 week: 140-220 g/L
    • 6 months old: 110-140 g/L
  • Children (1-15 years): 110-150 g/L
  • Adults:
    • Men: 140-180 g/L
    • Women: 120-160 g/L

Factors Influencing Hemoglobin Levels

  • Geography: Elevations above 8000 ft can elevate Hgb.
  • Diseases: Lung diseases and nutritional deficiencies (e.g. Iron, B12).
  • Blood Loss: Significant factor leading to anemia.
  • Destruction: Hemolytic anemias, ineffective production due to bone marrow issues.

Classification of Anemia

  • Categories:
    • Hypoproliferative: Low reticulocyte count.
    • Hemolytic: Increased destruction of RBCs.
    • Combination: Both hypoproliferative and hemolytic.
  • Clinically classified by cause:
    • Blood loss, iron deficiency, nutritional deficiency, infection.
  • Quantitative Parameters:
    • Normochromic, hypochromic, hyperchromic (based on cell color).
    • Normocytic, microcytic, macrocytic (based on cell size).

Hemoglobin & Hematocrit Measurements

  • Hgb and Hct are primary metrics to determine anemia.
  • Reference Ranges:
    • Men: 0.420-0.520 L/L
    • Women: 0.370-0.470 L/L
  • Appropriate blood smear is critical for lab evaluation.

RBC Indices

  • Mean Corpuscular Volume (MCV): Measures the size of red blood cells.
    • Normalizing criteria:
    • Normocytic if MCV is in reference range.
    • Microcytic if less than normal.
    • Macrocytic if greater.
  • Mean Corpuscular Hemoglobin (MCH):
    • Captures hemoglobin content per RBC.
  • Mean Corpuscular Hemoglobin Concentration (MCHC):
    • Normal: Normochromic.
    • Decreased: Hypochromic.

Red Blood Cell Indices Diagnostic Utility

  • MCV: Most stable parameter for monitoring.
  • A shift in MCV might indicate clinical events:
    • Cold agglutinin, transfusion therapy, reticulocytosis.
  • Some conditions may create variability prompting further investigation.

Reticulocyte Count

  • Indicates bone marrow response.
  • Calculated as a percentage, absolute count; normal range 0.5-2.0%.
  • Manual Counts: Lack reproducibility.

Bone Marrow Assessment for Anemia

  • Evaluates maturation of red and white cells.
  • Presence and ratio of megakaryocytes important for diagnosis.

Peripheral Blood Smear Analysis

  • Can indicate macrocytic anemia through observations of neutrophils.
  • Structures like Howell-Jolly bodies and Cabot rings provide diagnostic clues to underlying conditions including aplastic anemia or lead poisoning.

Critical Values and Errors in Testing

  • Critical Values: Immediate action required if out of reference range (e.g., Hgb < 70 g/L).
  • Errors can stem from:
    • Sample handling and drawing errors for hemoglobin and hematocrit assessments.
  • Rule of 3: Ensures quality assurance for CBC (RBC x 3 = Hgb; Hgb x 3 = Hct).