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).