Overview of Anaemia

Overview of Anaemia

  • Anaemia is a hematological condition characterized by a reduction in hemoglobin concentration in the blood, affecting the ability to transport oxygen.

Introduction

  • Hemoglobin in red blood cells is crucial for transporting oxygen to tissues and removing carbon dioxide.
  • Anaemia occurs due to reduced red cell mass or decreased hemoglobin concentration, leading to decreased oxygen-carrying capacity of blood.
  • The cardiovascular system undergoes major adaptations in response to anaemia.

Definition of Anaemia

  • Anaemia is defined as a reduction in hemoglobin concentration below the reference range for an individual's age and sex.
  • It results from inherited or acquired causes and is an imbalance between red cell production and loss.

Importance of Diagnosis

  • Anaemia is a common condition globally but is not a standalone diagnosis; rather, it indicates an underlying issue that requires investigation.

WHO Definition of Anaemia

  • For Men: Hemoglobin < 130 g/L
  • For Women: Hemoglobin < 120 g/L
  • Estimated 33% of the global population was affected by anaemia in 2010, with higher prevalence in females and children under 5 years.
  • Significant causes include:
    • Iron deficiency (often from hookworms or schistosomiasis)
    • Sickle cell disease
    • Thalassemia
    • Malaria
    • Anemia from chronic disorders.

Grading of Anaemia

  • Mild: Hemoglobin 10.0 - lower limit of normal
  • Moderate: Hemoglobin 7.0 - 10.0 g/dl
  • Severe: Hemoglobin < 7.0 g/dl

Laboratory Evaluation

Determining Hemoglobin Concentration

  • Colorimetric Methods
    • Visual methods are often inaccurate; the WHO hemoglobin color scale is reliable and cost-effective.
    • Photoelectric Colorimeter Methods:
    • Cyanmethhemoglobin method: Most accurate
    • Oxyhemoglobin method: Reliable but lacks stable standards.
    • Alkaline hematin method: Accurate.

Packed Cell Volume (PCV)

  • PCV measures the volume of packed red cells after centrifugation and is important for diagnosing anaemia.
  • PCV is expressed as a percentage of total blood volume and aids in calculating red cell indices.
  • Two methods for its determination:
    • Macro-method (Wintrobe)
    • Micro-method (Microhaematocrit)

Rule of 3

  • A simplified check:
    • Red cell count (millions/cm³) × 3 = Hemoglobin (g/dl)
    • Hemoglobin (g/dl) × 3 = PCV (%)
  • Primarily applies to normocytic normochromic specimens.

Mechanisms of Anaemia

  1. Impaired Red Cell Production
    • Nutritional deficiencies (Iron, B12, Folate)
    • Aplastic anaemia
    • Diseases affecting the bone marrow
  2. Excessive Red Cell Destruction
    • Hemolytic anaemias
    • Inherited membrane defects (e.g., hereditary spherocytosis)
  3. Dilutional Anaemia: Plasma volume expansion leads to diluted red cell concentration.

Clinical Evaluation of Anaemia

  • A detailed clinical history is essential, focusing on:
    • Blood loss history (acute or chronic)
    • Diet, medical conditions, and medications that may contribute to anaemia
    • Symptoms: Fatigue, dyspnoea on exertion, palpitations, and headache.

Signs of Anaemia

  • General signs: Pallor, tachycardia, and signs of heart failure.
  • Specific signs: Yeast infections or jaundice, specific to types of anaemia like sickle cell.

Investigations for Anaemia

  • A variety of tests including:
    • Full Blood Count (FBC) and Red Cell Indices
    • Peripheral blood smear
    • Reticulocyte count
    • Additional specific investigations depending on the clinical suspicion (e.g. ferritin for iron status).

Red Cell Indices

  • Mean Corpuscular Volume (MCV): Average volume of red cells.
    • High in newborns, slightly increased in pregnancy.
  • Mean Corpuscular Hemoglobin (MCH): Average hemoglobin in red cells; low in microcytic anaemia.
  • Mean Corpuscular Hemoglobin Concentration (MCHC): Average concentration in packed red cells.
  • Red Cell Distribution Width (RDW): Variation in red cell size; useful in assessing certain anaemias.

Classification of Anaemia

  1. Aetiological Classification
  2. Morphological Classification
    • Based on MCV: Microcytic, Normocytic, Macrocytic.

Reticulocyte Count

  • Measures bone marrow activity and response to anemia.
  • Normal count: 0.5-2.5%; indicates production levels.

Examination of Peripheral Blood Smear

  • Morphological assessment critical for diagnosis:
    • Types of cells, signs of hemolysis, size, and shape abnormalities.

Treatment of Anaemia

  • Address underlying causes;
  • Chronic cases often managed on an outpatient basis;
  • Blood transfusions reserved for critical cases.