Reticulocyte Count

Aka: Reticulocyte Count, Retic Count, Absolute Reticulocyte Count, Reticulocyte Index, Reticulocytopenia, Reticulocytosis

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II. Indication

  1. Anemia Evaluation

III. Contraindications

  1. Recent Transfusion (not diagnostic after transfusion)

IV. Measures

  1. Reticulocyte Count
    1. Reticulocyte percentage of total erythrocytes
    2. Does not correct for degree of Anemia
  2. Absolute Reticulocyte Count (ARC)
    1. Number of Reticulocytes present in 1 mm3 blood
    2. ARC = (Reticulocyte %) / 100 * Erythrocyte Count
  3. Reticulocyte Index (RI)
    1. Adjusts Reticulocyte Count for Hematocrit
    2. Reticulocyte Index reflects Bone Marrow activity
      1. Known as "Poor man's Bone Marrow Aspirate"
    3. Calculation
      1. RI = Reticulocyte Count x (HCT / normal HCT)

V. Technique

  1. Stain Solution (Stains ribosomes)
    1. New methylene blue or Azure B 1.0 grams
    2. Dissolve stain in 100 ml Citrate-Saline
      1. Tri-Sodium citrate 3% (one part)
      2. Saline 0.85% (four parts)
    3. Filter solution
    4. Store at 4 degrees celsius
  2. Staining method
    1. Start with 2-3 drops of stain in tube
    2. Add 2-3 drops of patient's blood
      1. Use more blood in anemic patients
      2. Use less blood in polycythemia
    3. Incubate at 37 degrees celsius for 15-20 minutes
    4. Gently mix
    5. Create a thin film on slide
    6. Allow films to dry
  3. Counting method
    1. View field of undistorted cells at x100 oil immersion
      1. Reticulocytes stain deep blue
      2. Red Blood Cells stain pale-greenish blue
    2. Use Miller ocular insert
      1. nRBC: average Red Blood Cells in small square
      2. nRetic: Number of Reticulocytes in 'nField' fields
    3. Calculate Reticulocyte Count
      1. Calculate Reticulocytes per 1000 red cells
      2. Retic Count = (nRetic) / (9 * nRBC * nField)

VI. Interpretation

  1. Normal Reticulocyte Count: 0.5-1.5%
  2. Normal Reticulocyte Index: 1-3%

VII. Reticulocytosis (Increased RBC Production)

  1. Criteria
    1. Reticulocyte Index >3%
    2. Reticulocyte Count >1.5%
  2. Conditions
    1. Acute blood loss or Hemorrhage
    2. Post-Splenectomy
    3. Acute Hemolytic Anemia (Microangiopathic Anemia)
      1. Example: Autoimmune Hemolytic Anemia
      2. Usually ARC > 100 x10^6/L and Retic Count >2%
    4. Hemoglobinopathy
      1. Sickle Cell Anemia
      2. Thalassemia major
    5. Post-Anemia Treatment
      1. Folate Supplementation
      2. Iron Supplementation
      3. Vitamin B12 Supplementation

VIII. Reticulocytopenia (Decreased RBC Production)

  1. Criteria
    1. Reticulocyte Index <1%
    2. Reticulocyte Count <0.5%
  2. Conditions
    1. Aplastic Anemia
    2. Bone Marrow infiltrate
    3. Bone Marrow suppression or failure
      1. Sepsis
      2. Chemotherapy or Radiotherapy
    4. Disordered RBC maturation
      1. Iron Deficiency Anemia
      2. Vitamin B12 Deficiency
      3. Folate Deficiency
      4. Sideroblastic Anemia
      5. Anemia of Chronic Disease
      6. Hypothyroidism
    5. Blood Transfusion
    6. Liver disease

IX. Resources

  1. HTP Blood Safety and Clinical Technology
    1. http://w3.whosea.org/haem/c12.htm

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