Summary of "CCH Session 1 - ABC of CBC 21st May 2023 IAP Delhi Certificate Course in Hematology"

Summary of “CCH Session 1 - ABC of CBC 21st May 2023 IAP Delhi Certificate Course in Hematology”

This session, led by Dr. Manas Kalra, consultant hematologist at Sir Ganga Ram Hospital, provides a comprehensive overview of the Complete Blood Count (CBC) and its interpretation, focusing on pediatric hematology. The lecture emphasizes the importance of understanding CBC parameters beyond the common ones (hemoglobin, MCV, TLC, platelet count) to diagnose a wide spectrum of hematological and non-hematological conditions effectively.

Main Ideas and Concepts

1. Introduction to CBC and Its Importance

CBC is a fundamental yet often underutilized diagnostic tool.
Pediatricians must understand age-related changes in CBC parameters.
CBC interpretation aids in diagnosing anemia types, infections, hemoglobinopathies, bone marrow disorders, and more.

2. Age-Related Variations in CBC

Hemoglobin, reticulocyte count, MCV, and lymphocyte counts vary significantly with age.
Newborns have high hemoglobin and reticulocytes; physiological anemia occurs around 2–3 months.
Pediatricians must interpret CBC values in the context of age-specific reference ranges.

3. Classification and Interpretation of Anemia Using CBC Parameters

Key parameters: Hemoglobin, MCV (Mean Corpuscular Volume), RDW (Red Cell Distribution Width), RBC count.
Anemia classification by MCV:
- Microcytic (low MCV)
- Normocytic (normal MCV)
- Macrocytic (high MCV)
RDW helps differentiate types of microcytic anemia:
- High RDW: nutritional anemia (iron, B12, folate deficiency), thalassemia major.
- Normal RDW: thalassemia minor.
RBC count distinguishes iron deficiency (low RBC) from thalassemia minor (high RBC).
Rule of Three: RBC count × 3 ≈ Hemoglobin; Hemoglobin × 3 ≈ Hematocrit. Deviations indicate pathology.

4. Common Anemia Cases and Lessons

Case of severe anemia in a 3-year-old with microcytic anemia and high RDW likely iron deficiency or mixed with thalassemia minor.
Importance of correcting iron deficiency before performing HPLC for thalassemia diagnosis.
Differentiation of thalassemia major, intermedia, and minor based on CBC, peripheral smear, and clinical features.
Role of peripheral smear in identifying nucleated RBCs, target cells, and other morphological clues.

5. Advanced and Newer CBC Parameters

Reticulocyte Hemoglobin Content (CHr) and Reticulocyte Hemoglobin Equivalent (Ret-He) indicate functional iron availability over recent days.
Percentage hypochromic cells and low hemoglobin density are useful in complex cases (e.g., chronic kidney disease, chronic inflammation).
Immature Reticulocyte Fraction (IRF) indicates bone marrow recovery.
Nucleated RBC counts and corrected WBC counts in cases with nucleated RBCs.

6. Interpretation of Special CBC Patterns

Macrocytic anemia can be:
- Megaloblastic (B12/folate deficiency)
- Non-megaloblastic (aplastic anemia, inherited bone marrow failure syndromes like Fanconi anemia, Diamond-Blackfan anemia)
Pancytopenia requires bone marrow evaluation for leukemia, aplastic anemia, HLH, or marrow infiltration.
High MCHC and anemia with splenomegaly suggest hereditary spherocytosis; diagnosis aided by EMA binding test and osmotic fragility.
CBC abnormalities due to technical issues (e.g., lipemic serum causing falsely high hemoglobin and MCHC; RBC agglutination causing abnormal counts).

7. White Blood Cell (WBC) and Platelet Interpretation

Importance of Differential Leukocyte Count (DLC) in evaluating neutropenia, lymphocytosis, blasts, and leukemoid reactions.
Neutropenia requires urgent evaluation; congenital neutropenia can respond to G-CSF.
Lymphocytosis may indicate infections like infectious mononucleosis or pertussis.
Platelet count and size (MPV) help differentiate immune thrombocytopenia (ITP) from inherited platelet disorders like Bernard-Soulier syndrome.
Immature Platelet Fraction (IPF) is useful in monitoring platelet production and recovery.
Thrombocytosis can be reactive (e.g., infection, iron deficiency).

8. Practical Tips and Clinical Pearls

Always consider age-appropriate reference ranges.
Use bedside formulas for MCV interpretation (e.g., lower limit = 70 + age; upper limit = 84 + 0.6 × age).
Check for rule of three discrepancies to suspect mixed or unusual anemia.
Peripheral smear examination is crucial alongside CBC.
Correct iron deficiency before diagnosing thalassemia minor.
In post-transfusion patients, wait for transfused RBCs to clear before re-evaluation.
Be cautious interpreting CBC in presence of technical artifacts (lipemia, agglutination).
Neutropenia and abnormal DLC require urgent attention and further workup.
Always correlate CBC findings with clinical context and other investigations.

Detailed Methodologies and Instructions

Bedside MCV Interpretation

Lower limit of MCV = 70 + age (years)
Upper limit of MCV = 84 + (0.6 × age)
MCV < lower limit = microcytosis; MCV > upper limit = macrocytosis

Rule of Three

RBC count × 3 ≈ Hemoglobin
Hemoglobin × 3 ≈ Hematocrit (PCV)
Deviations suggest mixed or abnormal conditions.

Corrected WBC Count in Presence of Nucleated RBCs

Corrected WBC = (Reported WBC × 100) / (100 + number of nucleated RBCs per 100 WBCs)

Corrected Reticulocyte Count

Corrected Retic % = Retic % × (Patient’s Hematocrit / Normal Hematocrit) Helps assess bone marrow response relative to anemia severity.

Use of Menzer Index to Differentiate Iron Deficiency and Thalassemia Minor

Menzer Index = MCV / RBC count
< 13 suggests thalassemia minor
13 suggests iron deficiency anemia
Use only in mild anemia, not severe anemia.

Peripheral Smear Examination

Look for nucleated RBCs, target cells, spherocytes, basophilic stippling, tear-drop cells.
Helps differentiate hemolytic anemias, thalassemias, and other disorders.

Diagnosis of Hereditary Spherocytosis

High MCHC (>35), presence of spherocytes on smear.
Confirm with EMA binding test and osmotic fragility.

Reticulocyte Hemoglobin Content (CHr)

Value < 28 pg indicates functional iron deficiency.
Value < 25 pg indicates iron deficiency anemia.

Handling Lipemic Samples

Remove plasma, dilute with saline, then re-run CBC to avoid false high hemoglobin/MCHC.

Key Takeaways

CBC is a powerful diagnostic tool when interpreted with clinical context and peripheral smear.
Understanding RBC indices (MCV, RDW, RBC count) and their interplay is essential to classify anemia.
New parameters like reticulocyte hemoglobin content enhance diagnostic accuracy in complex cases.
WBC and platelet counts, along with differential counts and morphology, provide clues to infections, leukemia, immune disorders, and inherited conditions.
Technical artifacts can mislead CBC interpretation; awareness and correction are necessary.
Always consider age-specific reference ranges and clinical presentation.
Post-transfusion CBC interpretation requires caution.
Peripheral smear remains an indispensable adjunct to CBC.

Speakers and Sources

Dr. Manas Kalra – Consultant Hematologist, Sir Ganga Ram Hospital, Delhi; main presenter.
Dr. Ajay, Dr. Vipul, Dr. Kamaljit, Dr. Lynn, Dr. Gigi, Dr. Benita, Dr. Manish – Faculty and panelists participating in Q&A.
Organizers of IAP Delhi Certificate Course in Hematology – Course hosts.

This session provides a detailed, practical guide to CBC interpretation in pediatric hematology, blending fundamental principles with advanced concepts and real-life case discussions. It is valuable for pediatricians, hematologists, and trainees aiming to enhance diagnostic skills using CBC data.