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Peripheral Blood Smear (PBS) Interpretation Guide

Comparison Table for Peripheral Blood Smear Findings in Various Diseases

Disease

RBC Findings

WBC Findings

Platelet Findings

ABO Incompatibility

Spherocytes (3+), Polychromasia (2+), Nucleated RBCs (1+)

Neutrophilia (2+), Left Shift

Normal Count and Morphology

Iron Deficiency Anemia

Microcytes (2+), Hypochromia (2+), Target Cells (1+)

Generally normal

Often elevated (reactive thrombocytosis)

Thalassemia

Microcytes (3+), Hypochromia (3+), Basophilic Stippling (2+), Target Cells (3+)

Generally normal

Generally normal

Sickle Cell Disease

Sickle Cells (3+), Target Cells (2+), Polychromasia (2+)

Leukocytosis during vaso-occlusive crises

Generally normal

Hereditary Spherocytosis

Spherocytes (3+), Polychromasia (2+)

Generally normal

Generally normal

Immune Thrombocytopenic Purpura (ITP)

Generally normal

Generally normal

Thrombocytopenia, Large platelets

Thrombotic Thrombocytopenic Purpura (TTP)

Schistocytes (2+)

Generally normal

Thrombocytopenia

Hemolytic Uremic Syndrome (HUS)

Schistocytes (2+)

Generally normal

Thrombocytopenia

Disseminated Intravascular Coagulation (DIC)

Schistocytes (3+)

Variable, often leukocytosis

Thrombocytopenia

Explanation of Findings

RBC Findings

  • Spherocytes: Small, dense RBCs without central pallor; seen in hereditary spherocytosis and ABO incompatibility.

  • Polychromasia: Bluish-tinted cells indicating increased reticulocytes; seen in conditions with increased RBC production.

  • Nucleated RBCs: Immature red blood cells; seen in severe hemolytic anemias and bone marrow stress.

  • Microcytes: Small RBCs; seen in iron deficiency anemia and thalassemia.

  • Hypochromia: Pale RBCs due to low hemoglobin; seen in iron deficiency anemia and thalassemia.

  • Target Cells: Bullseye appearance; seen in liver disease, thalassemia, and hemoglobinopathies.

  • Basophilic Stippling: Fine granules in RBCs; seen in lead poisoning, thalassemia, and sideroblastic anemia.

  • Sickle Cells: Crescent-shaped RBCs; seen in sickle cell disease.

  • Schistocytes: Fragmented RBCs indicating mechanical damage; seen in DIC, TTP, and other hemolytic processes.

WBC Findings

  • Neutrophilia: Increased neutrophils; seen in infections and inflammatory conditions.

  • Left Shift: Presence of band cells indicating an active marrow response; seen in bacterial infections.

  • Leukocytosis: Increased white blood cell count; seen in infections and inflammatory conditions.

  • Generally Normal: No significant abnormalities.

Platelet Findings

  • Thrombocytopenia: Low platelet count; seen in ITP, TTP, HUS, and DIC.

  • Reactive Thrombocytosis: Elevated platelet count; seen in iron deficiency anemia.

  • Large Platelets: Indicates increased production; seen in ITP.

  • Generally Normal: No significant abnormalities.

This table summarizes the typical findings for each condition, providing a quick reference for interpreting peripheral blood smears in various pediatric hematologic disorders.


Image credit: Pediatric on Squares https://x.com/OnSquares/status/1470751344378228746
 

Grading System for Qualitative Analysis

  • Percentage of cells affected in high-power field:

    • 1+: 25%

    • 2+: 25-50%

    • 3+: 50-75%

    • 4+: 75-100%

This grading system is used to quantify the extent of various abnormalities seen in RBCs, WBCs, and platelets.

Red Blood Cells (RBCs)

Using the provided image, here's a detailed examination of RBC morphology:

Size Variation (Anisocytosis)

  • Normal: Standard size RBCs without significant variation.

  • Microcyte: Smaller than normal RBCs.

  • Macrocyte: Larger than normal RBCs.

Hemoglobin Distribution

  • Hypochromia: RBCs with reduced hemoglobin content.

  • Polychromasia: RBCs with a bluish tint, indicating immature red cells (reticulocytes).

Shape Variation (Poikilocytosis)

  • Target Cell: RBCs with a bullseye appearance, often seen in liver disease, thalassemia, and hemoglobinopathies.

    • Why: These cells indicate abnormal hemoglobin content or structural integrity.

    • Additional Conditions: Iron deficiency anemia, post-splenectomy states.

  • Acanthocyte: Spur cells with irregular projections, seen in liver disease, abetalipoproteinemia, and lipid disorders.

    • Why: Due to altered lipid composition in the RBC membrane.

    • Additional Conditions: McLeod syndrome.

  • Spherocyte: Small, dense, and round RBCs without central pallor, typical of hemolytic anemias like hereditary spherocytosis and ABO incompatibility.

    • Why: Due to membrane protein defects or immune-mediated damage.

    • Additional Conditions: Autoimmune hemolytic anemia.

  • Helmet Cell: Fragmented RBCs, often seen in microangiopathic hemolytic anemias (MAHAs) such as DIC, TTP, and HUS.

    • Why: Mechanical damage as RBCs pass through microvascular abnormalities.

    • Additional Conditions: Severe burns.

  • Ovalocyte (aka Elliptocyte): Oval-shaped RBCs, seen in hereditary elliptocytosis and various anemias.

    • Why: Due to membrane protein defects.

    • Additional Conditions: Iron deficiency anemia, myelodysplastic syndromes.

  • Schistocyte: Fragmented RBCs indicating mechanical damage, seen in DIC, TTP, and other hemolytic processes.

    • Why: Shearing forces in the vasculature.

    • Additional Conditions: Mechanical heart valves.

  • Stomatocyte: RBCs with a mouth-shaped area of central pallor, seen in hereditary stomatocytosis and liver disease.

    • Why: Altered ion content within RBCs affecting membrane shape.

    • Additional Conditions: Alcoholic liver disease.

  • Tear Drop: RBCs shaped like teardrops, seen in myelofibrosis and other marrow infiltration disorders.

    • Why: Mechanical distortion during RBC development.

    • Additional Conditions: Thalassemias.

  • Sickle Cell: Crescent-shaped RBCs, seen in sickle cell disease.

    • Why: Abnormal hemoglobin (HbS) polymerization under low oxygen conditions.

    • Additional Conditions: None.

  • Burr Cell: RBCs with short, evenly spaced projections, seen in uremia, liver disease, and pyruvate kinase deficiency.

    • Why: Altered cell membrane due to metabolic or environmental factors.

    • Additional Conditions: Gastric cancer.

Inclusions

  • Pappenheimer Bodies: Iron-containing granules in RBCs, seen in sideroblastic anemia and post-splenectomy.

    • Why: Abnormal iron metabolism within RBCs.

    • Additional Conditions: Myelodysplastic syndromes.

  • Cabot's Ring: Ring-shaped structures in RBCs, seen in severe anemia and lead poisoning.

    • Why: Remnants of mitotic spindle.

    • Additional Conditions: Pernicious anemia.

  • Basophilic Stippling: Coarse granules in RBCs, seen in lead poisoning, thalassemia, and sideroblastic anemia.

    • Why: Aggregated ribosomal RNA.

    • Additional Conditions: Alcohol abuse.

  • Howell-Jolly Bodies: Nuclear remnants in RBCs, seen in asplenia or after splenectomy.

    • Why: Failure to remove nuclear remnants.

    • Additional Conditions: Severe anemia.

Red Cell Distribution

  • Agglutination: Clumping of RBCs, often due to cold agglutinins or autoimmune hemolytic anemia.

    • Why: IgM antibody-mediated RBC clumping.

    • Additional Conditions: Mycoplasma pneumonia, infectious mononucleosis.

  • Rouleaux: Stacking of RBCs like coins, seen in high protein states like multiple myeloma and chronic inflammatory states.

    • Why: Increased plasma proteins (IgG) decreasing zeta potential.

    • Additional Conditions: Waldenström's macroglobulinemia, Multiple myeloma

White Blood Cells (WBCs)

  • Count and Distribution: Estimate the relative proportions of different WBC types.

    • Neutrophils: Usually the most abundant, look for segmentation (bands and segmented).

    • Lymphocytes: Smaller with a large nucleus.

    • Monocytes: Larger cells with a folded or indented nucleus.

    • Eosinophils: Bilobed nucleus with red-orange granules.

    • Basophils: Bilobed or S-shaped nucleus with dark blue granules.

  • Morphology: Check for any abnormal features.

    • Toxic Granulation: Coarse granules in neutrophils, indicating severe infection or inflammation.

    • Atypical Lymphocytes: Larger with abundant cytoplasm, seen in viral infections like infectious mononucleosis.

    • Blast Cells: Large immature cells, indicating leukemia.

    • Band Cells: Immature neutrophils, indicative of a left shift often seen in bacterial infections.

Platelets

  • Count: Estimate the number of platelets. Generally, 1 dot in high power field (HPF) x 15,000 is roughly equivalent to the platelet count (e.g., 10 dots in HPF approximately equals 150,000 platelets).

    • Thrombocytopenia: Low platelet count.

    • Thrombocytosis: High platelet count.

  • Morphology: Examine the size and appearance.

    • Normal: Small, disc-shaped.

    • Giant Platelets: Seen in some myeloproliferative disorders.

    • Clumping: Platelet clumps can falsely lower automated counts.

Example Interpretations in Pediatric Ward

ABO Incompatibility

  • RBC Findings:

    • Spherocytes 3+: Small, dense RBCs without central pallor.

    • Polychromasia 2+: Bluish-tinted cells, indicating increased reticulocytes.

    • Nucleated RBCs (NRBCs) 1+: Presence of immature red blood cells.

  • WBC Findings:

    • Neutrophilia 2+: Increased neutrophils, possibly with toxic granulation.

    • Left Shift: Presence of band cells, indicating an active marrow response.

  • Platelet Findings:

    • Normal Count and Morphology: Platelets typically appear normal.

Iron Deficiency Anemia

  • RBC Findings:

    • Microcytes 2+: Small RBCs.

    • Hypochromia 2+: Pale RBCs due to low hemoglobin.

    • Target Cells 1+: Occasionally seen.

  • WBC Findings:

    • Generally normal unless there's concurrent infection.

  • Platelet Findings:

    • Often elevated (reactive thrombocytosis).

Thalassemia

  • RBC Findings:

    • Microcytes 3+: Small RBCs.

    • Hypochromia 3+: Pale RBCs.

    • Basophilic Stippling 2+: Fine granules in RBCs.

    • Target Cells 3+: Commonly seen.

  • WBC Findings:

    • Generally normal unless there's concurrent infection.

  • Platelet Findings:

    • Generally normal.

Sickle Cell Disease

  • RBC Findings:

    • Sickle Cells 3+: Crescent-shaped RBCs.

    • Target Cells 2+: Bullseye appearance.

    • Polychromasia 2+: Increased reticulocytes.

  • WBC Findings:

    • Leukocytosis during vaso-occlusive crises.

  • Platelet Findings:

    • Generally normal.

Hereditary Spherocytosis

  • RBC Findings:

    • Spherocytes 3+: Small, dense RBCs without central pallor.

    • Polychromasia 2+: Bluish-tinted cells.

  • WBC Findings:

    • Generally normal unless there's concurrent infection.

  • Platelet Findings:

    • Generally normal.

Immune Thrombocytopenic Purpura (ITP)

  • RBC Findings:

    • Generally normal.

  • WBC Findings:

    • Generally normal.

  • Platelet Findings:

    • Thrombocytopenia: Low platelet count.

    • Large platelets: Indicates increased production.

Thrombotic Thrombocytopenic Purpura (TTP)

  • RBC Findings:

    • Schistocytes 2+: Fragmented RBCs.

  • WBC Findings:

    • Generally normal.

  • Platelet Findings:

    • Thrombocytopenia: Low platelet count.

Hemolytic Uremic Syndrome (HUS)

  • RBC Findings:

    • Schistocytes 2+: Fragmented RBCs.

  • WBC Findings:

    • Generally normal.

  • Platelet Findings:

    • Thrombocytopenia: Low platelet count.

Disseminated Intravascular Coagulation (DIC)

  • RBC Findings:

    • Schistocytes 3+: Fragmented RBCs.

  • WBC Findings:

    • Variable, often leukocytosis.

  • Platelet Findings:

    • Thrombocytopenia: Low platelet count.

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