Lesson 2 of 635 min read

Hematology

Complete Blood Count, Anemias, Leukemias, and Hemostasis

In This Lesson

1. Complete Blood Count 2. RBC Indices & Morphology 3. Anemias Classification 4. WBC Differential 5. Leukemias & Lymphomas 6. Platelets & Disorders 7. Coagulation Cascade 8. Hemostasis Disorders

1. Complete Blood Count

Normal Values

Parameter	Male	Female	Units
RBC	4.5-5.5	4.0-5.0	×10¹²/L
Hemoglobin	14-18	12-16	g/dL
Hematocrit	42-52	37-47	%
WBC	4.5-11.0		×10⁹/L
Platelets	150-400		×10⁹/L

Specimen Collection

Anticoagulant: EDTA (purple/lavender top) - chelates calcium
Ratio: 1.5-2.0 mg/mL of blood
Storage: Room temp up to 24 hours; refrigerated up to 48 hours
Mixing: Gentle inversion 8-10 times to prevent clotting

2. RBC Indices & Morphology

Red Cell Indices

MCV (Mean Cell Volume)

= Hct × 10 / RBC

Normal: 80-100 fL

Size of RBCs

MCH (Mean Cell Hgb)

= Hgb × 10 / RBC

Normal: 27-31 pg

Hgb per cell

MCHC (Mean Cell Hgb Conc)

= Hgb × 100 / Hct

Normal: 32-36 g/dL

Hgb concentration

RBC Morphology Terms

Size Variations

Anisocytosis: Variation in size (↑RDW)
Microcytes: Small (<7μm)
Macrocytes: Large (>8.5μm)

Shape Variations

Poikilocytosis: Variation in shape
Target cells: Liver disease, thalassemia
Sickle cells: Sickle cell disease

Color Variations

Hypochromia: Pale center >1/3
Polychromasia: Bluish tint (young RBCs)

Inclusions

Howell-Jolly: Nuclear remnants (asplenia)
Basophilic stippling: RNA (lead poisoning)
Heinz bodies: Denatured Hgb (G6PD)

3. Anemias Classification

By MCV Classification

Microcytic (MCV <80)

• Iron deficiency
• Thalassemia
• Sideroblastic
• Lead poisoning
• Chronic disease (some)

Normocytic (MCV 80-100)

• Acute blood loss
• Hemolytic anemia
• Aplastic anemia
• Chronic disease
• Renal failure

Macrocytic (MCV >100)

• B12 deficiency
• Folate deficiency
• Liver disease
• Alcoholism
• Myelodysplasia

Iron Studies

Condition	Serum Iron	TIBC	Ferritin	% Sat
Iron Deficiency	↓	↑	↓	↓
Chronic Disease	↓	↓	↑/N	N/↓
Sideroblastic	↑	N/↓	↑	↑

Hemolytic Anemias

Intrinsic (RBC defects)

Membrane: Spherocytosis, Elliptocytosis
Enzyme: G6PD, Pyruvate kinase
Hemoglobin: Sickle cell, Thalassemia

Extrinsic (External)

Immune: AIHA, HDN, Transfusion
Mechanical: TTP, HUS, DIC
Infections: Malaria, Clostridium

Lab Findings in Hemolysis:

↑ Indirect bilirubin, ↑ LDH, ↑ Reticulocytes, ↓ Haptoglobin
Direct Coombs positive in immune hemolysis

4. WBC Differential

Normal WBC Differential

Cell Type	%	Absolute	Function
Neutrophils	40-70%	2.0-7.5 ×10⁹/L	Bacterial infection
Lymphocytes	20-40%	1.0-4.0	Viral, immune
Monocytes	2-8%	0.2-0.8	Chronic infection
Eosinophils	1-4%	0.1-0.4	Parasites, allergy
Basophils	0-1%	0-0.1	Allergy (histamine)

Shift to Left & Right

Left Shift (↑ immature)

• Increased bands (>10%)
• Metamyelocytes, myelocytes
• Indicates acute bacterial infection
• Bone marrow releasing immature cells

Right Shift (↑ hypersegmented)

• >5 lobes in neutrophils
• B12 or folate deficiency
• Megaloblastic anemia
• Chronic infection (rare)

5. Leukemias & Lymphomas

Acute Leukemias

Acute Myeloid Leukemia (AML)

• Adults (median age 65)
• Auer rods (pathognomonic)
• MPO positive, Sudan Black B+
• M3 (APL): t(15;17), DIC risk

Acute Lymphoblastic Leukemia (ALL)

• Children (peak 2-5 years)
• TdT positive (marker)
• PAS positive (block pattern)
• t(9;22) Philadelphia = poor prognosis

Chronic Leukemias

Chronic Myeloid Leukemia (CML)

• Middle-aged adults
• Philadelphia chromosome t(9;22)
• BCR-ABL fusion gene
• Low LAP score
• Treated with Imatinib (Gleevec)

Chronic Lymphocytic Leukemia (CLL)

• Elderly (>60 years)
• Most common leukemia in adults
• Smudge cells on smear
• Often indolent course

6. Platelets & Disorders

Platelet Function

Adhesion: Platelets adhere to exposed collagen via vWF
Activation: Shape change, granule release (ADP, TXA2)
Aggregation: Platelets bind together via fibrinogen-GPIIb/IIIa
Plug formation: Primary hemostatic plug

Thrombocytopenia Causes

↓ Production

• Aplastic anemia
• Leukemia infiltration
• Chemotherapy
• B12/folate deficiency

↑ Destruction

• ITP (immune)
• TTP/HUS
• DIC
• Drug-induced (heparin)

Sequestration

• Splenomegaly
• Cirrhosis
• Up to 90% in enlarged spleen

7. Coagulation Cascade

Pathways

Intrinsic (aPTT)

XII → XI → IX → VIII → X

Contact activation; "inside" vessel

Extrinsic (PT)

III (TF) + VII → X

Tissue factor; "outside" vessel

Common

X → V → II → I (Fibrin)

Both pathways converge here

Coagulation Tests

Test	Normal	Monitors	Factors
PT	11-13 sec	Warfarin	VII, X, V, II, I
INR	0.9-1.1	Warfarin	Standardized PT
aPTT	25-35 sec	Heparin	XII, XI, IX, VIII, X, V, II, I
TT	14-19 sec	Fibrinogen	Fibrinogen → Fibrin

Vitamin K-Dependent Factors:

II, VII, IX, X (and Proteins C, S)

8. Hemostasis Disorders

Inherited Bleeding Disorders

Hemophilia A (Factor VIII)

• X-linked recessive (males)
• Most common hemophilia
• ↑ aPTT, normal PT
• Deep tissue/joint bleeding

Hemophilia B (Factor IX)

• X-linked recessive
• "Christmas disease"
• ↑ aPTT, normal PT
• Clinically identical to A

von Willebrand Disease

Most common inherited bleeding disorder
• vWF needed for platelet adhesion and carries Factor VIII
• ↑ Bleeding time, ↑ aPTT (mild), normal PT
• Mucocutaneous bleeding (epistaxis, menorrhagia)
• Treatment: DDAVP, vWF concentrate

DIC (Disseminated Intravascular Coagulation)

Causes: Sepsis, trauma, malignancy, obstetric complications
Lab findings: ↑ PT, ↑ aPTT, ↓ Platelets, ↓ Fibrinogen, ↑ D-dimer, schistocytes
Paradox: Both bleeding AND clotting occur simultaneously

Key Takeaways

✓MCV <80 = microcytic (iron deficiency), >100 = macrocytic (B12/folate)
✓Left shift = increased bands/immature cells = bacterial infection
✓Auer rods are pathognomonic for AML; TdT positive indicates ALL
✓PT monitors warfarin (extrinsic); aPTT monitors heparin (intrinsic)
✓Vitamin K-dependent factors: II, VII, IX, X

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