Hematology tests are essential for diagnosing and monitoring a wide range of conditions, including anemia, infections, clotting disorders, and blood cancers. These tests evaluate components of blood such as red blood cells (RBCs), white blood cells (WBCs), platelets, hemoglobin, and coagulation factors.
1. Complete Blood Count (CBC)
The CBC is one of the most frequently ordered hematology tests and provides an overview of the cellular components of blood.
Key Parameters and Interpretation
| Parameter | Normal Range | Clinical Significance |
|---|---|---|
| Hemoglobin (Hb) | Male: 13.8–17.2 g/dL Female: 12.1–15.1 g/dL | Low: Anemia, blood loss, chronic disease High: Polycythemia, dehydration |
| Hematocrit (Hct) | Male: 40.7–50.3% Female: 36.1–44.3% | Low: Anemia, fluid overload High: Dehydration, polycythemia |
| Red Blood Cell Count (RBC) | Male: 4.7–6.1 million/µL Female: 4.2–5.4 million/µL | Low: Anemia, bone marrow suppression High: Polycythemia, hypoxia |
| White Blood Cell Count (WBC) | 4,500–11,000 cells/µL | Low: Leukopenia (viral infections, bone marrow failure) High: Leukocytosis (infection, inflammation, leukemia) |
| Platelet Count (PLT) | 150,000–450,000/µL | Low: Thrombocytopenia (bleeding disorders, immune conditions) High: Thrombocytosis (myeloproliferative disorders, inflammation) |
| Mean Corpuscular Volume (MCV) | 80–100 fL | Low: Microcytic anemia (iron deficiency, thalassemia) High: Macrocytic anemia (B12/folate deficiency, liver disease) |
| Mean Corpuscular Hemoglobin (MCH) | 27–33 pg | Low: Hypochromic anemia High: Hyperchromic anemia |
| Mean Corpuscular Hemoglobin Concentration (MCHC) | 32–36 g/dL | Low: Hypochromia (iron deficiency) High: Spherocytosis, autoimmune hemolysis |
| Red Cell Distribution Width (RDW) | 11.5–14.5% | High: Anisocytosis (iron deficiency, B12/folate deficiency) |
Clinical Applications of CBC
- Infections & Inflammation: Elevated WBCs indicate bacterial infections; low WBCs suggest viral infections or immune suppression.
- Anemia Classification:
- Microcytic (MCV < 80 fL): Iron deficiency, thalassemia
- Normocytic (MCV 80–100 fL): Acute blood loss, chronic disease anemia
- Macrocytic (MCV > 100 fL): B12/folate deficiency, alcohol-related disorders
- Bone Marrow Disorders: Abnormal counts may indicate leukemia, myelodysplastic syndromes, or marrow suppression.
2. Peripheral Blood Smear
A peripheral smear provides a microscopic examination of blood cells, helping to diagnose hematologic disorders.
Key Findings in Peripheral Smear
| Finding | Possible Diagnosis |
|---|---|
| Microcytosis, hypochromia | Iron deficiency anemia, thalassemia |
| Macrocytosis | B12/folate deficiency, liver disease |
| Spherocytes | Hereditary spherocytosis, autoimmune hemolytic anemia |
| Schistocytes (Fragmented RBCs) | Hemolytic anemia, DIC, TTP |
| Target Cells | Liver disease, thalassemia |
| Acanthocytes | Liver disease, abetalipoproteinemia |
| Howell-Jolly Bodies | Post-splenectomy, megaloblastic anemia |
| Dohle Bodies (in WBCs) | Severe infection, burns |
| Toxic Granulation (in WBCs) | Sepsis, inflammation |
3. Coagulation Tests
Coagulation studies assess blood clotting disorders such as hemophilia, disseminated intravascular coagulation (DIC), and liver dysfunction.
Common Coagulation Tests & Interpretation
| Test | Normal Range | Clinical Significance |
|---|---|---|
| Prothrombin Time (PT) | 10–13 seconds | Prolonged in liver disease, warfarin use, vitamin K deficiency |
| International Normalized Ratio (INR) | 0.8–1.2 (normal), 2–3 (on anticoagulants) | High: Bleeding risk Low: Clotting risk |
| Activated Partial Thromboplastin Time (aPTT) | 25–35 seconds | Prolonged in hemophilia, heparin therapy, DIC |
| Fibrinogen | 200–400 mg/dL | Low: DIC, liver disease High: Inflammation, pregnancy |
| D-dimer | <500 ng/mL | High: DVT, PE, DIC |
4. Bone Marrow Aspiration & Biopsy
Used for diagnosing:
- Leukemia, lymphoma
- Aplastic anemia
- Myelodysplastic syndromes
- Bone marrow metastases
Findings include abnormal blasts (leukemia), increased fibrosis (myelofibrosis), or hypercellularity (polycythemia vera).
5. Advanced Hematology Tests
These specialized tests are used for further investigation:
| Test | Purpose |
|---|---|
| Hemoglobin Electrophoresis | Diagnoses sickle cell disease, thalassemias |
| Reticulocyte Count | Evaluates bone marrow activity (high in hemolysis, low in marrow failure) |
| Flow Cytometry | Used in leukemia/lymphoma diagnosis |
| JAK2 Mutation Test | Diagnoses myeloproliferative disorders (polycythemia vera) |
| G6PD Enzyme Test | Diagnoses G6PD deficiency (hemolysis triggers) |
| Iron Studies (Ferritin, TIBC, Serum Iron) | Differentiates types of anemia |