Haematological tests are essential diagnostic tools used to assess the health of the blood and its components. They help identify anemia, infections, bleeding disorders, clotting abnormalities, immune conditions, leukemias, and other systemic diseases. Clinical pharmacists must understand these tests to interpret patient reports accurately, monitor drug effects, and support therapeutic decisions. Haematological investigations form a fundamental part of patient assessment in clinical and hospital settings.
Importance of Haematological Tests
- Detect blood disorders such as anemia, polycythemia, and leukemia.
- Monitor infection and inflammation.
- Assess clotting function and risk of bleeding.
- Guide therapy for conditions like anticoagulation and chemotherapy.
- Evaluate organ function and systemic disease progression.
Complete Blood Count (CBC)
CBC is the most commonly performed haematological test. It evaluates the three major cellular components of blood—red blood cells (RBCs), white blood cells (WBCs), and platelets.
1. Hemoglobin (Hb)
Hemoglobin is the protein responsible for carrying oxygen. Low Hb indicates anemia, while high Hb suggests dehydration, polycythemia, or chronic hypoxia.
2. Hematocrit (PCV)
Hematocrit represents the percentage of RBCs in whole blood. It provides insight into hydration status and RBC concentration.
3. Total RBC Count
RBC count helps detect anemia (low count) or polycythemia (high count). It should be interpreted along with Hb and hematocrit.
4. RBC Indices
- MCV (Mean Corpuscular Volume): Indicates red cell size; used to classify anemia as microcytic, normocytic, or macrocytic.
- MCH (Mean Corpuscular Hemoglobin): Measures hemoglobin amount per RBC.
- MCHC (Mean Corpuscular Hemoglobin Concentration): Reflects hemoglobin concentration in RBCs.
- RDW (Red Cell Distribution Width): Shows variation in RBC size, helpful in differentiating types of anemia.
White Blood Cell (WBC) Count
WBC count assesses the body’s immune response. Abnormal levels indicate infection, inflammation, allergic reactions, or blood cancers.
Differential Leukocyte Count (DLC)
DLC provides the percentage distribution of different WBC types:
- Neutrophils: Elevated in bacterial infections.
- Lymphocytes: Increased in viral infections.
- Monocytes: Elevated in chronic infections.
- Eosinophils: High levels seen in allergies and parasitic infections.
- Basophils: Increased in hypersensitivity reactions and certain leukemias.
Platelet Count
Platelets play a crucial role in clotting. Low platelet count (<150,000/µL) indicates thrombocytopenia, which may be caused by drugs, infections, or immune disorders. High platelet count suggests thrombocytosis, commonly seen in inflammation or myeloproliferative disorders.
Peripheral Smear Examination
A peripheral smear provides a microscopic view of blood cells. It helps identify abnormal RBC shapes, WBC morphology, immature cells, hemolysis, and clues to specific hematological conditions.
Findings in Peripheral Smear
- Microcytosis: Iron-deficiency anemia.
- Macrocytosis: Vitamin B12 or folate deficiency.
- Spherocytes: Hereditary spherocytosis.
- Burr cells: Renal disease.
- Blasts: Leukemia.
Erythrocyte Sedimentation Rate (ESR)
ESR measures the rate at which red blood cells settle in one hour. It is a nonspecific marker of inflammation.
Conditions with Elevated ESR
- Infections
- Autoimmune disorders
- Rheumatoid arthritis
- Malignancies
Reticulocyte Count
Reticulocytes are immature RBCs. Their count reflects bone marrow activity. High levels indicate increased RBC production (e.g., hemolysis), while low levels suggest bone marrow suppression.
Coagulation Profile
Coagulation tests assess the body’s ability to form clots and are essential for diagnosing bleeding disorders and monitoring anticoagulant therapy.
1. Prothrombin Time (PT)
PT measures the time it takes for blood to clot through the extrinsic pathway. It is prolonged in liver disease, vitamin K deficiency, and warfarin therapy.
2. International Normalized Ratio (INR)
INR standardizes PT values for warfarin monitoring. Target INR varies by clinical condition (e.g., 2–3 for atrial fibrillation).
3. Activated Partial Thromboplastin Time (aPTT)
aPTT evaluates the intrinsic pathway. It is prolonged in hemophilia, heparin therapy, and coagulation factor deficiencies.
4. Bleeding Time (BT)
BT assesses platelet function. Prolonged BT suggests platelet dysfunction or von Willebrand disease.
5. Clotting Time (CT)
CT measures the overall ability of blood to clot, though it is rarely used in modern practice.
Bone Marrow Examination
Bone marrow aspiration and biopsy are performed when blood tests suggest marrow dysfunction such as leukemia, aplastic anemia, or myelodysplasia.
Indications
- Unexplained anemia
- Persistent low or high blood counts
- Suspected leukemia or lymphoma
- Evaluation of marrow response to therapy
Clinical Applications of Haematological Tests
- Diagnosing anemia and classifying its type.
- Monitoring chemotherapy and its side effects.
- Detecting infections and immune responses.
- Screening for bleeding and clotting disorders.
- Guiding anticoagulant therapy using INR and aPTT.
- Evaluating bone marrow function in chronic diseases.
Drug-Induced Haematological Changes
Many medications can alter blood counts, making haematological monitoring essential in clinical settings.
- Bone marrow suppression: chemotherapy, chloramphenicol.
- Hemolysis: antimalarials in G6PD deficiency.
- Thrombocytopenia: heparin, antiepileptics.
- Leukopenia: clozapine, carbimazole.
Detailed Notes:
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