Haemogram

Overview

Haemogram, also known as Complete Blood Count, is one of the most commonly requested laboratory tests and provides a quantitative assessment of the cellular components of blood. It evaluates red blood cells, white blood cells, and platelets, offering a snapshot of overall health. The test broadly screens for diseases and infections and serves as a fundamental tool in diagnosing hematological disorders such as anemia, leukemia, bone marrow suppression, and blood parasitic infections, including malaria and leishmaniasis. It is routinely advised in both symptomatic and asymptomatic individuals as a basic clinical screening investigation.

Symptoms

Haemogram is commonly ordered irrespective of the presence of overt disease because many conditions may be detected incidentally. It helps identify unsuspected anemia, infection, or hematological abnormalities even before clinical symptoms become evident. It is often performed before consulting a specialist and is frequently combined with routine urine examination as an initial evaluation tool. Abnormal values in red cells may suggest fatigue related to anemia, altered white cell counts may indicate infection or immune response, and platelet abnormalities may correlate with bleeding or clotting tendencies.

Causes

The test measures hemoglobin concentration, red blood cell count, total white blood cell count, differential white cell count, and platelet count. Red blood cells are responsible for oxygen transport and removal of carbon dioxide. Hemoglobin carries oxygen throughout the body. White blood cells include neutrophils, lymphocytes, eosinophils, monocytes, and basophils, each playing a role in immune defense against bacteria, viruses, parasites, and allergic responses. Platelets are essential for blood clot formation and hemostasis. Additional parameters such as MCV, MCH, and MCHC provide information about red cell size and hemoglobin content. Absolute counts including ANC, ALC, AEC, AMC, and ABC offer further insight into immune status. Other platelet indices such as PDW, PCT, MPV, and parameters like nucleated red blood cells contribute to detailed hematological evaluation. Sample collection requires two to three milliliters of blood in an EDTA tube, and prompt processing is recommended. Modern automated analyzers use electrical impedance for cell counting, flow cytometry for differential analysis, and photometry for hemoglobin estimation.

Risk Factors

Variations in haemogram parameters may arise from infections, inflammatory conditions, hematological malignancies, bone marrow disorders, parasitic infestations, and systemic illnesses. Reference ranges vary according to age, sex, ethnicity, and altitude. Pregnancy and certain medications may alter values. Technical issues such as clotted samples, improper storage, hemolysis, delayed processing, and automation artifacts like pseudothrombocytopenia can affect accuracy. A normal complete blood count does not rule out all diseases and must always be interpreted in clinical context. Peripheral smear examination is often required for confirmation of abnormal findings.

Prevention

Routine haemogram testing aids early detection of hematological disorders and infections. Timely processing of samples minimizes technical errors. Correlating laboratory findings with clinical history and physical examination ensures accurate diagnosis. Awareness of factors influencing reference ranges improves interpretation. Confirmation with peripheral smear review enhances diagnostic reliability. As a widely accessible and comprehensive screening tool, haemogram plays a critical role in preventive health evaluation and disease monitoring.