Peripheral Blood Morphology

Function and Overview

Peripheral Blood Morphology, often referred to as a peripheral blood smear, is a diagnostic procedure where a drop of blood is spread thinly onto a glass slide, stained, and examined under a microscope. This test provides a detailed visual assessment of the three primary components of blood: red blood cells (RBCs), white blood cells (WBCs), and platelets. While automated counters provide numbers, morphology provides the "story" behind those numbers, revealing abnormalities in cell size, shape, and internal structures.

Why It Is Ordered

This test is rarely a screening tool; it is usually ordered as a follow-up to an abnormal Complete Blood Count (CBC). Clinical indications include:

• Unexplained Anemia: To distinguish between iron deficiency (microcytic), B12 deficiency (macrocytic), or hemolytic anemia (presence of schistocytes).
• Leukemia Suspicion: To identify 'blast' cells or immature white cells that suggest bone marrow failure or malignancy.
• Thrombocytopenia: To rule out "pseudothrombocytopenia" (platelet clumping) or to identify giant platelets.
• Infection and Parasites: To detect blood-borne parasites like Malaria or Babesia, or to see 'toxic granulation' in neutrophils during severe sepsis.

Associated Conditions

Abnormal morphology can point to a wide range of conditions. For instance, Sickle Cell Disease is identified by crescent-shaped RBCs. Target cells may indicate liver disease or Thalassemia. Schistocytes (fragmented cells) are critical markers for medical emergencies like Thrombotic Thrombocytopenic Purpura (TTP) or Disseminated Intravascular Coagulation (DIC). Identifying these morphological markers allows for rapid, life-saving interventions that automated machines might miss.