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How do blood tests help doctors detect blood diseases?

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blood disease Peripheral blood smear revealing histopathologic features indicative of a blast crisis in a case of chronic myelogenous leukemia (CML). Blast crisis occurs when one-fifth to one-third of the cells in the blood or bone marrow are immature blood cells, or blast cells. This phase of CML is characterized by fever, weakness, and an enlarged spleen.

Blood tests are essential diagnostic tools that allow physicians to identify blood diseases and other systemic conditions by measuring various cellular and chemical constituents.12

Cellular Analysis

A complete blood count (CBC) is a primary test that quantifies red blood cells, white blood cells, and platelets. Automated analyzers detect these cells by measuring changes in electrical resistance as they pass through a narrow aperture. Additionally, microscopic examination of stained blood films allows doctors to observe abnormalities in cell size, shape, and color, which can indicate conditions like iron-deficiency anemia or the presence of parasites such as in malaria.312

Chemical and Immunologic Testing

Chemical analyses of plasma or serum measure substances like glucose, urea, enzymes, and hormones. These tests help diagnose non-blood disorders, such as diabetes or liver disease, by detecting abnormal concentrations of these constituents. Furthermore, immunologic studies, including antibody detection and cross-matching, are critical for safe transfusions and identifying infectious diseases.12