BLOOD ANALYSIS

laboratory examination of a sample of blood to obtain information on its physical and chemical properties and on its components. Hundreds of hematological tests and procedures have been developed, and many can be carried out simultaneously on one sample of blood with such instruments as autoanalyzers. Blood analysis includes the following areas of study: (1) determination of the number of red and white blood cells in the blood, together with the volume, sedimentation rate, and hemoglobin concentration of the red blood cells (see blood count); (2) classification of the blood according to specific red-blood-cell antigens, or blood groups (see blood typing); (3) elucidation of the shape and structural details of blood cells; (4) study of the structure of hemoglobin and other blood proteins; (5) determination of the activity of various enzymes, or protein catalysts, that are either associated with the blood cells or are found free in the blood plasma; (6) study of blood chemistry. Other properties of blood that may be included in an analysis are total volume, circulation time, viscosity, clotting time and clotting abnormalities, acidity (pH), and clearance rate of various substances (see kidney function test). Blood analysis is commonly carried out on a sample of blood drawn from the vein of the arm, the finger, or the earlobe; in some cases, the blood cells of the bone marrow may also be examined. In addition to the wide variety of procedures devised for the study of normal blood constituents, there are also special tests based on the presence in the blood of substances characteristic of specific infections, such as the Wassermann reaction in the case of syphilis (q.v.). See also serological test.