Blood is drawn from a vein on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
For an infant or young child, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
An antibody defends the body against bacteria, viruses, fungus, or other foreign bodies (antigens). Microorganism can stimulate the body to produce these antibodies during active infection. Antibody production increases during the course of infection.
In the initial stage of an illness, little antibody may be detected. For this reason, serology tests (tests performed on serum, the fluid portion of blood that contains antibodies) are often repeated 10 days to 2 weeks or more after the initial sample.
In the laboratory, the antibodies react with antigens in specific ways that can be used to confirm the identity of a microorganism. There are several serology techniques that can be used depending on the suspected antibodies. Serology techniques include agglutination, precipitation, complement-fixation, fluorescent antibodies, and others.
| 
