This is a laboratory test performed on fluid that has been taken from a lymph node. The test is usually done to see if a specific infection is present. Lymph nodes are small, oval-shaped glands found throughout the body that contain white blood cells. White blood cells fight invading foreign cells and microorganisms such as bacteria.
Fluid from the swollen lymph node is removed by a technique called needle aspiration. The lymph node to be tested is first identified. The skin is then cleaned with an antiseptic and injected with local anesthetic. When the skin is numb, the needle is inserted through the skin into the lymph node and a sample of fluid is removed. The fluid is then taken to the laboratory where it is grown in culture. After growing for a few days, a microbiologist (a specialist in recognizing bacteria), looks at the culture to identify the bacteria causing the infection.
Specific instructions are available from the healthcare professional.
Normally, no microorganism will grow in culture from a sample of lymph fluid. If microorganisms grow in culture, it means that an infection is present.