Definition 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, round glands found throughout the body that produce white blood cells. White blood cells fight invading foreign cells and micro-organisms such as bacteria. During infections, the infecting micro-organisms can be found in fluid from lymph nodes, which often become swollen. Fluid from infected lymph nodes is cultured and studied to determine the proper treatment.
How is the test performed? 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 anaesthetic. 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 recognising bacteria), looks at the culture to identify the bacteria causing the infection.
What is involved in preparation for the test? Specific instructions are available from the doctor.
What do the test results mean? Normally, no micro-organism will grow in culture from a sample of lymph fluid.
If micro-organisms grow in culture, it means an infection is present.
Author: David T. Moran, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 6/06/2005 Contributors Potential conflict of interest information for reviewers available on request
