Joint fluid gram stain

Alternative names:

gram stain of joint fluid

How the test is performed:

Fluid is aspirated with a needle inserted into a joint. A sample called a smear from the fluid is applied in a very thin layer to a microscope slide. The specimen is stained with a violet stain known as a gram stain and then examined under the microscope for the presence of bacteria. The color, number, and morphologic appearance of the cells helps make it possible to identify the genus (type) of the organism present.

How to prepare for the test:

Adult:
There is no special preparation for the test. It may be performed in the health care provider's office.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How the test will feel:

The joint is cleansed with an anti-bacterial soap. An anesthetic may be injected into the joint, and a stinging sensation may be felt. A needle is then inserted into the joint, and a small amount of fluid is withdrawn into a syringe. Pressure and pain in the joint may be present.

Why the test is performed:

The test is performed for unexplained swelling, joint pain, and inflammation of a joint or suspected joint infection.