Pregnancy SmartSite^TM

• Home
• Email
• Site Map
• Contact

• Normal Pregnancy
• Labor & Delivery
• Complications
• After Your Child Is Born

Normal Pregnancy

Staying Healthy

Alcohol and pregnancy Managing your weight gain in pregnancy Steps to take before you get pregnant When you need to gain more weight during pregnancy

What to expect during pregnancy

Aches and pains during pregnancy Choosing the right practitioner Common symptoms during pregnancy Hyperemesis Gravidarum Morning sickness Pregnancy and travel Pregnancy and work Problems sleeping during pregnancy Skin and hair changes during pregnancy Teenage pregnancy

Preparing to go home with your baby

Cribs and crib safety Eat right during pregnancy Preparing your other children

Visits and Tests

Amniocentesis Chorionic villus sampling Genetic counseling before pregnancy Glucose tolerance test-pregnancy Monitoring your baby before labor Nuchal translucency Prenatal care in your first trimester Prenatal care in your second trimester Prenatal care in your third trimester

Joint fluid Gram stain

Definition

Joint fluid Gram stain is a lab test to identify bacteria in a sample of joint fluid using a special series of stains (colors). The Gram stain method is one of the most commonly used ways to quickly diagnose bacterial infections.

How the Test is Performed

A sample of joint fluid is needed. This may be done in your health care provider's office using a needle, or during an operating room procedure. Removing the sample is called joint fluid aspiration.

The fluid sample is sent to a lab where a drop of fluid is spread in a very thin layer onto a microscope slide. This is called a smear. Several different colored stains are applied to the sample. The lab team member will look at the stained smear under a microscope to see if bacteria are present. The color, size, and shape of the cells help identify the bacteria.

How to Prepare for the Test

Your provider will tell you how to prepare for the procedure. No special preparation is needed. But, tell your provider if you're taking a blood thinner, such as aspirin, warfarin (Coumadin) or clopidogrel (Plavix). These medicines can affect test results or your ability to take the test.

How the Test will Feel

Sometimes, your provider will first inject numbing medicine into the skin with a small needle, which may sting. A larger needle is then used to draw out the synovial fluid.

This test may also cause some discomfort if the tip of the needle touches bone. The procedure usually lasts less than 1 to 2 minutes.

Why the Test is Performed

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

Normal Results

A normal result means no bacteria are present on the Gram stain. Other tests may be done to help diagnose the problem.

What Abnormal Results Mean

Abnormal results mean bacteria were seen on the Gram stain. This may be a sign of a joint infection, for example, gonococcal arthritis due to bacteria called Neisseria gonorrhoeae or arthritis due to bacteria called Staphylococcus aureus.

Risks

Risks of this test include:

• Infection of the joint -- unusual, but more common with repeated aspirations

• Bleeding into the joint space

References

Karcher DS, McPherson RA. Cerebrospinal, synovial, serous body fluids, and alternative specimens. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 30.

O'Neil L, Tanner S, El-Gabalawy HS. Synovial fluid analyses, synovial biopsy, and synovial pathology. In: Firestein GS, McInnes IB, Koretzky GA, Mikuls TR, Neogi T, O'Dell JR, eds. Firestein & Kelley's Textbook of Rheumatology. 12th ed. Philadelphia, PA: Elsevier; 2025:chap 53.

Review Date: 10/11/2024

Reviewed By: Frank D. Brodkey, MD, FCCM, Associate Professor, Section of Pulmonary and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.