Borrelia burgdorferi IgG Antibody, Western Blot, Synovial Fluid (Lyme Disease Arthritis)

What is this test?

This test, whose full name is the Borrelia burgdorferi IgG antibody Western blot of synovial fluid, is a laboratory test used to diagnose Lyme arthritis. Borrelia burgdorferi is the bacterium that causes Lyme disease, and it is spread through the bite of an infected tick. When the bacteria infect a joint, the immune system produces specific IgG antibodies to fight the infection. This test uses a technique called Western blotting (also known as immunoblotting) to detect the presence of these antibodies, and it is an important confirmatory tool in the diagnosis of Lyme disease.

Why do I need this test?

Your doctor may recommend this test if you have been bitten by a tick or have symptoms related to Lyme disease, such as an expanding red rash (erythema migrans) or painful, swollen joints. This test is usually ordered after a positive ELISA screening test to confirm whether specific Lyme disease antibodies are present. Testing joint fluid is especially useful when Lyme arthritis is suspected, because it helps your doctor tell it apart from arthritis caused by other conditions.

What should I know before the test?

Before your joint fluid sample is collected, tell your doctor about all the medicines you take, especially blood thinners (anticoagulants) or immunosuppressants. Keep the collection site clean on the day of the procedure. Let your doctor know in advance if you have a tendency to bleed, an infected joint, or broken skin near the site. The collection may cause brief discomfort, and your doctor can use a local anesthetic to reduce the pain.

How are test results interpreted?

A Western blot shows the results of several different protein bands. A positive result means that IgG antibodies specific to Borrelia burgdorferi were detected, which suggests a Lyme disease infection. A negative result means that no specific antibodies were found, but it does not completely rule out infection, because an early infection may not yet have produced enough antibodies to detect. Your doctor must interpret the result together with your clinical symptoms, your history of possible tick exposure (such as a tick bite in an area where Lyme disease is common), and the findings of other tests.