Understanding Your Laboratory Test: A Patient's Guide to Testing, Sample Collection, and Results

This laboratory test is a common diagnostic procedure that helps your doctor evaluate your overall health, screen for certain medical conditions, and monitor how well a current treatment plan is working over time.

The Borrelia burgdorferi 28kD IgG Antibody test is a specialized laboratory test that detects IgG (immunoglobulin G) antibodies specifically targeting the 28kD protein of Borrelia burgdorferi, the bacterium that causes Lyme disease. This test is performed on synovial fluid, which is the lubricating fluid found in joints. The immunoblot (also known as Western blot) technique is used to identify these specific antibodies, providing detailed information about whether your immune system has responded to the Lyme disease bacteria.

A trained healthcare professional will collect your sample, usually through a simple blood draw from a vein in your arm or occasionally through a urine collection, and the entire process typically takes only a few minutes.

Synovial fluid is collected from your joint through a procedure called arthrocentesis (joint aspiration). A healthcare provider will clean the skin over the affected joint, typically the knee, and insert a thin needle to withdraw a small amount of fluid. You may feel some discomfort or pressure during the procedure. The fluid is then sent to a laboratory for analysis. After the procedure, you may experience temporary soreness or swelling at the puncture site.

Your results are compared against established reference ranges, and values that fall outside the normal range may suggest an underlying condition, although only your healthcare provider can interpret what the numbers mean for your specific situation.

A positive result means that IgG antibodies against the 28kD protein of Borrelia burgdorferi were detected in your synovial fluid. This indicates that you have or had a Lyme disease infection that is affecting or has affected your joint—specifically, Lyme arthritis. A negative result does not completely rule out Lyme arthritis, as antibody levels can vary depending on the stage of infection and individual immune response. Your healthcare provider will interpret these results together with your clinical symptoms, history of tick exposure, and other test results.

This test plays a key role in the early detection of disease, in guiding treatment decisions, and in tracking your progress, which is why your doctor may order it during a routine checkup or before starting a new medication.

This test is particularly valuable because the 28kD protein is specific to Borrelia burgdorferi, meaning it's unlikely to produce positive results from other infections or conditions. Testing joint fluid directly can provide more definitive evidence of joint involvement when blood tests are inconclusive or when patients have persistent joint symptoms despite treatment. This helps your doctor make an accurate diagnosis and recommend the appropriate treatment plan.