IgM and IgG Antibody Line Blot Test

This blood test checks for IgM and IgG antibodies that your immune system may produce in response to an infection. Using a laboratory method called a line blot, it helps your doctor find out whether you have been exposed to certain germs and, based on the antibody type detected, whether the exposure may be recent or happened in the past.

The Borrelia afzelii, burgdorferi, and garinii IgG and IgM panel is a blood test that uses line blot technology to detect antibodies your immune system produces in response to three different species of Borrelia bacteria that cause Lyme disease. These bacteria are transmitted through the bite of infected blacklegged ticks (Ixodes scapularis and Ixodes pacificus in the United States; Ixodes ricinus in Europe).

In a line blot, specific proteins from the germs being tested are placed as separate lines on a thin strip. Your blood sample is washed across the strip, and any antibodies present attach to the lines they recognize. A chemical reaction then highlights the matched lines, and the laboratory reads this pattern to determine whether IgM or IgG antibodies are present.

The line blot test is a highly specific laboratory technique. After your blood is drawn, the serum (the liquid part of blood) is mixed with test strips that contain purified Borrelia antigens arranged in lines. If your blood contains specific antibodies (IgM or IgG) against these antigens, they will bind to the strips, producing visible lines that indicate a positive result. This method is more specific than initial screening tests and helps confirm whether a positive screening result represents true Lyme disease infection.

IgM and IgG are two kinds of antibodies made by your immune system. IgM usually appears first, within days to a few weeks after an infection begins, and may point to a recent or active infection. IgG develops more gradually and can remain in your blood for months or years, so it often reflects a past infection, a long-standing one, or lasting immune memory.

IgM antibodies are produced first, typically within 1-2 weeks after infection. A positive IgM result suggests an early or recent infection. IgG antibodies develop later, usually within 4-6 weeks, and can remain in your blood for months or years. A positive IgG may indicate a later stage of infection or past exposure to the bacteria. Your healthcare provider will interpret both results together with your clinical symptoms to determine the stage of infection.

Preparation for this test is usually simple, and you typically do not need to fast beforehand. Your doctor may give you specific instructions, such as temporarily pausing certain medications like antibiotics or immune-suppressing drugs, so tell the staff about everything you take. Staying well hydrated can also make the blood draw easier and more comfortable.

No special preparation is needed for this blood test. You can eat and drink normally before having your blood drawn. Simply inform your healthcare provider of any medications you are taking, as some conditions or treatments may affect your immune response and test results.

Your results are usually reported separately for IgM and IgG as positive, negative, or indeterminate. A positive IgM may suggest a recent infection, while a positive IgG often indicates a past or ongoing one. Because some people without symptoms can show weak positive bands, your doctor will interpret the full pattern along with your symptoms, history, and any other test results before advising next steps.

Test results are reported as positive, negative, or indeterminate for each antibody type (IgM and IgG) against each Borrelia species. A positive result indicates that antibodies were detected. However, a positive result does not always mean you have active Lyme disease—it may indicate past exposure. A negative result does not completely rule out Lyme disease, especially if you have recent symptoms, as antibodies may not yet have developed. Your healthcare provider will interpret results in the context of your symptoms, exposure history, and when you may have been bitten.