Two types of antibodies are detected in the Western blot test.

IgG antibodies are a sign of an older infection. IgM antibodies in contrast reflect a relatively recent infection.

IgM antibodies usually disappear after eight weeks post-exposure. 
IgG remains in the serum for a very long time. 

In the Western blot test there are three bands for IgM and 10 bands for IgG.

Here is the important part:

- You need to have 2 out of 3 for the positive IgM result

- Or you need to have 5 out of 10 for the positive IgG result. 

This marker is called Lyme Disease AB (IGG), Blot and is an aggregate marker for the ten IgG results. So if this marker is positive you have at least 5 out of 10 of the IgG markers positive.

Here is the 2nd important part when it comes to a diagnosis:

If a person doesn't have signs or symptoms of Lyme disease, then the person does not have Lyme disease as the definition of disease requires symptoms.

What could some of those symptoms be?

What are the symptoms of Lyme disease?

Lyme disease symptoms are wide-ranging, with more than a hundred different symptoms recorded. Symptoms can also change over time, as the bacteria spreads throughout the body. To make things more confusing, Lyme disease symptoms will also vary from patient-to-patient. Lyme disease can mimic hundreds of other conditions since its symptoms mirror many medical problems such as multiple sclerosis, arthritis, chronic fatigue syndrome or lupus, and is sometimes known as “The Great Imitator” because of this. 

Symptoms can play a key role in diagnosing Lyme disease. Due to the lack of an accurate diagnostic test, many patients are diagnosed based on a combination symptoms and diagnostic testing. This makes it extremely important for patients to keep track of all the symptoms they experience, to share with their healthcare provider. Lyme disease symptoms can vary based on stage of the disease (early, late, post-treatment, or chronic) and if other tick-borne infections are present and can change over time.

Symptoms in acute Lyme disease:

Acute Lyme disease (aka: early localized LD) occurs days to weeks after the initial tick bite and infection, in which the bacteria have not yet spread from the site of infection in the skin.

The most common symptoms in acute (aka: early localized) Lyme disease are the ones people are most familiar with. Because they are symptoms often shared with other illnesses, however, it’s important to recognize that they could mean Lyme and you should see a Lyme-treating physician right away.

- Erythema migrans rash or EM rash. This rash begins at the site of the tick bite about a week after the bite, and gradually expands.

Note: The center of the rash may clear, giving the rash the appearance of a “bulls-eye.” Rashes may take on many different shapes and not all rashes will have a bulls-eye appearance. There can be multiple rashes on the body. While a rash is characteristic of Lyme disease, many people will not develop a rash at all.

- Fever

- Fatigue

- Aches

- Chills

- Swollen lymph nodes

- Other flu-like symptoms

Symptoms in early disseminated Lyme disease:

Early disseminated Lyme disease occurs days to months after infection, in which the bacteria have begun to spread. There is a wide range of possible symptoms at this stage, including:

- Severe headaches and neck stiffness

- Arthritis, especially in the knees or other large joints

- Muscle aches and pains

- Heart palpitations or shortness of breath (Lyme carditis)

- Facial paralysis on one or both sides (also known as Bell’s palsy)

- Numbness or tingling in the hands or feet

- Extreme fatigue

Symptoms in late stage Lyme disease:

Late stage Lyme disease, which can include post-treatment, chronic, and neurological, occurs months to years after infection, in which the bacteria have spread throughout the body.

The symptoms of late disseminated disease are similar to those of early disseminated disease, but may be more extensive, more severe, and longer lasting. Late symptoms may also include:

- neurologic features including vertigo or dizziness,

- difficulty sleeping

- mental fogginess

- difficulty following conversations

- difficulty processing information

A blood test may be positive for several reasons: 

First, the positive test may indicate that the person was infected previously by the agent of Lyme disease and the immune system mounted a successful attack which resulted in the long-term production of antibodies against the agent of Lyme disease. That's why tests can stay positive for months to years, even when active infection is no longer present. We expect, however, that over time the ELISA titer should decrease in magnitude.

Second, a positive test may also indicate that there is a small amount of persistent infection that is continuing to partially stimulate the immune system. The residual organism may not be biologically active; i.e., it might be in a latent or dormant state and thus not causing any disease symptoms. In this case, the ELISA titer may stay elevated for long periods without a gradual decline.

Third, a positive test may be a false positive, especially if the positive test is only an ELISA. It is well known for example that concurrent viral infections (such as Epstein-Barr) may result in a false positive Lyme ELISA. If the positive test is an IgG Western blot or a C6 Lyme ELISA, it is very unlikely that either test would be falsely positive.

Fourth, a positive test may indicate that you did have some of the signs or symptoms of Lyme disease in the past but didn't recognize the problem as Lyme disease. You may have then been treated with antibiotics for another reason and this may have led to a resolution of the Lyme disease without your awareness of ever having had Lyme disease.