I get a lot of questions about Western Blot test results: Do I have Lyme?
The disease cannot be diagnosed by a blood test. The Western Blot test is one tool used to demonstrate that a patient has been exposed to Borrelia burdorferi. Period.
Testing for Lyme antibodies is much more complicated than testing for most other germs. Antibodies directed against most bacteria and viruses are determined by ELISA or IFA technology, and that it all that is generally required. The Western Blot was supposed to be a confirmation test used to validate a positive ELISA in the case of Lyme disease. Many of us who treat Lyme have found this to be inaccurate. The only other disease that I am aware of that uses this two tier approach is HIV. Some patients who test positive for HIV by the ELISA method are negative by the Western Blot method. These patients are false positive; they do not have HIV. Some patients who test positive by the WB method are ELISA negative and also do not have HIV. For the HIV test to provide accurate result the ELISA must be done first before the WB.
What is true for HIV testing is not true for Lyme testing. Nonetheless, many physicians cling steadfastly to this incorrect line of thinking.
A test is considered sensitive when it picks up all, or nearly all positive cases. Frequently, tests with high sensitivity also include some false positives. When this occurs the test is considered sensitive but not specific. A test is considered specific when a positive result is very accurate and can be relied upon for a diagnosis.
For many reasons, which have been discussed elsewhere, it has been shown that the current Lyme ELISA test is not sensitive. In other words it has many false negatives. This is why most physicians who treat a lot of Lyme disease skip the ELISA test and go right to the WB test.
It has been well established that seronegative(no antibodies) Lyme disease exists. One could debate how frequently this occurs, but in my experience it is quite frequent. This knowledge influences the interpretation of WB bands as will be discussed.
The spirochete has a lot of targets for antibody production. Areas on a germ which elicit the production of antibodies are called antigens. Antigenic regions on the bacteria are associated with the production of unique antibodies which target that specific antigenic region of the bacteria. In the WB test these are seen as bands which appear on the blot.
What is CDC positive? People are very confused about this. The CDC criteria for evaluating Lyme WB bands was created in 1994. Its purpose was epidemiological surveillance. It was never intended for use as or validated for use as a diagnostic tool. Those of us who look at Western Blots do our best to interpret the results based on our knowledge of what the bands represent. Since many patients are seronegative, the diagnosis of Lyme may be suggested when very few bands appear.
What is the IgeneX criteria? IgeneX has developed internal criteria which it reports as evidence of exposure to Bb. Basically if a patient shows two specific bands(in the same antibody class) the test is reported as positive.
The most commonly seen band is the 41 band. Most consider it sensitive but feel that it lacks specificity. I think the jury is still out on this one. It is not yet clear to me whether or not the presence of only this band can be used as supporting evidence of exposure to Bb. I don't think there are as many false positives as has been suggested by other authors. Both the CDC and IgeneX consider this band to be quite specific.
There are no standardized criteria for a positive Lyme Western Blot. This means that your doctor many interpret the results quite differently from other doctors. This includes LLMDS.
What we do know is that some of the bands are not very specific for Bb. I, like IgeneX tend to discount non-specific bands when viewing a report. When highly specific bands appear it is unlikely that their presence represents anything other than Bb exposure. Based on this thinking, many doctors may feel comfortable concluding that the test for Lyme is positive if few of these specific markers are identified on the WB test.
The very specific bands include: 93(region) 41,39,34,31 and 23. Some authors include the 18 band.
Whereas IgeneX will only call the test positive if the two specific WB bands are found in the same subclass of antibodies, IgG or IgM, this designation seems arbitrary and is of less importance to me. For example, If a patient has an IgG 93 band and IgM 23 band I feel comfortable that the patient result shows evidence of Lyme exposure.
In fact, the presence of a single, highly specific band(with the exception of the 41 band) may be taken as evidence that the patient has been exposed to Bb - a positive result. Again, it must be emphasized that there are no universally agreed upon criteria for the assessment of a positive or negative WB. Doctors who treat Lyme may all interpret these results through the lens of their own beliefs and experience and report differing conclusions.
The question then(at least regarding WB tests) is not doctor, do I have Lyme?
The question is, doctor is my Lyme test positive. First off, patients frequently ask: am I CDC positive. I then have to go through the process of explaining why this is not important. Ultimately I can only present patients with my interpretation of the results. This can end up being a bit unsatisfactory for the patient. Unfortunately, as is the case with most things "Lyme," answers to questions are frequently fuzzy. In the example given above, the 93 IgG and the 23 IgM are present. I would interpret this as positive result. There is no text or standard resource which patients can use to validate my interpretation. Ultimately it may come down to the doctor - patient relationship, and a patients comfort level with their doctor's interpretation. Patients should be aware of these complexities when requesting results from their doctor.
This is where the art of medicine trumps the science of medicine once more.