Why You Can Have Lyme Even if You Test Negative
A negative Lyme disease test does not necessarily mean that you don't have Lyme disease.
Here are some reasons that your test might come back negative even if you have Lyme disease.
Why You Might Have Lyme Even if You Test Negative
First, understand that the ELISA and Western blot tests measure the levels and types of antibodies that your immune system makes against Lyme disease (see my hub on Lyme testing).
1) If you take the Lyme test too early in the course of the disease, you might not be making enough antibodies yet. The rate of positive results among people with Lyme disease rises from about 20-30% in the first 2-4 weeks to up to 80% by the fourth week. (NYT Health Guide). http://health.nytimes.com/health/guides/disease/lyme-disease/diagnosis.html
2) If you have taken or are currently taking antibiotics, your Lyme antibody levels might be too low to meet the criteria for a positive test result (NYT Health Guide). If you plan to start antibiotic therapy for something that might be Lyme disease, get a Lyme test first. http://health.nytimes.com/health/guides/disease/lyme-disease/diagnosis.html
3) Ironically, having a high bacterial load of Lyme bacteria might cause you to test negative. The more bacteria you have, the more of your antibodies will be stuck to bacteria, leaving fewer antibodies floating around to show up in a test.
4) If you are immunosuppressed, whether from immune-suppressing drugs or a disease, you might not be making enough antibodies for a positive result.
5) The cut-off level for the lab you are using might be high. You might have Lyme antibodies, but not enough to meet the criteria set by the lab that performs your test.
6) You might be producing Lyme antibodies, but not the "right" bands (or types of antibodies) for a positive result. Ask to see all the band results of your Western blot (see my upcoming hub about Lyme bands and CDC criteria).
And Vice Versa
On the other hand, you might not have Lyme disease even if you test negative.
You might test positive due to a previous, resolved case of Lyme disease or from similar infections such as relapsing fever or syphilis.
If you have tested negative even though you think you have Lyme disease:
1) Consider getting tested again in a few weeks.
2) Think about finding a Lyme-literate doctor.
3) Try other, more sensitive tests, such as the IGeneX or PCR tests (see my hub on Lyme testing).
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