American Board of Internal Medicine (ABIM) Certification Practice Exam

What indicates that Lyme arthritis can be excluded after how many months of symptoms with a negative Western blot IgG result?

1. 2 weeks

2. 1 month

3. 3 months

4. 6 weeks

The correct answer is: 1 month

The accurate timeframe for excluding Lyme arthritis when the Western blot IgG test is negative is one month. Generally, Lyme disease can manifest with various symptoms, including arthritis, and it's well understood that not every patient with Lyme disease will produce detectable IgG antibodies immediately after infection. The Western blot test, particularly for IgG, is most likely to yield positive results about four to six weeks after infection. If a patient has had symptoms consistent with Lyme disease, such as arthritis, for more than one month and has a negative IgG result on a Western blot, it becomes increasingly likely that Lyme disease is not the underlying cause of the symptoms. This timeframe helps clinicians establish a clearer understanding of the patient's condition and avoids unnecessary treatments grounded in the assumption that Lyme disease is still active when it is not.