Dr. Paul McKeown:

Perhaps I can be of assistance. I have read the 1991 study of blood donors. It looked at the background population. As I stated earlier, 25% of those tested in the New Forest study were positive. The 1991 study sampled blood donors, which is a reasonable proxy for the background population. As the results from the NVRL originate with people who attended a doctor because of suspected Lyme disease or because they had been bitten by a tick, one would expect the positive test results to be higher. That probably explains the difference between the figures.