Dr. Bartley Cryan:

Other tests are available. An activated lymphocyte test is available and is performed by some laboratories, particularly in Germany. One of the previous speakers set great store by this test but much of the medical literature does not concur with his conclusions. In some of the literature it is found to be much less sensitive and specific when compared to ELISA testing. In any case, the activated lymphocyte test looks at different versions of the same thing. One is not directly looking for the organism, which is what one would like to do, but at the body's response. The activated lymphocyte test looks at a cellular response, whereas the ELISA test looks at an antibody response. The latter approach is a very common way of dealing with infections, usually viral infections because they are hard to grow.