No, it's not powerful at all. It's used as a screening to see who will be 'allowed' to get tested by the Western Blot by many labs - but not Igenex. Honestly, I'm a little confused as to why they even use it.
IFA stands for Indirect fluorescent antibody. ". Tests for Lyme disease using IFA have received mixed reviews and some authors believe that the interpretations of IFA assays are overly subjective and that the tests are either functionally insensitive for Lyme-specific antibodies or display considerable cross-reactions with antibodies to other spirochetal organisms."www.igenex.com/labtest.htm
The ELISA (Enzyme-linked immunosorbant assay)- "most are inadequate as a screening test because they were not designed by the manufacturers to be sensitive at the 95% level, which is required for screening."
"The goal for a new generation of ELISAs should be sensitivity for the more unique and specific B. burgdorferi antigens that are visualized in the Western blot." http://www.igenex.com/labtest.htm
The fact that you got a positive test using it says a lot!