B. burgdorferi spirochetes are affixed to glass slides and usually a fluorescent-conjugated goat antihuman immunoglobulin of either IgM or IgG specificity is used (
20). 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 (
21,
22). Magnarelli et al (
23,
24) and Mitchell et al (
20) supported IFA if used in conjunction with a clinical evaluation. Mitchell's study with the IgM IFA showed excellent specificity and no observed cross-reactivity with infectious mononucleosis (n = 20), rheumatoid arthritis (n = 19), systemic lupus (n = 22), syphilis (n = 13), streptococcal sequelae (n = 20) or healthy subjects. Mitchell related the success of this test to the quality of the substrate slides and the level of experience of the technologists, and concludes that IFA microscopy becomes less subjective with experience.