Lyme Disease Test Accuracy – IFA
The immunofluorescent assay (IFA) is often used as an initial screening tool for Lyme disease but most guidelines suggest that it is inferior to ELISA testing and that the latter should be used where possible. Several European studies have found IFA less sensitive in detecting antibodies to Borrelia bacteria in comparison to ELISA and Western blot testing. Lencáková, et al (2008) found that the immunoblot had a general sensitivity for IgG and IgM of 93.2% in their study, with the ELISA slightly less sensitive at 90.5% and the IFA significantly less sensitive at just 64.9%. Different proteins had slight variability in terms of sensitivity between the tests but IFA was inferior in all cases. An earlier study by Christova (2003) also found IFA to be less sensitive than ELISA identifying IgM antibodies to Borrelia burgdorferi in just 47% of the positive serum samples.
Improvements in sensitivity of the IFA test for Lyme disease have been achieved by careful selection of the antigens being tested against. This is particularly important in European cases of Lyme disease where B. afzelii, B. garinii, or B. burgdorferi may be the infectious agent responsible for symptoms. Specificity of IFA was found to be 89% in a study by Jovicić, et al (2003), in comparison to ELISA (93%), and immunoblot (96%). In earlier cases of Lyme disease it appeared that the sensitivity of IFA was just 36% however, in comparison to rates of 67% and 93% for ELISA and immunoblot respectively. Later stage Lyme disease led to better sensitivity for all measures at 72% for IFA, 80% for ELISA, and 94% for immunoblot.
ELISA Preferred for Lyme Disease Testing
Where ELISA testing is available this is preferable to IFA tests for Lyme disease as it has been shown to be consistently more sensitive and specific than IFA. However, despite a low level of sensitivity and specificity, IFA tests which return negative are still considered sufficient to discount further testing using Western blot methods. Many patients, and their physicians, will likely feel that further testing is worthwhile where symptoms of Lyme disease persist, and they may find that sending a serum sample to different laboratories leads to a positive IFA result from one and a negative or borderline result from the other due to subjectivity and higher sensitivity in later stages of infection with this particular test for Lyme disease.
Lencáková D, Fingerle V, Stefancíková A, Schulte-Spechtel U, Petko B, Schréter I, Wilske B. Evaluation of recombinant line immunoblot for detection of Lyme disease in Slovakia: comparison with two other immunoassays. Vector Borne Zoonotic Dis. 2008 Jun;8(3):381-90.
Christova I. Enzyme-linked immunosorbent assay, immunofluorescent assay, and recombinant immunoblotting in the serodiagnosis of early Lyme borreliosis. Int J Immunopathol Pharmacol. 2003 Sep-Dec;16(3):261-8.
Jovicić VLj, Grego EM, Lako BL, Ristović BM, Lepsanović ZA, Stajković NT. Improved serodiagnosis of early Lyme borreliosis: immunoblot with local Borrelia afzelii strain. APMIS. 2003 Nov;111(11):1053-9.
Cerar T, Ruzic-Sabljic E, Cimperman J, Strle F. Comparison of immunofluorescence assay (IFA) and LIAISON in patients with different clinical manifestations of Lyme borreliosis. Wien Klin Wochenschr. 2006 Nov;118(21-22):686-90.