What is the efficacy of indirect fluorescence assay (IFA) testing for the diagnosis of cat scratch disease (CSD)?

Updated: Feb 16, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
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IFA testing for Bartonella is quite variable, as many different tests are available; test sensitivity may be as low as 53% but is up to 100% in some series, with a specificity of 98%. About 84% of patients have positive titers within 1-2 weeks of clinical CSD, and 16% develop positive titers 4-8 weeks later.

Accuracy of IFA can be improved by concurrent use of both immunoglobulin G (IgG) and immunoglobulin M (IgM) testing. [55] Specificity of IgM and IgG testing ranges from 88-98% and 50-62%, respectively. Most populations have low (2-6%) background seropositivity rates, limiting false-positive test results. The IFA shows cross-reactivity between Bartonella species, Epstein-Barr virus, cytomegalovirus, Toxoplasma gondii, and Streptococcus pyogenes. [56]

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