BARTONELLA IFA

Results should always be interpreted together with clinical evaluation, epidemiological background, immune status, timing of sample collection and other diagnostic procedures.

Bartonella serology should not rely on a single result when recent infection is suspected. Paired acute and convalescent samples should be collected and tested in parallel whenever possible.

Samples collected very early in infection may not have detectable antibody levels. If clinical suspicion remains high, a second sample should be collected 14–21 days later to assess seroconversion or a significant antibody rise.

IgM may support recent infection, but it should be interpreted together with IgG results and clinical findings.

IgG titres may remain detectable after infection and do not always indicate active disease.

IFA titres of 1:64 to 1:256 are suggestive but not diagnostic of Bartonella infection. Titres of 1:512 with compatible clinical manifestations are strongly suggestive of disease.

Cross-reactivity between Bartonella henselae and Bartonella quintana has been reported. Positive results for both species may occur, and species orientation should consider the relative titres.

In the dual Bartonella henselae / Bartonella quintana IFA, one species should be considered predominant only when its titre is at least twice the titre observed for the other species.

A negative result in immunosuppressed patients does not always exclude infection, since antibody responses may be weak, delayed or absent.

Interferences or cross-reactivity may occur in some samples, including samples positive for antinuclear antibodies, rheumatoid factor, Coxiella burnetii, Brucella abortus or Chlamydophila pneumoniae, depending on the assay.