Evaluation of bacteriological serodiagnostics in patients with undifferentiated arthritis
Part III. Immunoenzymatic method (ELISA) as a screening test in serodiagnosis of joint inflammation of suspected B. burgdorferi aetiology: cross-reactivity of antibodies to B. burgdorferi with S. enteritidis, S. typhimurium, Y. enterocolitica O3 and Ch. trachomatis

Serum antibodies to Borrelia burgdorferi in 1850 cases of
patients hospitalized in the Institute of Rheumatology, consulted by physicians in Outpatient Clinics and also ordered by other medical units, were done in the years 2004-2006.

As a screening test, the ELISA method was applied for indication of antibodies IgG and IgM class against B. burgdorferi, and presence of these antibodies may suggest the infectious aetiology of analyzed unclassified joint inflammation.

The majority of the ordered tests (over 60% of all orders) in cases of children and teenagers (hospitalized in the Institute of Rheumatology) originated from the Paediatric Clinic and Paediatric Outpatient Clinic, and there was no correlation (relation) between ordered amount of assays and number of positive results (about 15%) of all ordered (requested) tests. Most frequently (in about 30% of tested samples) these antibodies are confirmed (independently of Ig-s class) in the sera of patients originating from Adult and Children Outpatient Clinics and also
in the sera of patients suffering cardiomyopathy, in which (in cardiomyobiopsics) some kinds of spirochetes were discovered (done as part of scientific cooperation with the Department of Pathological Anatomy).

Assessed antibodies were most frequently IgM class (66.2%), only rarely IgG class (around 25%), and only in 9% both classes. These results may be considered as an early stage of infection with joint involvement in the majority of patients seropositive for anti-Borrelia burgdorferi antibodies.

We also observed a high cross-reactivity (around 25%) with antigens of other bacteria such as: Salmonella enteritidis, Salmonella typhimurium, Yersinia enterocolitica O3 and Chlamydia trachomatis and this phenomenon of cross-reactivity indicates very limited value of the screening method, because all positive results should be confirmed by a specific Western blot method.
At the same time, co-appearance of antibodies to other bacteria suggests co-infection or possibly former infection, especially in cases with presence of antibodies to two different classes directed at different microbes (bacteria).

The obtained results may be considered as proof that in any case seropositivity should be necessarily interpreted with regard to the clinical studies of particular patients and also differential diagnosis, taking into consideration other diseases giving
a similar clinical picture, as in borreliosis.