Brucellosis 2003 proceedings - PHIDIAS

Short Oral Communications
Human brucellosis
15 minutes by visual inspection for staining of the antigen line in the test window of
the assay device. A positive result is consistent with brucellosis. The relative
expression of specific IgM and IgG antibodies depends on the stage of illness.
Therefore the two flow assays should be used as complementary tests. The Rose
Bengal test may be used as a screening test. The sensitivity as calculated for the
initial serum sample collected at the time of first diagnosis from patients with
confirmed brucellosis presented at different hospitals in Spain was 96%.
Approximately 75% had specific IgM antibodies and 86% had specific IgG antibodies.
The sensitivity for patients with acute or with persistent brucellosis was equally high.
Testing of samples collected from patients with brucellosis from endemic areas have
confirmed the high sensitivity and specificity. These results combined with the
simplicity of the assay procedure make the tests ideal for use in medical facilities that
lack appropriate diagnostic facilities or staff to perform the more complex standard
diagnostic tests. The tests also are suitable for use in the field and may be performed
on a drop of blood collected by fingerprick.
HO3- INTERFERENCE OF RHEUMATOID FACTOR IN THE IgM-BASED
SEROLOGICAL DIAGNOSE OF HUMAN BRUCELLOSIS.
R. Díaz 1 , H. Smits 2 , T.H. Abdoel 2 , M. Rubio 1 , J. Ariza 3 , A. Casanova 3 , E. Clavijo 4 , J. Solera 5, A.
Orduña 6 and I. Dorronsoro 7 . (1) Departamento de Microbiología, Universidad de Navarra. Pamplona,
Spain. (2) KIT Biomedical Research. Royal Tropiocal Institute. Amsterdam. The Netherlands. (3)
Hospital de Bellvitge, Barcelona, Spain. (4) Hospital Virgen de la Victoria. Málaga. Spain. (5)
Departamento de Medicina Interna. Facultad de Medicina. (6) Departamento de Microbiología.
Universidad de Valladolid. Valladolid. Spain. (7) Hospital de Navarra. Pamplona. Spain.
Although occurrence of Rheumatoid Factors (RF) have often been linked to
cases of rheumatic arthritis, some chronic bacterial infection also result in an
induction of RF. In these instances, RF is frequently found to be of the IgM isotype.
Although several authors have reported the presence of RF in patients with
brucellosis, the potential interference of RF in diagnostic tests based on the detection
of IgM antibodies (Ab’s) to Brucella, has not been evaluated. During the testing of a
rapid flow immunochromatographic system (LF-IgM) for the detection of IgM Ab’s in
patients with brucellosis, we obtained a false positive result due to interference by
RF. To further evaluate the potential relevance of this finding, we first screened sera
(n=450) from brucellosis patients for RF using latex particles coated with human
gammaglobulin. We then subjected the RF-positive samples (n=9) to serological
assays for the diagnosis of human brucellosis including ELISA-IgM, LF-IgM and
seroaglutinatión (SAT). All these tests were performed both subsequently and prior to
absorption of the RF-positive sera with anti-RF Ab. Finally, the presence of other
relevant Ab types (dithiothreitol-sensitive Ab’s; non-agglutinating IgG Ab’s, Native-
Haptene-reactive Ab’s and anti-cytosolic-proteins Ab’s) was also investigated in the
RF-positive samples.
Prior to their absorption with anti-RF-Ab, all 9 RF-positive sera gave also
positive result as determined by ELISA-IgM, LF-IgM and LF-IgG. However, in five
cases absorption with anti-RF Ab totally abolished reactivity detectable by ELISA-
IgM, LF-IgM and SAT (the latter with the exception of a serum containing high titer of
agglutinating IgA). Interestingly, these sera corresponded to patients with relapse
(n=3) and patients with long-lasting brucellosis (n=2). Consistent with these findings,
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Brucellosis 2003 International Research Conference