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Journal of Clinical Microbiology, November 2000, p. 4000-4005, Vol. 38, No. 11
Departamento de Microbiología,
Facultad de Medicina,1 Unidad de
Investigación, Hospital Universitario,2
and Laboratorio Regional de Brucelosis, Servicio Territorial de
Salud Pública,3 Valladolid, Spain
Received 11 February 2000/Returned for modification 1 June
2000/Accepted 27 August 2000
We evaluated the validity and the usefulness of a new test for the
diagnosis of human brucellosis based on an immunocapture-agglutination technique. A total of 315 sera from 82 patients with a diagnosis of
brucellosis, 157 sera from patients in whom brucellosis was suspected
but not confirmed, and 412 sera from people living in rural areas with
endemic brucellosis were studied. The seroagglutination test (SAT),
Coombs anti-Brucella test, and Brucellacapt test were evaluated. All
the initial sera from the 82 patients proved to be positive in
Brucellacapt and Coombs tests, while only 75 (91.4%) were positive in
the SAT. If a
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Evaluation of an Immunocapture-Agglutination Test (Brucellacapt)
for Serodiagnosis of Human Brucellosis
1/160 diagnostic threshold titer was defined for the
Brucellacapt test, Coombs test, and SAT, the sensitivities were 95.1, 91.5, and 65.8%, respectively. Taking the same diagnostic threshold
titer for the 157 sera from the unconfirmed but suspected patients, the
specificities of the Brucellacapt, Coombs, and SAT were 81.5, 96.2, and
100%, respectively; for the 412 control sera, the specificities were
99.0, 99.8, and 100%. The diagnostic efficiency (area below the
receiver operating characteristic curve) of Brucellacapt was 0.987852 (95% confidence interval [CI], 0.95109 to 0.99286), very similar to
the diagnostic efficiency of the Coombs test (0.97611; 95% CI, 0.94781 to 0.99146) and higher than that of SAT (0.91013; 95% CI, 0.86649 to
0.94317). The results of the Brucellacapt test were compared with those
of the Coombs test (correlation coefficient, 0.956; P = 0.000) and SAT (correlation coefficient, 0.866; P = 0.000). The study shows very good correlation between the Brucellacapt
and Coombs tests, with a high concordance between titers obtained in
the two tests. Nevertheless, lower correlation and concordance were
found between the Brucellacapt and Coombs tests when the results for
titers of
1/160 were compared (0.692; P = 0.000). In
acute brucellosis, the Brucellacapt and Coombs tests render positive
titers of
1/160. When the titers are lower, they increase
significantly in the following 30 days, despite the evolution of SAT
titers. In contrast, Brucellacapt and Coombs titers are always high
(
1/640) in brucellosis with long evolution, whether SAT titers are
higher or lower than 1/160.
*
Corresponding author. Mailing address: Dpto
Microbiología, Facultad de Medicina, Avda Ramon y Cajal s/n,
47005 Valladolid, Spain. Phone: 34 983423063. Fax: 34 983423066. E-mail: orduna{at}med.uva.es.
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