title: [The value of the immunoglobulin G avidity test for the serologic diagnosis of brucellosis].
abstract: In order to investigate the value of immunoglobulin G (IgG) avidity test for the serological diagnosis of Brucella infections, a total of 118 patients (74 male, 44 female; mean age: 43 +/- 18.7 years) were included into the present study. The patients have been diagnosed with the characteristic clinical findings, > or = 1/160 antibody titers in standard tube agglutination (STA) test and/or blood culture positivities. Brucella spp. have been grown in blood cultures of 78 patients, and STA test results were found positive (> or = 1/160 titers) in 117 patients. The diagnosis of a patient with 1/80 STA titer was based on the blood culture positivity. By enzyme immunoassay (ELISA), 3 patients (2.5%) were found positive for IgM, 14 (11.9%) were positive for IgG, and 101 (85.6%) were positive for both IgM and IgG. The patients who were found IgG positive have been grouped according to their duration of complaints. Group 1 included 99 patients with the history of brucellosis < or = 6 months, and group 2 included 16 patients with the history of brucellosis > 6 months. IgG avidity test was performed by ELISA in 115 IgG positive serum samples, with the denaturation substance (8 M urea). The cut-off value for IgG avidity index (AI) was accepted as 40%, and the avidity maturation period was defined as 6 months. As a result, the rates of patients who had low IgG AI in group 1 and 2 were found as 91.9% and 43.7%, respectively, while these rates were 8.1% and 56.3% for the presence of high IgG AI, respectively. The rate of low AI in group 1 was an expected result, while the rate was more than expected in group 2, indicating that Brucella antibodies with low avidity indices would not be helpful for the diagnosis of a recent infection, while Brucella antibodies with high avidity indices would be useful for the elimination of a recent infection.
authors.affiliation: Ankara Numune Eğitim ve Araştirma Hastanesi, Birinci Infeksiyon Hastaliklari ve Klinik Mikrobiyoloji Kliniği, Ankara.
authors.forename: Selda Sayin
authors.initials: SS
authors.lastname: Kutlu
authors.forename: Aysel
authors.initials: A
authors.lastname: Celikbaş
authors.forename: Onder
authors.initials: O
authors.lastname: Ergönül
authors.forename: Murat
authors.initials: M
authors.lastname: Kutlu
authors.forename: Sebahat
authors.initials: S
authors.lastname: Aksaray
authors.forename: Engin
authors.initials: E
authors.lastname: Güvener
authors.forename: Başak
authors.initials: B
authors.lastname: Dokuzoğuz
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000372:Agglutination Tests; D000907:Antibodies, Bacterial / Q000097:blood*; D000915:Antibody Affinity; D016470:Bacteremia / Q000382:microbiology; D002002:Brucella / Q000276:immunology* / Q000302:isolation & purification; D002006:Brucellosis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D007075:Immunoglobulin M