The value of ELISA vs. negative Coombs findings in the serodiagnosis of human brucellosis

Abstract

This study was conducted to assess the value of ELISA findings in relation to negative findings in the Brucella-antihuman globulin (Coombs) test and in relation to the clinical condition of patients. One hundred and thirty three serum specimens, representing the same number of patients, submitted for serologic testing for brucellosis and showing negative Coombs, were tested by ELISA to determine their Brucella-IgG, -IgM and -IgA antibodies. Concordant negative results between Coombs and ELISA were found in 95 (71.4%) patients whose medical records also did not reveal suggestive clinical signs or symptoms of brucellosis. The elevated ELISA readings in the remaining 38 (28.6%) patients were distributed as follows: IgG + IgM + IgA in 1 patient, IgG + IgM in 8 patients, IgG alone in 24 patients and IgM alone in 5 patients. The clinical review of these patients indicated no current disease in 21 (15.8%), scanty evidence of brucellosis in 8 (6.0%) and suggestive or sufficient evidence in 9 (6.8%). Thus, ELISA is the test of choice to resort to in the case of clinical suspicion of brucellosis, even when the Coombs test shows negative findings.