Evaluation of different serological techniques in laboratory diagnosis of brucellosis

Diagnosis of brucellosis is vital for early institution of proper therapy as untreated cases may progress to chronic stage. Though the demonstration of the causative agent in blood is considered as the most conclusive test in the diagnosis of brucellosis, isolation of brucella organism by blood culture is relatively low. Hence a number of sensitive and rapid serological tests have been introduced for the diagnosis of brucellosis. In the present study, an attempt was made to compare the efficacies of existing serological tests such as agglutination reaction with newer rapid tests which help in the detection of either specific antigen or antibody. The study included specimens from 80 patients clinically suspected to be suffering from brucellosis and 20 apparently healthy controls. All serum samples were subjected for evidence of brucellosis by five serological tests viz, standard tube agglutination test, 2-mercaptoethanol test, modified antiglobulin test, counter immuno-electrophoresis and passive haemagglutination test for antibody detection and two serological tests viz, counter immunoelectrophoresis and latex agglutination test for antigen detection. Eighty blood samples were processed for microbiological evidence of brucellosis and yielded only 8 isolates of Brucella melitensis of biotype 1. By standard tube agglutination test, 25 sera showed titre of brucella agglutinins equal to more than the diagnostic titre (i.e., more than or equal to 160 IU). Counter immuno-electrophoresis test and latex agglutination showed presence of antigen in 3 and 4 blood culture negative cases respectively.