Low incidence and the prevalence of brucellosis among patients with pyrexia of unknown origin based on real-time polymerase chain reaction, enzyme-linked immunosorbent assay and standard agglutination test results in Puducherry, South India

Abstract

CONTEXT: Brucellosis is a zoonotic disease and an important differential to be considered in patients with pyrexia of unknown origin (PUO). The laboratory diagnosis of brucellosis has always been affected by various factors such as the slow growth of the organism and cross-reacting antibodies. Hence, a diagnostic test with high sensitivity and specificity is the key for the accurate and rapid diagnosis. AIM: The study aimed to evaluate the role of real-time polymerase chain reaction (PCR) in the rapid diagnosis of human brucellosis from direct serum samples of patients with PUO. MATERIALS AND METHODS: An observational study was conducted from October 2014 to September 2016 at a tertiary care hospital in Puducherry where 138 blood samples were obtained from the patients with PUO. Serum separated from each sample was tested for brucellosis using Cobas 480 Z real-time PCR system. Simultaneously, the samples were also subject to blood culture, standard agglutination test (SAT) and enzyme-linked immunosorbent assay (ELISA) (IgG and IgM) for brucellosis. RESULTS: All the samples were found to be negative for brucellosis using real-time PCR. Blood culture also did not yield any growth of Brucella spp. Among the serological tests, all the samples were negative by SAT, whereas two were positive for IgM and four for IgG anti-Brucella antibodies using ELISA. CONCLUSION: Brucellosis is not a common cause of PUO among patients attending this hospital since all the samples were negative by highly sensitive and specific tests such as real-time PCR and blood culture. This study highlights the limitations of serological tests such as ELISA in the accurate diagnosis of brucellosis.