ELISA is superior to bacterial culture and agglutination test in the diagnosis of brucellosis in an endemic area in China

Background: Brucellosis is endemic in many areas in China. The current diagnosis of Brucellosis predominantly relies on the traditional bacterial culture and serum agglutination test. In this study, we aimed to explore the value of ELISA in the diagnosis of Brucellosis in Chinese population. Methods: We recruited 235 patients with a diagnosis of Brucellosis at different clinical stages: 117 in acute, 78 in subacute, and 40 in chronic. We also recruited 248 control patients who presented with similar clinical symptoms but with a different diagnosis other than Brucellosis. In addition, 90 healthy volunteers were also recruited. Bacterial culture, agglutination test and ELISA assay were performed to detect Brucella spp. Results: Among 235 patients with Brucellosis, 51 (21.7%) was positive for bacterial culture, 150 (63.8%) were positive by agglutination test, and 232 (98.7%) were positive by ELISA (IgG and/or IgM). When we stratified the patients based on the disease stages (acute, subacute and chronic), ELISA was the most sensitive method and showed a highest positive rate in all stages. By Receiver Operating Characteristic Curve analysis of ELISA results, we found that measurement of IgG level was superior to measurement of IgM level (AUC, 0.993 versus 0.877). Since the measurement of IgG itself missed rare cases in acute phase, we recommended measuring IgG and IgM simultaneously by ELISA for the diagnosis of Brucellosis. In term of the specificity of ELISA in the diagnosis of Brucellosis, our study showed that only 1.6% (4/248) non-Brucellosis patients were positive by ELISA; all positive cases were IgM only and none showed positive IgG. Similar results were found in healthy volunteers. In summary, our study concluded that ELISA is the most sensitive and specific method to detect Brucellosis in Chinese population. Conclusions: ELISA assay is sensitive, fast, and convenient to detect Brucellosis. It shows the high sensitivity and specifity and should be used as a routine lab test when Brucellosis is suspected in clinical practice.