Abstract
BackgroundBrucellosis is an infectious-allergic zoonotic disease caused by bacteria of the genus Brucella. Early diagnosis is the key to preventing, treating, and controlling brucellosis. Fluorescence polarization immunoassay (FPA) is a new immunoassay for relatively rapid and accurate detection of antibodies or antigens based on antigen–antibody interaction. However, there is no report on FPA-based detection of human brucellosis in China. Therefore, this study is to evaluate the value of FPA for the diagnosis of human brucellosis in China.MethodsWe recruited 320 suspected brucellosis cases who had the clinical symptoms and epidemiological risk factors between January and December, 2019. According to China Guideline for Human Brucellosis Diagnosis, the Rose Bengal test (RBT) was used for the screening test, and the serum agglutination test (SAT) was used as the confirmatory test. Brucellosis was confirmed only if the results of both tests were positive. Additionally, FPA and enzyme linked immune sorbent assay (ELISA) were compared with SAT, and their sensitivity, specificity, coincidence rate and consistency coefficient (Kappa value) as diagnostic tests were analyzed individually and in combination. The optimal cut-off value of FPA was also determined using the receiver operator characteristic (ROC) curve.ResultsThe optimum cut-off value of FPA was determined to be 88.5 millipolarization (mP) units, with a sensitivity of 94.5% and specificity of 100.0%. Additionally, the coincidence rate with the SAT test was 96.6%, and the Kappa value (0.9) showed excellent consistency. The sensitivity and specificity of FPA and ELISA combined were higher at 98.0% and 100.0% respectively.ConclusionsWhen the cut-off value of FPA test is set at 88.5 mP, it has high value for the diagnosis of brucellosis. Additionally, when FPA and ELISA are combined, the sensitivity of diagnosis is significantly improved. Thus, FPA may have potential in the future as a diagnostic method for human brucellosis in China.Graphic abstract
Highlights
Brucellosis is an infectious-allergic zoonotic disease caused by bacteria of the genus Brucella
In Fluorescence polarization immunoassay (FPA), the titer of antibody bound to the antigen directly is determined with the help of a fluorescent dye attached to a small antigen fragment, which is excited by plane polarized light of a specific wavelength
Optimal cut‐off value for FPA At present, the FPA test is not included in the diagnostic criteria for brucellosis in China
Summary
Brucellosis is an infectious-allergic zoonotic disease caused by bacteria of the genus Brucella. There is no report on FPA-based detection of human brucellosis in China. This study is to evaluate the value of FPA for the diagnosis of human brucellosis in China. Brucellosis is an infectious-allergic zoonotic disease caused by bacteria of the genus Brucella [1]. More than 170 countries have reported human cases of brucellosis, and approximately 500 000 new cases are reported each. Brucellosis is a highly neglected zoonotic disease, according to the World Health Organization [4]. In China, brucellosis has been recognized as an epidemic on account of its high incidence and wide spread since the mid-1990s, and it is an important public health problem in the country [6]
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