Abstract
Q fever is a zoonosis caused by Coxiella burnetii, a Gram-negative pathogen with a complex life cycle and a high impact on public and animal health all over the world. The symptoms are indistinguishable from those belonging to other diseases, and the disease could be symptomless. For these reasons, reliable laboratory tests are essential for an accurate diagnosis. The aim of this study was to validate a novel enzyme-linked immunosorbent assay (ELISA) test, named the Chorus Q Fever Phase II IgG and IgM Kit (DIESSE, Diagnostica Senese S.p.A), which is performed by an instrument named Chorus, a new device in medical diagnostics. This diagnostic test is employed for the detection of antibodies against C. burnetii Phase II antigens in acute disease. Our validation protocol was performed according to the Italian Accreditation Body (ACCREDIA) (Regulation UNI CEI EN ISO/IEC 17025:2018 and 17043:2010), OIE (World Organization for Animal Health), and Statement for Reporting Studies of Diagnostic Accuracy (STARD). Operator performance was evaluated along with the analytical specificity and sensitivity (ASp and ASe) and diagnostic accuracy of the kit, with parameters such as diagnostic specificity and sensitivity (DSp and DSe) and positive and negative predictive values (PPV and NPV), in addition to the repeatability. According to the evaluated parameters, the diagnostic ELISA test was shown to be suitable for validation and commercialization as a screening method in human sera and a valid support for clinical diagnostics.
Highlights
Q fever is a disease caused by Coxiella burnetii, a ubiquitous, zoonotic, Gram-negative bacterium isolated from a wide variety of animals, arthropods, and environmental samples, with a worldwide distribution, except for New Zealand [1]
We evaluate the analytical and diagnostic performances of a novel device in medical diagnostics, the Chorus Q Fever Phase II IgG and IgM Kit (DIESSE, Diagnostica Senese S.p.A), to verify if this method is suitable for validation
The results concerning the evaluation of all parameters evidenced excellent values and demonstrated that the novel Chorus Q fever enzyme-linked immunosorbent assay (ELISA) is a robust assay for detecting C. burnetii antibodies during the acute phase of the disease
Summary
Q fever is a disease caused by Coxiella burnetii, a ubiquitous, zoonotic, Gram-negative bacterium isolated from a wide variety of animals, arthropods, and environmental samples, with a worldwide distribution, except for New Zealand [1]. The axenic cultivation of C. burnetii has led to this pathogen no longer being considered an obligate intracellular bacterium [2,3]. C. burnetii exists in two distinct morphological variants, a small-cell variant (SCV) and a large-cell variant (LCV), corresponding, respectively, to the metabolically inactive and replicative forms of. C. burnetii in the environment and in the cell hosts, respectively [4]. C. burnetii can be found in two phases, called Phase I and Phase II, that are linked to the antigenic variations of its lipopolysaccharide (LPS). Phase I represents the natural phase, which is highly infectious with a smooth LPS, while Phase II is obtained in vitro after C. burnetii propagation in cell culture; it is non-infective, with a rough-truncated. Mainly goats, sheep, and cattle, represent the most important reservoir of infection of this bacterium [6]. Wild vertebrates are considered as putative reservoirs of
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