Evaluation of a Diagnostic Algorithm for Acute Q Fever in an Outbreak Setting

Abstract

In the peak of the 2009 Q fever outbreak in the Netherlands, we introduced a diagnostic algorithm for acute Q fever with an enzyme-linked immunosorbent assay for immunoglobulin M antibodies to Coxiella burnetii phase II antigens (MII screen) as an initial step. Subsequently, an immunofluorescence assay or PCR was performed depending on the MII screen outcome, date of onset of disease, and inpatient or outpatient setting. The impact of MII screen on the number of immunofluorescence assays performed and the contribution of PCR to diagnosis were retrospectively evaluated in 825 patients referred in a 17-day period. Acute Q fever was diagnosed in 256 patients. The introduction of MII screen reduced the number of immunofluorescence assays performed by more than 80%. In 103 patients, PCR analysis contributed to the diagnosis of acute Q fever. Q fever diagnostics were hampered by the fact that for a high number of patients the date of onset of disease was not provided and the requested follow-up serum samples were not received.

High Coxiella burnetii DNA Load in Serum during Acute Q Fever Is Associated with Progression to a Serologic Profile Indicative of Chronic Q Fever

“…Due to the enormous number of samples that were submitted to our laboratory for Q fever diagnostic tests (over 18,000 samples in 2009), IFA results sometimes were not titrated but were recorded only as "positive." In addition, IgG phase I and II levels were not always determined in samples submitted for qPCR testing with a suspicion of acute Q fever (when ELISA/IFA IgM phase II results were negative [25]). Therefore, to establish seroconversion rates, we assumed that the IgM phase II-negative qPCR samples were also negative for IgG phase I and II.…”

“…IFAs for IgM and IgG phase I and phase II (Focus Diagnostics, Inc., Cypress, CA) were performed on all MII screen-positive and borderline-positive serum samples, according to the manufacturer's instructions. Titers of 1:32 or greater were considered positive (25). After a patient was diagnosed with acute Q fever, follow-up samples were requested at 3, 6, and 12 months, to monitor the development of chronic Q fever (27).…”

“…When the date of disease onset was missing from requests from GPs, qPCR was not performed and a second sample was requested. In cases in which qPCR was performed and the result was negative, a second sample (after 14 days) also was requested (25). IFAs for IgM and IgG phase I and phase II (Focus Diagnostics, Inc., Cypress, CA) were performed on all MII screen-positive and borderline-positive serum samples, according to the manufacturer's instructions.…”

“…Diagnostic evaluations for patients suspected of having acute Q fever were performed according to the diagnostic algorithm that was established in our laboratory in 2009 (25). In brief, all serum samples were initially screened with a qualitative ELISA for IgM phase II (MII screen), according to the manufacturer's instructions (Institut Virion/Serion GmbH, Würzburg, Germany), with a DSX automated ELISA processing system (Dynex Technologies, Chantilly, VA).…”

“…In order to improve laboratory logistics during the outbreak situation, an algorithm was developed to cope with the large number of submitted samples. IgM phase II tests, enzyme-linked immunosorbent assays (ELISAs), and PCR assays were included as routine procedures within this algorithm (see Materials and Methods for more details) (25).…”