Table 1.

Outcomes of the diagnostic algorithm for acute Q fever in an outbreak setting and definitions

Outcome in the diagnostic algorithmDefinition
Acute Q feverPresence of IgM and IgG antibodies to phase II antigens with or without IgM and IgG antibodies to phase I antigens or PCR positivity
Past resolved Q feverPresence of IgG antibodies to phase II antigens with or without IgG antibodies to phase I antigens in the absence of IgM antibodies
No acute Q feverAbsence of a serologic response in serum samples obtained >14 days after onset of disease
Cross-reactivityPresence of false-positive IgM antibodies to phase II antigens detected by ELISA but not confirmed by additional tests in first or follow-up serum samples
Inconclusive outcomeNoncompliance with the request to refer a follow-up serum sample
Inconsistency with the diagnostic algorithmNonadherence to the flowchart of the diagnostic algorithm