Q Fever: An Old but Still a Poorly Understood Disease

Table 1

Cutoff proposal for Q fever diagnosis by using microimmunofluorescence and interpretation of serological results obtained with a single serum sample.

Phase II antibody titer		Phase I antibody titer (IgG)	Interpretation
IgG	IgM
≤100			Active Q fever improbable
≥200	≥50		Acute Q fever (100% predictive)
		≥1 : 800	Chronic Q fever (98% predictive)
		≥1 : 1,600	Chronic Q fever (100% predictive)