Table 1 Criteria for diagnosis of chronic Q fever, according to the Dutch Q fever consensus group [3]

Proven

• Positive C. burnetii in tissue or blood in absence of acute Q fever infection OR

• IFA phase I IgG titer ≥1:1,024 with definite endocarditis according to the revised Duke criteria* OR

• IFA phase I IgG titer ≥1:1,024 with vascular infection diagnosed with PET/CT, CT, MRI or ultrasound testing

Probable

IFA phase I IgG titer ≥1:1,024 with one of the following manifestations:

• Valvular deviation that does not meet the definition of endocarditis according to the Duke criteria

• Aneurysm, valvular- or vascular prosthesis without an infection on PET/CT, CT, MRI or ultrasound testing

• Suspicion of osteomyelitis or hepatitis as an expression of chronic Q fever

• Pregnancy

• Clinical symptoms of chronic infection (e.g. fever, weight loss, night sweating)

• Granulomatous infection

• Immunodeficiency

Possible

Solely a phase I IgG ≥1:1,024^¥, without any of the manifestations mentioned in the categories proven and probable.