Table 1. Dutch consensus guideline on chronic Q fever diagnostics*.

Proven chronic Q fever	Probable chronic Q fever	Possible chronic Q fever
1. Positive Coxiella burnetii PCR of blood or tissue†	IFA ≥1:1,024 for C. burnetii phase I IgG‡	IFA ≥ 1:1,024 for C. burnetii phase I IgG‡ without manifestations meeting the criteria for proven or probable chronic Q fever
OR	AND any of the following:
2. IFA ≥1:800 or 1:1,024 for C. burnetii phase I IgG†	Valvulopathy not meeting the major criteria of the modified Duke criteria (13)
AND	Known aneurysm and/or vascular or cardiac valve prosthesis without signs of infection by means of TEE/ TTE, FDG-PET, CT, MRI, or AUS
Definite endocarditis according to the modified Duke criteria (13)
OR
Proven large vessel or prosthetic infection by imaging studies (FDG-PET, CT, MRI, or AUS)	Suspected osteomyelitis or hepatitis as manifestation of chronic Q fever
	Pregnancy
	Symptoms and signs of chronic infection, such as fever, weight loss and night sweats, hepato-splenomegaly, persistent raised ESR and CRP
	Granulomatous tissue inflammation, proven by histological examination
	Immunocompromised state

*Source (14). IFA, immunofluorescence assay; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography; FDG-PET, fluorodeoxyglucose positron emission tomography; CT, computed tomography; MRI, magnetic resonance imaging; AUS, abdominal ultrasound; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein.
†In the absence of acute infection.
‡Cut-off depends on the IFA technique used, whether in-house developed or commercial.