title: Localizing chronic Q fever: a challenging query.
abstract: BACKGROUND
  Chronic Q fever usually presents as endocarditis or endovascular infection. We investigated whether 18F-FDG PET/CT and echocardiography were able to detect the localization of infection. Also, the utility of the modified Duke criteria was assessed.
  
  
  METHODS
  Fifty-two patients, who had an IgG titre of  ≥ 1024 against C. burnetii phase I ≥ 3 months after primary infection or a positive PCR ≥ 1 month after primary infection, were retrospectively included. Data on serology, the results of all imaging studies, possible risk factors for developing proven chronic Q fever and clinical outcome were recorded.
  
  
  RESULTS
  According to the Dutch consensus on Q fever diagnostics, 18 patients had proven chronic Q fever, 14 probable chronic Q fever, and 20 possible chronic Q fever. Of the patients with proven chronic Q fever, 22% were diagnosed with endocarditis, 17% with an infected vascular prosthesis, and 39% with a mycotic aneurysm. 56% of patients with proven chronic Q fever did not recall an episode of acute Q fever. Ten out of 13 18F-FDG PET/CT-scans in patients with proven chronic Q fever localized the infection. TTE and TEE were helpful in only 6% and 50% of patients, respectively.
  
  
  CONCLUSIONS
  If chronic Q fever is diagnosed, 18F-FDG PET/CT is a helpful imaging technique for localization of vascular infections due to chronic Q fever. Patients with proven chronic Q fever were diagnosed significantly more often with mycotic aneurysms than in previous case series. Definite endocarditis due to chronic Q fever was less frequently diagnosed in the current study. Chronic Q fever often occurs in patients without a known episode of acute Q fever, so clinical suspicion should remain high, especially in endemic regions.
authors.affiliation: Radboud Expertise Centre for Q fever, Department of Internal Medicine, Division of Infectious Diseases, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands. C.Bleeker-Rovers@AIG.umcn.nl.
authors.forename: Dennis G
authors.initials: DG
authors.lastname: Barten
authors.forename: Corine E
authors.initials: CE
authors.lastname: Delsing
authors.forename: Stephan P
authors.initials: SP
authors.lastname: Keijmel
authors.forename: Tom
authors.initials: T
authors.lastname: Sprong
authors.forename: Janneke
authors.initials: J
authors.lastname: Timmermans
authors.forename: Wim J G
authors.initials: WJ
authors.lastname: Oyen
authors.forename: Marrigje H
authors.initials: MH
authors.lastname: Nabuurs-Franssen
authors.forename: Chantal P
authors.initials: CP
authors.lastname: Bleeker-Rovers
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000276:immunology; D016997:Coxiella burnetii / Q000276:immunology / Q000302:isolation & purification; D004452:Echocardiography; D004696:Endocarditis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000276:immunology / Q000382:microbiology; D004697:Endocarditis, Bacterial; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011778:Q Fever / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000276:immunology / Q000382:microbiology; D012189:Retrospective Studies
chemical_list: D000907:Antibodies, Bacterial