Localizing chronic Q fever: a challenging query

D. Barten, C. Delsing, S. Keijmel, T. Sprong, J. Timmermans, W. Oyen, M. Nabuurs-Franssen and C. Bleeker-Rovers

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.



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.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.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.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.