Utility of positron emission tomography imaging in the diagnosis of chronic Q fever: A Systematic Review

Abstract

Chronic Q fever is a diagnostic challenge. Diagnosis relies on serology and/or the detection of DNA from blood or tissue samples. PET-CT identifies tissues with increased glucose metabolism, thus identifying foci of inflammation. Our aim was to review the existing literature on the use of PET-CT to help diagnose chronic Q fever. A literature search was conducted in PubMed and Google Scholar to ascertain publications that included the terms 'Positron Emission Tomography' and 'PET CT' in combination with subheadings 'chronic Q fever' and 'Coxiella burnetii' within the search. To broaden our search retrieval, we used the terms 'chronic Q fever' and 'PET-CT'. Published literature up to 16 th April 2020 was included. 274 articles were initially identified. Post-exclusion criteria, 46 articles were included. Amongst case reports and series, the most frequent focus of infection was vascular, followed by musculoskeletal then cardiac. 79.5% of patients had a focus detected with 55.3% of these having proven infected prosthetic devices. Amongst the retrospective and prospective studies, a total of 394 positive sites of foci were identified with 186 negative cases. Some had follow-up scans (53), with 75.5% showing improvement or resolution. Average timeframe for documented radiological resolution postinitiating treatment was 8.86 months. PET-CT is a useful tool in the management of chronic Q fever. Knowledge of a precise focus enables for directed surgical management helping reduce microbial burden, preventing future complications. Radiological resolution of infection can give clinicians reassurance on whether antimicrobial therapy can be ceased earlier, potentially limiting side effects.

Case report: a missed case of chronic Q fever infective endocarditis demonstrating the ongoing diagnostic challenges

“…Coxiella burnetti,a small intracellular Gram-negative bacterium, is the aetiologic agent of Q fever; a worldwidezoonotic disease with a broad clinical spectrum ranging from either asymptomatic or mild disease to life threateninginfection (1,2). Animals, in particular small ruminants, act as reservoirs for the bacterium with transmission occurring through close contact with contaminated tissue in particular birth products of these animals (1,3). Ticks are also important vectors of transmission (4).…”

“…Acute Q fever can present with flu-like symptoms, pneumonia or hepatitis, or be asymptomatic [3]. Approximately 1–5 % of acutely infected humans will go on to develop chronic Q fever, which can manifest years after primary infection [7].…”

“…Approximately 1–5 % of acutely infected humans will go on to develop chronic Q fever, which can manifest years after primary infection [7]. Early chronic Q fever can present with constitutional symptoms, including fevers, night sweats and weight loss, but more severe sequelae, including infective endocarditis and vascular infection, are associated with chronic Q fever, with arthritis and osteomyelitis also described in the literature [3, 7].…”

“…Airborne transmission is prominent and the organism is highly infectious; even distant contact with infected animals can lead to infection [5]. Australia has an age-standardized Q fever seroprevalence of 5.6 % and it is most commonly found in Queensland and New South Wales [3, 6].…”