Serology in chronic Q fever is still surrounded by question marks.

Detection of antibodies using immunofluoresence tests (IFAT) is recommended for diagnosis of chronic Q fever, but other commercial antibody assays are also available. We compared an enzyme-linked immunosorbent assay (ELISA) (Virion/Serion) and a complement fixation test (CFT) (Virion/Serion) for the detection of Coxiella burnetii IgG phase I and IgA phase I in early- and follow-up serum samples from patients with chronic Q fever, diagnosed according to an algorithm that involves IFAT. For this, we tested sera of 49 patients, including 30 proven, 14 probable and five possible chronic Q fever cases. Sensitivity of CFT for diagnosis of chronic Q fever was suboptimal (85 %), as eight patients, including five with chronic Q fever, tested negative at time of diagnosis, whereas IgG phase I antibodies were detected in these five patients by ELISA. Sensitivity of ELISA was higher, although three probable patients were missed. No differences in ELISA IgA phase I detection between proven chronic Q fever and probable were observed; instead possible patients were in majority IgA negative (60 %). Serological examination using ELISA and CFT in follow-up sera from 26 patients on treatment was unsatisfactory. Like IFAT, all kinetic options were possible: decreasing, remaining stable or even increase during time. This study demonstrated that the sensitivity of CFT-based phase I antibody detection is low and therefore not recommended for diagnosis of chronic Q fever. Based on our results, serological follow-up to guide treatment decisions was of limited value.

A combination of interferon-gamma and interleukin-2 production by Coxiella burnetii-stimulated circulating cells discriminates between chronic Q fever and past Q fever.

Infection with Coxiella burnetii may lead to life-threatening chronic Q fever endocarditis or vascular infections, which are often difficult to diagnose. The present study aims to investigate whether measurement of in-vitro interferon-gamma (IFN-γ) production, a key cytokine in the immune response against C. burnetii, differentiates chronic from a past cleared infection, and whether measurement of other cytokines would improve the discriminative power. First, C. burnetii-specific IFN-γ production was measured in whole blood of 28 definite chronic Q fever patients and compared with 135 individuals with past Q fever (seropositive controls) and 908 seronegative controls. IFN-γ production was significantly higher in chronic Q fever patients than in controls, but with overlapping values between patients and seropositives. Secondly, the production of a series of other cytokines was measured in a subset of patients and controls, which showed that interleukin (IL)-2 production was significantly lower in patients than in seropositive controls. Subsequently, measuring IL-2 in all patients and all controls with substantial IFN-γ production showed that an IFN-γ/IL-2 ratio >11 had a sensitivity and specificity of 79% and 96%, respectively, to diagnose chronic Q fever. This indicates that a high IFN-γ/IL-2 ratio is highly suggestive for chronic Q fever. In an additional group of 25 individuals with persistent high anti-Coxiella phase I IgG titres without definite chronic infection, all but six showed an IFN-γ/IL-2 ratio <11. In conclusion, these findings hold promise for the often difficult diagnostic work-up of Q fever and the IFN-γ/IL-2 ratio may be used as an additional diagnostic marker.

Targeted screening as a tool for the early detection of chronic Q fever patients after a large outbreak.

In the aftermath of the Dutch Q fever outbreak, an increasing number of patients are being diagnosed with chronic Q fever. Most of these patients are unaware of being infected with Coxiella burnetii, the causative agent of Q fever. To find patients in an earlier, asymptomatic stage, a targeted screening strategy (TSS) for patients with risk factors for chronic Q fever was started in the southeast region of Noord-Brabant. In total, 763 patients were tested using an IgG phase II indirect fluorescent antibody test (IFAT), of which 52 (7 %) patients tested positive. Ten of these 52 patients displayed a chronic Q fever serological profile. All of these 10 patients had a heart valve(s) or (endo-)vascular prosthesis. All except one were asymptomatic. Suggestive signs for chronic infections on positron emission tomography-computed tomography (PET-CT) were demonstrated in 5 (50 %) of these patients. Forty-two out of the 52 patients with a positive screening test showed a past Q fever serological profile. After a year of follow-up (every 3 months), none of these patients showed elevation of antibody titres and no new chronic Q fever patients were found in this group. A targeted screening programme is a useful instrument for detecting patients at risk of developing chronic Q fever.

Detection of phase I IgG antibodies to Coxiella burnetii with EIA as a screening test for blood donations.

The presence of a high phase I IgG antibody titre may indicate chronic infection and a risk for the transmission of Coxiella burnetii through blood transfusion. The outbreak of Q fever in the Netherlands allowed for the comparison of an enzyme immunoassay (EIA) with the reference immunofluorescence assay (IFA) in a large group of individuals one year after acute Q fever. EIA is 100 % sensitive in detecting high (≥1:1,024) phase I IgG antibody titres. The cost of screening with EIA and confirming all EIA-positive results with IFA is much lower than screening all donations with IFA. This should be taken into account in cost-effectiveness analyses of screening programmes.

Evaluation of commonly used serological tests for detection of Coxiella burnetii antibodies in well-defined acute and follow-up sera.

In this study, we compared Coxiella burnetii IgG phase I, IgG phase II, and IgM phase II detection among a commercially available enzyme-linked immunosorbent assay (ELISA) (Virion/Serion), an indirect fluorescent antibody test (IFAT) (Focus Diagnostics), and a complement fixation test (CFT) (Virion/Serion). For this, we used a unique collection of acute- and convalescent-phase sera from 126 patients with acute Q fever diagnosed by positive Coxiella burnetii PCR of blood. We were able to establish a reliable date of onset of disease, since DNA is detectable within 2 weeks after the start of symptoms. In acute samples, at t = 0, IFAT demonstrated IgM phase II antibodies in significantly more sera than did ELISA (31.8% versus 19.7%), although the portion of solitary IgM phase II was equal for IFAT and for ELISA (18.2% and 16.7%, respectively). Twelve months after the diagnosis of acute Q fever, 83.5% and 62.2% of the sera were still positive for IgM phase II with IFAT and ELISA, respectively. At 12 months IFAT IgG phase II showed the slowest decline. Therefore, definitive serological evidence of acute Q fever cannot be based on a single serum sample in areas of epidemicity and should involve measurement of both IgM and IgG antibodies in paired serum. Based on IgG phase II antibody detection in paired samples (at 0 and 3 months) from 62 patients, IFAT confirmed more cases than ELISA and CFT, but the differences were not statically significant (100% for IFAT, 95.2% for ELISA, and 96.8% for CFT). This study demonstrated that the three serological tests are equally effective in diagnosing acute Q fever within 3 months of start of symptoms. In follow-up sera, more IgG antibodies were detected by IFAT than by ELISA or CFT, making IFAT more suitable for prevaccination screening programs.

Chronic Q fever: review of the literature and a proposal of new diagnostic criteria.

A review was performed to determine clinical aspects and diagnostic tools for chronic Q fever. We present a Dutch guideline based on literature and clinical experience with chronic Q fever patients in The Netherlands so far. In this guideline diagnosis is categorized as proven, possible or probable chronic infection based on serology, PCR, clinical symptoms, risk factors and diagnostic imaging.

Vascular complications of Q-fever infections.

INTRODUCTION: Coxiella burnetii is a strict intracellular pathogen causing Q fever, a worldwide zoonosis with an extensive animal reservoir. Chronic Q fever infections are frequently associated with cardiovascular complications, mainly endocarditis, and also aortic aneurysms and vascular-graft infection. We present four cases of chronic Q fever infections and associated vascular complications, and review the literature to identify major symptoms and assess the prevalence, treatment and outcome in these challenging patients. MATERIALS AND METHODS: The demographic and clinical data of four patients presenting at our unit were analysed. PubMed was searched to identify articles describing patients with chronic Q-fever-associated vascular complications. RESULTS: Combining our own with the published experience, 58 cases (49 male) of chronic Q-fever-associated vascular complications were identified. The average age of the patients was 64 years (range: 30-83 years). As many as 26 patients had vascular graft infections (25 Dacron/polytetrafluoroethylene (PTFE), one homograft) and 32 had infected aneurysms. The majority of these patients presented with fever (n = 40) and/or pain (n = 43). Weight loss and fatigue were seen in 25 and 14 patients, respectively. Aneurysm rupture, aorto-enteric fistulae and lower-limb embolisation were seen in nine, four and four patients, respectively. Concurrent endocarditis was seen in two patients, whereas, for 15 cases, this information was not available. Patients were treated with antibiotics for an average of 23 months (range 1-54 months). Treatment of infected vascular segments was described in 50 patients. Ten patients were treated conservatively whilst 40 underwent resection of the infected vessel and reconstruction with a graft. Major surgical complications (graft infection, n = 3;aorto-enteric fistula, n = 2; bleeding, n = 1; anastomotic leakage, n = 1; aortic dissection, n = 1; vertebral osteomyelitis, n = 3; graft thrombosis, n = 1; renal failure, n = 2; and pneumonia, n = 1) were reported in 11 cases (21%) and were not specified in 13. The overall mortality was 24% (14/58). Seven (18%) surgically treated patients died. Six of them died within 6 months of surgery and one patient at 3 years' follow-up. Seven out of 10 of the conservatively treated patients died within 3 years of diagnosis. CONCLUSION: Aneurysms associated with Q-fever infections tend to be complicated, requiring challenging surgical corrections, and long-term antibiotic treatment. Major complications and mortality rates are significant, especially in conservatively treated patients.

Acute Q fever related in-hospital mortality in the Netherlands.

INTRODUCTION: A large outbreak of acute Q fever has been reported in the Netherlands with over 3500 cases from 2007 to 2009, during which 749 patients were hospitalised. In foreign cohorts, reported mortality rates in patients hospitalised with acute Q fever, ranged from 0.9 to 2.4%. We analysed mortality among hospitalised patients with acute Q fever in the Netherlands. METHODS: Physicians from hospitals in the afflicted region were asked to provide details about patients who died with a diagnosis of acute Q fever between 2007 and 2009. RESULTS: Nine patients (seven males, median age 72 years) from six hospitals were reported, who died within approximately one month following hospitalisation for acute Q fever. Six definite acute Q fever cases and three probable cases were identified. Six patients presented with infiltrates on the chest X-ray and a median CURB-65 score of 3. Median time of hospitalisation was 13 days (range 1-33). All patients had serious, often coinciding, underlying conditions including chronic cardiovascular disease, chronic lung disease, diabetes mellitus and malignancy. CONCLUSION: The mortality rate of patients hospitalised because of acute Q fever was estimated at approximately 1%. Patients who died with acute Q fever were often male, of older age, and had chronic coinciding underlying conditions, which gives an a priori higher risk of death.