Serological follow-up in patients with aorto-iliac disease and evidence of Q fever infection

The aim of this study was to provide data on the risk of developing chronic Q fever in patients with aorto-iliac disease and evidence of previous Q fever infection. Patients with an aortic and/or iliac aneurysm or aorto-iliac reconstruction (aorto-iliac disease) and evidence of previous Q fever infection were included. The presence of phase I and II Coxiella burnetii IgG antibodies was assessed periodically using immunofluorescence assay. A total of 111 patients with aorto-iliac disease were divided into three groups, based upon the serological profile [mean follow-up: 16?±?9 months (mean?±?standard deviation)]. Group 1 consisted of 30 patients with a serological trace of C. burnetii infection (negative IgG phase I, IgG phase II titer of 1:32). Of these, 36.7 % converted to serological profile matching past resolved Q fever. Group 2 included 49 patients with negative IgG phase I titer and IgG phase II titer ≥1:64. No patients developed chronic Q fever, but 14.3 % converted to a positive IgG phase I titer. Group 3 consisted of 32 patients with positive IgG phase I and positive IgG phase II titers, of which 9.4 % developed chronic Q fever (significantly different from group 2, p?=?0.039). The IgG phase I titer increased in 28.1 % of patients (from 1:64 to 1:4,096). The risk of developing chronic Q fever in patients with aorto-iliac disease and previous Q fever infection with a positive IgG phase I titer was 9.4 %. The IgG phase I titer increases or becomes positive in a substantial number of patients. A standardized serological follow-up is proposed.     

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.     

Seroprevalence of Q fever in a district located in the west Black Sea region of Turkey

Q fever is a worldwide zoonosis caused by Coxiella burnetii. In Turkey, it has been reported from the late 1940s that Q fever is endemic in humans and animals. Our objective was to evaluate the seroprevalence in Samsun Tekkeköy (north Turkey), where an outbreak of Q fever occurred in 2002. In this cross-sectional study, subjects were selected by the random proportional sampling method. All subjects were healthy with no specific symptoms and tested by the microimmunofluorescent antibody test. In total, we tested 407 subjects; 33 (8.1%) of them were identified as past evidence of infection and 22 (5.4%) were considered as evolutive form of Q fever (17 acute and five chronic forms). The seroprevalence was significantly higher among people over 30 years of age, hunters, and slaughters than the others (p?=?0.001, p?=?0.034, and p?=?0.006, respectively). We found 13.5% seropositivity among healthy subjects, confirming that Q fever is prevalent in our region and is often asymptomatic.     

Long-term serological follow-up after primary Coxiella burnetii infection in patients with vascular risk factors for chronic Q fever

We evaluated the long-term serological follow-up of patients with vascular risk factors for chronic Q fever that were previously Coxiella burnetii seropositive. C. burnetii phase I IgG titers were reevaluated in patients that gave informed consent or retrospectively collected in patients already deceased or lost to follow-up. Of 107 patients, 25 (23.4%) became seronegative, 77 (72.0%) retained a profile of past resolved Q fever infection, and five (4.7%) developed chronic Q fever. We urge clinicians to stay vigilant for chronic Q fever beyond two years after primary infection and perform serological testing based on clinical presentation.

     

Serological differentiation between acute (late control) and endocarditis Q fever.

AIMS--To differentiate the serological profiles of chronic (endocarditis) Q fever from the late follow up of acute cases. METHODS--Twenty patients (10 diagnosed with acute and 10 with endocarditis Q fever) were studied. Those diagnosed with acute infection were followed up from 2.5 to 88 months (mean 35.8 months). Serological variables included indirect immunofluorescence against phase I and II of Coxiella burnetii (IgM, IgG, and IgA), complement fixation and rheumatoid factor (RF). RESULTS--All patients with titres of IgA against phase I, after IgG removal, equal to or above 320 and a complement fixation value equal to or above 128 had endocarditis. No patient with acute Q fever had such a serological profile. CONCLUSIONS--The combination of IgA against phase I and complement fixation values may be sufficient to differentiate the serological profile of chronic (endocarditis) Q fever from the late follow up of acute cases.     

Enzyme-linked immunosorbent assay for diagnosis of chronic Q fever.

From 1982 through 1987 we diagnosed 13 chronic Q fever cases. Clinically these patients presented a culture-negative endocarditis, and all but two had high complement-fixing antibody titers to Coxiella burnetii phase I (reciprocal titer above 200). With the enzyme-linked immunosorbent assay (ELISA), titers of immunoglobulin G (IgG) to phases I and II of C. burnetii averaged 158,000 and 69,900, respectively, whereas they reached 300 and 3,200 in acute Q fever cases. Similarly, IgA to both phases of C. burnetii and IgM to phase I were consistently higher during chronic than acute Q fever. The serological follow-up of one patient with chronic Q fever over a 4-year period showed a good correlation between the titers of IgG and IgM antibody titers detected by ELISA and indirect fluorescent-antibody test (IFA) to both phases of C. burnetii. Few discrepancies appeared with IgA. Shortly after initiation of antibiotic treatment, a slow and steady decrease of the antibody titers to C. burnetii phases I and II was observed. The complement fixation, IFA, and ELISA tests showed the same type of antibody response. The ELISA proved to be an excellent diagnostic test for chronic Q fever. It distinguished negative from positive reactions clearly, and results were highly reproducible. The reading is objective, and the test is simple to perform and more sensitive than the IFA and complement fixation tests. The ELISA is recommended for serologic evaluation of patients with chronic Q fever.     

Predominant Immunoglobulin A Response to Phase II Antigen of Coxiella burnetii in Acute Q Fever

Diagnosis of acute Q fever is usually confirmed by serology, on the basis of anti-phase II antigen immunoglobulin M (IgM) titers of ≥1:50 and IgG titers of ≥1:200. Phase I antibodies, especially IgG and IgA, are predominant in chronic forms of the disease. However, between January 1982 and June 1998, we observed anti-phase II antigen IgA titers of ≥1:200 as the sole or main antibody response in 10 of 1,034 (0.96%) patients with acute Q fever for whom information was available. In order to determine whether specific epidemiological or clinical factors were associated with these serological profiles, we conducted a retrospective case-control study that included completion of a standardized questionnaire, which was given to 40 matched controls who also suffered from acute Q fever. The mean age of patients with elevated phase II IgA titers was significantly higher than that usually observed for patients with acute Q fever (P = 0.026); the patients were also more likely than controls to live in rural areas (P = 0.026) and to have increased levels of transaminase in blood (P = 0.03). Elevated IgA titers are usually associated with chronic Q fever and are directed mainly at phase I antigens. Although the significance of our findings is unexplained, we herein emphasize the fact that IgA antibodies are not specific for chronic forms of Q fever and that they may occasionally be observed in patients with acute disease. Moreover, as such antibody profiles may not be determined by most laboratories, which test only for total antibody titers to phase I and II antigens, the three isotype-specific Ig titers should be determined as the first step in diagnosing Q fever.     

Predominant immunoglobulin A response to phase II antigen of Coxiella burnetii in acute Q fever

Diagnosis of acute Q fever is usually confirmed by serology, on the basis of anti-phase II antigen immunoglobulin M (IgM) titers of >/=1:50 and IgG titers of >/=1:200. Phase I antibodies, especially IgG and IgA, are predominant in chronic forms of the disease. However, between January 1982 and June 1998, we observed anti-phase II antigen IgA titers of >/=1:200 as the sole or main antibody response in 10 of 1,034 (0.96%) patients with acute Q fever for whom information was available. In order to determine whether specific epidemiological or clinical factors were associated with these serological profiles, we conducted a retrospective case-control study that included completion of a standardized questionnaire, which was given to 40 matched controls who also suffered from acute Q fever. The mean age of patients with elevated phase II IgA titers was significantly higher than that usually observed for patients with acute Q fever (P = 0.026); the patients were also more likely than controls to live in rural areas (P = 0.026) and to have increased levels of transaminase in blood (P = 0.03). Elevated IgA titers are usually associated with chronic Q fever and are directed mainly at phase I antigens. Although the significance of our findings is unexplained, we herein emphasize the fact that IgA antibodies are not specific for chronic forms of Q fever and that they may occasionally be observed in patients with acute disease. Moreover, as such antibody profiles may not be determined by most laboratories, which test only for total antibody titers to phase I and II antigens, the three isotype-specific Ig titers should be determined as the first step in diagnosing Q fever.     

Q fever endocarditis; not always expected

Q fever endocarditis is a chronic disease with protean manifestations. The clinical and serological manifestations of nine patients diagnosed as having Q fever endocarditis during a 19-year period are reviewed. Four patients (44%) required valve replacement due to congestive heart failure. Three of these four patients were diagnosed as having Q fever endocarditis only after elective valve surgery, by histopathological examination of the valve and subsequent serological tests. Prior to surgery they were afebrile and had no other symptom or sign indicative of endocarditis. The antibiotic treatment and the decreasing titres of Q fever antibodies of all nine patients during several years of follow-up are summarized. Careful assessment of heart valves for histopathological evidence of inflammation is suggested, even after elective replacement. If found, clinical and laboratory evaluation should include determination of anti-Coxiella burnetti antibodies.     

Comparison of immunofluorescence with enzyme immunoassay for detection of Q fever

To evaluate enzyme immunoassay (EIA) as an alternative to indirect immunofluorescence assay (IFA) to screen for Q fever in humans, 157 serum samples from patients suspected of having the disease were tested for immunoglobulin G antibodies toCoxiella burnetii. The agreement between the tests and the sensitivity of EIA were excellent (96.8% and 98.4%, respectively) when an IFAtiter of > 1/160 was considered positive. All serum samples with a titer of > 1/320 in the IFA were also positive by the EIA. The EIA seems to be an acceptable alternative to IFA for screening for Q fever.     

Prevalence of chronic Q fever in patients with a history of cardiac valve surgery in an area where Coxiella burnetii is epidemic

Chronic Q fever develops in 1 to 5% of patients infected with Coxiella burnetii. The risk for chronic Q fever endocarditis has been estimated to be ≈ 39% in case of preexisting valvulopathy and is potentially even higher for valvular prostheses. Since 2007, The Netherlands has faced the largest Q fever outbreak ever reported, allowing a more precise risk estimate of chronic Q fever in high-risk groups. Patients with a history of cardiac valve surgery were selected for microbiological screening through a cardiology outpatient clinic in the area where Q fever is epidemic. Blood samples were analyzed for phase I and II IgG against C. burnetii, and if titers were above a defined cutoff level, C. burnetii PCR was performed. Chronic Q fever was considered proven if C. burnetii PCR was positive and probable if the phase I IgG titer was ≥ 1:1,024. Among 568 patients, the seroprevalence of C. burnetii antibodies (IgG titer greater than or equal to 1:32) was 20.4% (n = 116). Proven or probable chronic Q fever was identified among 7.8% of seropositive patients (n = 9). Valve characteristics did not influence the risk for chronic Q fever. Patients with chronic Q fever were significantly older than patients with past Q fever. In conclusion, screening of high-risk groups is a proper instrument for early detection of chronic Q fever cases. The estimated prevalence of chronic Q fever is 7.8% among seropositive patients with a history of cardiac valve surgery, which is substantially higher than that in nonselected populations but lower than that previously reported. Older age seems to increase vulnerability to chronic Q fever in this population.     

Study of cross-reaction between Coxiella burnetii and Legionella pneumophila using indirect immunofluorescence assay and immunoblotting.

Patients with Q fever and legionellosis may present identical clinical symptom. Differentiation of these diseases is made by serology, mainly the indirect immunofluorescence assay (IFA). Using IFA the authors tested 154 Q fever positive sera from 55 patients with acute Q fever and 28 patients with chronic Q fever for Legionella pneumophila antibodies and 57 sera from 57 patients with legionellosis for Coxiella burnetii antibodies. Of the 211 sera tested, four sera from different patients had antibodies to both C. burnetii and L. pneumophila. Using cross-adsorption studies and protein immunoblotting, no cross-reaction between C. burnetii and L. pneumophila antibodies could be identified. The moderate antibody titers against L. pneumophila in two Q fever patients and vice versa for one legionellosis patient are consistent with the incidence of seroprevalence in healthy blood donors and were not due to cross-reactivity. One patient was identified with concurrent Q fever and legionellosis.     

Q fever serology: cutoff determination for microimmunofluorescence.

Q fever, a worldwide zoonosis caused by Coxiella burnetii, lacks clinical specificity and may present as acute or chronic disease. Because of this polymorphism, serological confirmation is necessary to assess the diagnosis. Although microimmunofluorescence is our reference technique, the cutoff titers that are currently used to make a diagnosis of active or chronic Q fever were determined years ago with limited series of patients and sera. We determined the titers of immunoglobulin G (IgG), IgM, and IgA against both phases (I and II) of Coxiella burnetii. Rheumatoid factor was removed before testing IgM and IgA. We report here the various cutoff titers and the kinetics of antibody development from 2,218 first serum samples of patients, among whom 208 suffered from acute Q fever and 53 had chronic Q fever. In active Q fever, we have defined a low cutoff (phase II IgG titer < or = 100) below which the diagnosis cannot be made and would need further confirmation and confirmed a high cutoff (phase II IgG titer > or = 200 and phase II IgM titer > or = 50) over which the diagnosis can be made. For chronic Q fever diagnosis, phase I IgA titers are not contributive despite previous works claiming their usefulness; a phase I IgG titer of > or = 800 is highly predictive (98%) and sensitive (100%). We have also studied the possibility of rejecting or evoking the diagnosis of chronic Q fever by phase II IgG and IgA titers. This method is useful when phase I testing is not available, but the sensitivity remains low (57%).     

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.     

Immunological arousal during acute Q fever infection

Physicians often encounter patients who present with a vague clinical syndrome. A wide serological workup is often ordered, which may include tests for Coxiella burnetii in endemic areas. Often, the results of these tests pose new dilemma, with overlapping positive laboratory assays. The objective of this investigation was to characterise the serological overlap between acute Q fever and other infectious and immunological diseases. We retrospectively scanned the files of patients with a positive or equivocal immunoglobulin (Ig) M for C. burnetii phase II over a period of 8 years in a general hospital. Clinical and laboratory data, including antibodies to infectious agents and antibodies related to immunological states, were recorded. Anti-nuclear antibody (ANA), smooth muscle antibody (SMA) and rheumatoid factor were positive in 38%, 33.3% and 22.2% of the cases, respectively. In patients with acute Q fever, elevated IgM levels for Epstein–Barr Virus (EBV), cytomegalovirus (CMV), Mycoplasma pneumoniae, parvovirus, Bordetella pertussis, Rickettsia conorii and R. typhi were noted in 13.8%, 8.3%, 12.12%, 22.2%, 25%, 13% and 21.7% of cases, respectively. Acute Q fever induces a non-specific immunological arousal in a significant number of patients. This may interfere with diagnosis and delay treatment. Caution, clinical judgment and serological follow-up is warranted in such conditions.     

Antibody responses in acute and chronic Q fever and in subjects vaccinated against Q fever

An analysis is made of the antibody response to Coxiella burnettii Phase-1 and Phase-2 antigens, as measured by immunofluorescence in the IgM, IgG or IgA immunoglobulin classes, or by complement-fixation, in patients with acute and chronic Q fever and in vaccinated or skin-tested subjects. In acute (primary) Q fever, IgM specific antibodies to Phase-1 antigen are present in early convalescence together with IgM, IgG, IgA and CF antibodies to Phase-2 antigen. IgM specific antibody may persist for at least 678 days after onset of the acute illness. Patients with chronic Q fever have no IgM specific antibody to Phase-1 or -2 antigens, or only at very low levels; high levels of specific antibody in the IgG and IgA classes, together with CF antibody to both antigenic phases, appear to be characteristic. The serological response in initially seronegative, vaccinated subjects is mainly to Phase-1 antigen in the IgM fraction, and to a lesser degree to Phase-2 antigen by CF and in IgM and IgG classes. Subjects who were equivocally seropositive before vaccination showed IgA and IgG specific antibody responses to Phase-1 antigen and CF and IgG class responses to Phase-2 antigen. Similar antibody profiles were observed in patients who seroconverted after a positive skin-test. Data are also presented on the suitability of C. burnettii antigens for use in immunofluorescence and on the binding of IgM specific antibody by Phase-1 antigen but its failure to fix complement.     

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-related complications and mortality: data from a nationwide cohort

ObjectivesChronic infection with Coxiella burnetii (chronic Q fever) can cause life-threatening conditions such as endocarditis, infected vascular prostheses, and infected arterial aneurysms. We aimed to assess prognosis of chronic Q fever patients in terms of complications and mortality.MethodsA large cohort of chronic Q fever patients was assessed to describe complications, overall mortality and chronic Q fever-related mortality. Chronic Q fever-related mortality was expressed as a case fatality rate (number of chronic Q fever-related deaths/number of chronic Q fever patients).ResultsComplications occurred in 166 of 439 (38%) chronic Q fever patients: in 61% of proven (153/249), 15% of probable (11/74), and 2% of possible chronic Q fever patients (2/116). Most frequently observed complications were acute aneurysms (14%), heart failure (13%), and non-cardiac abscesses (10%). Overall mortality was 38% (94/249) for proven chronic Q fever patients (median follow-up 3.6 years) and 22% (16/74) for probable chronic Q fever patients (median follow-up 4.7 years). The case fatality rate was 25% for proven (63/249) chronic Q fever patients and 4% for probable (3/74) chronic Q fever patients. Overall survival was significantly lower in patients with complications, compared to those without complications (p <0.001).ConclusionsIn chronic Q fever patients, complications occur frequently and contribute to the mortality rate. Patients with proven chronic Q fever have the highest risk of complications and chronic Q fever-related mortality. Prognosis for patients with possible chronic Q fever is favourable in terms of complications and mortality.     

Q fever and spontaneous abortion

Q fever, caused by Coxiella burnetii, may result in abortions in infected animals and pregnant women. However, the role that Q fever plays in spontaneous abortions is still unknown. This study examined the association between Q fever serology and abortion in a region where Q fever is endemic. A case–control population-based study was conducted in General Yagüe Hospital (Burgos area, Spain) between June 2009 and July 2010. A total of 801 samples from 500 pregnant women were tested, of whom 273 had a spontaneous abortion and 227 gave birth. IgG and IgM antibody titres against Q fever were determined in their two phases (I and II) by immunofluorescence assay. Seropositivity (phase I IgG ≥1:16 or phase II IgG ≥1:80) was detected in 88/273 (32.2%) cases and 53/227 (23.3%) controls; p <0.01, OR 1.5, 95% CI 1.0–2.3. Seropositivity for both phases of IgG, compatible with recent or persistent infection, was detected in 55 (20.1%) vs 22 (9.7%); p <0.001, OR 2.3, 95% CI 1.3–3.9. High phase II IgG antibodies compatible with active or recent infection (titres ≥1:160) were detected in 27 (9.6%) vs 7 (3.1%); p <0.002, OR 3.4, 95% CI 1.4–8.0, respectively. Q fever was diagnosed in 14 (5.1%) cases. The risk of abortion associated with serological markers of active or recent Q fever in pregnant women was measurable and noticeable in this population, and accounted for 12% (95% CI 4–21%).     

Comparison of enzyme-linked immunosorbent assay and complement fixation and indirect fluorescent-antibody tests for detection of Coxiella burnetii antibody.

An enzyme-linked immunosorbent assay (ELISA) was developed to detect immunoglobulin G to Coxiella burnetii phase II. Serum samples from 213 patients who had had Q fever 1 year previously and from 301 blood donors from six localities in Switzerland were tested by ELISA and by indirect fluorescent-antibody (IFA) and complement fixation (CF) tests. The ELISA and the IFA and CF tests detected antibody to C. burnetii in 202 (94.8%), 193 (90.6%), and 166 (77.8%) of the 213 Q fever patients, respectively. With the serum samples from blood donors, the ELISA yielded a higher percentage of positive sera than did the IFA and CF tests. The high specificity of the three tests was confirmed by analyzing paired serum samples from 36 patients suffering from acute pneumonia of viral or bacterial origin. In these cases, the serological results were negative by the three tests, except for three Q-fever cases included as positive control.