Evaluation of Commonly Used Serological Tests for Detection of Coxiella burnetii Antibodies in Well-Defined Acute and Follow-Up Sera

Abstract

cIn 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 convalescentphase 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.

Prevalence ofCoxiella burnetiiInfection in Humans Occupationally Exposed to Animals in Poland

“…Moreover, the decline of IgG phase II antibody titers is slower than that of IgG phase I titers, and IgG phase II antibodies are detected more often with IFA after a year (Wegdam-Blans et al 2012b). Definitive serological evidence of acute Q fever has to be based on the detection of both IgG and IgM antibodies.…”

<b><i>Coxiella burnetii</i></b> - Pathogenic Agent of Q (Query) Fever

“…High antibody titers against Phase I, which barely decrease over a period of 600 days, point to a chronic course [45,102,103]. IgM Phase II is still detectable 12 months after transmission of Coxiella in 62-83% of the blood samples [104]. …”

“…Real-time PCR with a sensitivity of 1 copy DNA has been developed [121]. Coxiella can be detected in the blood by PCR 2 weeks after transmission [104]. Further frequently used primer-binding sites for PCR include genome regions with repetitive elements and the outer membrane protein OMP [122,123,124].…”

“…Phase I and II, and IgM and IgG are determined in separate assays. ELISA was used for the identification of infected blood donors in the Netherlands, and reactive samples were further analyzed by PCR [102,104]. …”

High Coxiella burnetii DNA Load in Serum during Acute Q Fever Is Associated with Progression to a Serologic Profile Indicative of Chronic Q Fever

“…However, there is a lag in antibody responses of 7 to 15 days after the onset of symptoms, which is an important disadvantage to note for serology, as it is the primary method of diagnosis for acute Q fever (1). Another difficulty in diagnosing acute Q fever is the persistence of IgM phase II antibodies (11).…”