title: Serology in chronic Q fever is still surrounded by question marks.
abstract: 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.
authors.affiliation: Department of Medical Microbiology, Laboratory for Pathology and Medical Microbiology (PAMM), de Run 6250, 5504 DL, Veldhoven, The Netherlands, m.wegdam@pamm.nl.
authors.forename: M C A
authors.initials: MC
authors.lastname: Wegdam-Blans
authors.forename: H T
authors.initials: HT
authors.lastname: Tjhie
authors.forename: J M
authors.initials: JM
authors.lastname: Korbeeck
authors.forename: M N
authors.initials: MN
authors.lastname: Nabuurs-Franssen
authors.forename: L M
authors.initials: LM
authors.lastname: Kampschreur
authors.forename: T
authors.initials: T
authors.lastname: Sprong
authors.forename: J A W
authors.initials: JA
authors.lastname: Teijink
authors.forename: M P
authors.initials: MP
authors.lastname: Koopmans
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood*; D003168:Complement Fixation Tests / Q000379:methods*; D016997:Coxiella burnetii / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005455:Fluorescent Antibody Technique; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D011778:Q Fever / Q000175:diagnosis* / Q000276:immunology*; D012680:Sensitivity and Specificity
chemical_list: D000907:Antibodies, Bacterial; D007070:Immunoglobulin A; D007074:Immunoglobulin G