title: Serological diagnosis of Q fever endocarditis.
abstract: The diagnosis of Q fever endocarditis cannot be made by bacterial cultures and necessitates serological identification of specific antibodies to Coxiella burnetii which stimulates mainly the production of anti-phase II antibodies during the acute disease, but primarily anti-phase I antibodies in endocarditis. Indirect microimmunofluorescence allows rapid detection of specific IgA, IgG and IgM. The results of serological analyses of 191 acute cases of Q fever were compared with those of 8 cases of Coxiella burnetii endocarditis. All sera were evaluated by complement fixation and microimmunofluorescence tests. The highest titre differences between primary Q fever and Q fever endocarditis were observed with anti-phase I IgA and IgG antibodies measured by microimmunofluorescence followed by anti-phase I antibodies measured by complement fixation tests. Antiphase I IgG and IgM titres were consistently higher than anti-phase II titres in endocarditis. The reverse is true in acute Q fever. In addition, anti-phase I IgA appeared to be diagnostic for Coxiella burnetii endocarditis. Accordingly we recommend the testing of these specific IgA, IgG, and IgM by microimmunofluorescence in cases of culture-negative endocarditis. These tests could also prove useful for following the development of Coxiella burnetii endocarditis in patients under treatment.
mesh_terms: D000907:Antibodies, Bacterial / Q000032:analysis*; D003168:Complement Fixation Tests; D003381:Coxiella / Q000276:immunology; D004697:Endocarditis, Bacterial / Q000175:diagnosis* / Q000276:immunology; D005455:Fluorescent Antibody Technique; D006801:Humans; D007136:Immunoglobulins / Q000032:analysis; D011778:Q Fever / Q000175:diagnosis* / Q000276:immunology; D012217:Rheumatoid Factor / Q000032:analysis
chemical_list: D000907:Antibodies, Bacterial; D007136:Immunoglobulins; D012217:Rheumatoid Factor