Significance of Q fever serologic diagnosis in clinically suspect patients

Q fever is caused by C. burnetii, an intracellular obligate bacterium. For clinical confirmation of Q fever, diagnosis of interstitial pneumonia is of significance. The acute disease varies in severity from minor to fatal, with the possibility of serious complications. Chronic endocarditis is a well-known outcome. Symptoms of Q fever can vary; fixing diagnosis is done by serology with the phase I and the phase II antibody. We tested 44 sera of 31 clinically suspect patients. From these, 22 patients were taken to the infection clinic, 8 to the pulmonary clinic, and one to the general hospital. From the 31 patients, 21 patients had one serum, 7 patients, 2 sera, and 3 patients, 3 sera. Blood samples were collected by vein puncture, and serum samples were kept at -20 degrees C until testing. All sera were processed by indirect immunofluorescent assay (IFA) Q fever IgM and IgG. Of 44 processed sera, 21 were seropositive. Specific IgM antibody was found in sera of 6 patients (19.4%), and specific IgG antibody in sera of 16 patients (51.2%). In sera of 15 clinically suspect patients (48.3%), no specific anticoxiella antibody was found. From these results we can confirm the importance of serology in laboratory diagnosis and clinical affirmation of suspect Q fever. Indirect immunofluorescent assay (IFA) is reliable and appropriate for daily, routine diagnosis of human Q fever.