Immunofluorescence serology. A tool for prognosis of Q-fever.

The indirect immunofluorescence antibody test is currently the method of choice for Q-fever laboratory diagnosis. It permits the detection of IgG-, IgM-, and IgA-specific antibodies against the two phases of Coxiella burnetii. Sera from 20 cases of C. burnetii infection have been examined. Only total IgG against phase II were detected in cryptic infections. In acute Q-fever cases, the appearance of total IgG antibodies against phase I was a sign of aggravation, while IgM titers remained low. In subacute cases of Q-fever, anti-phase-I IgG titers were equal to or higher than anti-phase-II titers, and IgM against both phases were produced over a long time. Particularly high IgM titers were found in cases of granulomatous hepatitis. IgA antibodies against phase I were found in cases of Q-fever endocarditis, although the two cases that died had few or no IgA antibodies, despite very high IgG and IgM titers.