Chronic Q fever.

From 1982 to 1986, sera from 36 patients suspected for chronic Q fever were submitted to serologic examination. By serology combined with clinical information, endocarditis was diagnosed in 17 cases, granulomatous hepatitis in 9 cases. 10 cases were dubious. High anti-phase I IgG titers and presence of specific IgM, particularly in cases of liver involvement, were demonstrated by the indirect immunofluorescence test (IFAT). IgA was present in all cases of endocarditis, but not in hepatitis patients. Distinction between subacute and chronic Q fever is difficult. It is advisable that every patient with subacute or chronic Q fever should be examined clinically and serologically for several years.