A passive hemagglutination test for diagnosis of trench fever due to Rochalimaea quintana

A passive hemagglutination test devised for diagnosis of trench fever was easily performed and highly sensitive and specific. Tanned sheep erythrocytes were sensitized with soluble antigen from Rochalimaea quintana. The test detected antibody in six of seven cases of primary infection and in four cases of late, relapsed trench fever. Titers of antibody ranged from 1:20 to 1:640. Although both IgM and IgG antibody to R. quintana were detected by passive hemagglutination, IgG appeared to be the major reactive antibody. Antigens involved in the reaction were two types of proteins, one inactivated at 50 C and 60 C and the other at 80 C and 100 C. Of 322 control samples of sera that were tested, only one reacted positively; thus, the test had a specificity of greater than 99%. The single positive reaction was in serum from a patient with Q fever. This finding suggests that, in an area where Q fever is endemic, this disease must be ruled out in the interpretation of a positive passive hemagglutination test. Sera should be tested routinely against tanned, unsensitized erythrocytes, since an occassional sample of serum may agglutinate unsensitized cells. Because of its sensitivity and specificity, as well as its simplicity of performance, the passive hemagglutination test shows promise as a useful procedure for serologic identification of both acute and past infection with R. quintana.