%0 Journal Article
%T Serological cross-reactivity between spotted fever and typhus groups of rickettsia infection in Japan.
%A Aita T
%A Sando E
%A Katoh S
%A Hamaguchi S
%A Fujita H
%A Kurita N
%J Int J Infect Dis
%V 130
%N 0
%D May 2023
%M 36907548
%F 12.074
%R 10.1016/j.ijid.2023.03.012
%X <B>OBJECTIVE: </B>We examined the frequency of cross-reactions to Rickettsia typhi in patients with Japanese spotted fever (JSF) and evaluated the differences between two rickettsiae using antibody endpoint titers.<BR><B>METHODS: </B>Patients' immunoglobulin (Ig)M and IgG titers against Rickettsia japonica and Rickettsia typhi in two phases were measured using an indirect immunoperoxidase assay at two reference centers for rickettsiosis in Japan. Cross-reaction was defined as a higher titer against R. typhi in convalescent sera than in acute sera among patients fulfilling the criteria for JSF diagnosis. The frequencies of IgM and IgG were also evaluated.<BR><B>RESULTS: </B>Approximately 20% of cases showed positive cross-reactions. A comparison of antibody titers revealed the difficulty in identifying some positive cases.<BR><B>CONCLUSIONS: </B>Cross-reactions of 20% in serodiagnosis may lead to the misclassification of rickettsial diseases. However, with the exception of some cases, we were able to successfully differentiate JSF from murine typhus using each endpoint titer.