COMPARISON OF THE COMPLEMENT-FIXATION, INDIRECT FLUORESCENT-ANTIBODY, AND MICROAGGLUTINATION TESTS FOR THE SEROLOGICAL DIAGNOSIS OF RICKETTSIAL DISEASES

Three techniques for the serological diagnosis of Rocky Mountain spotted fever (SF) were compared by testing 417 sera from 178 patients who probably did not have rickettsial infections and 88 sera from 41 patients who probably had SF. The techniques were complement fixation (CF), indirect fluorescent antibody (IFA), and microagglutination (MA). To avoid possible degradation during unnecessary purification, the antigens [Ag] were prepared by the most simple methods possible. In the CF tests of 417 sera from patients with nonrickettsial diseases there was only 1 titer of 8 and none at higher dilutions, whereas with the IFA and MA tests 4-8% of the sera reacted with SF Ag and 4-20% reacted with murine typhus (MT) Ag; these reactions were probably not caused by specific rickettsial antibody. With the SF sera, the IFA test was the most sensitive and the MA test was the least sensitive at each interval after infection. The IFA results showed the least number of confusing cross-reactions with MT Ag and the MA test showed the most. The relative advantages of the 3 tests in serodiagnosis of rickettsial diseases are discussed.