The Radioisotope Precipitation Test for Study of Q Fever Antibodies in Human and Animal Sera

The radioisotope precipitation test (RIPT) for measuring Q fever antigen-antibody reactions was used to examine various groups of human and animal sera. The specificity of the RIPT was determined by testing sera of Alaskan natives from Q fever-free areas, prevaccination sera from Q fever vaccination experiments in man and four sera from an egg-sensitive person. Only two of the sera from persons in the Alaskan group, one of whom had a strongly positive skin test, were RIPT positive. Only four of the 173 prevaccination sera were RIPT positive and no reaction was noted with the sera from an eggsensitive person. Results on the vaccine groups and those groups occupationally exposed demonstrated that the sensitivity of the RIPT is much greater in man than the complement fixation or capillary agglutination tests. The finding that there are so few cases of Q fever among exposed persons may be partly explained by the high percentage already having antibody detectable by the RIPT. The test was further applied to cattle, guinea pig and mouse sera but the increased sensitivity observed with human sera was not present with animal sera although it could be used for testing them.