[Rheumatoid factors : a cause of non-specific results in IgM antitoxoplasma fluorescent tests (author's transl)].

This paper confirms the finding that rheumatoid factor (RF) can cause non-specific fluorescence in fluorescent-antibody tests for toxoplasmosis carried out with IgM antiserum (Remington test). There is a 20 to 25 p. cent risk of such error, depending on the conditions under which the test is read. Elimination of the risk by the subjection of all sera to preliminary absorption, as proposed by Camargo et al., does not seem justified as the proportion of positive Remington tests is very low in France (approximately 1,5 of every 1000 sera tested) and the work involved would be wasted is most cases. What is proposed here is to tackle the problem at the other end by taking every serum with a positive response to the Remington test, testing it for RE, absorbing it on heat-aggregated human globulin of placental origin, and determining its IgM toxoplasma antibody titre again.