Complement fixation reaction in toxoplasmosis.

In toxoplasmosis serodiagnosis the complement fixation reaction (CF) is barely sensitive and specific and supplies results below the general standard levels of this technique. The reasons for this deficiency are discussed and detected in the preparation modalities of the toxoplasma antigens. Two diagnostic antigens are prepared and evaluated; the former, a suspension of whole toxoplasma (WT) the latter a total extract of toxoplasma (TET). The antigens are characterized by the preparative process, culture host and the extractive technique with a modified ultrasonic disintegrator. The antigens are used in the CF reaction, performed with the modified LBCF method, with a 100% hemolysis reading (H 100). The LBCF-H 100 reaction with WT and TET antigens is evaluated parellely to the indirect immunofluorescence reaction (IF) and dye test (DT) on 2514 human sera from cases os suspected toxoplasmosis and pregnant women. The analysis of the serological results pointed out that the LBCF-H 100 reaction performed with WT antigen, shows a sensitivity and specificity equivalent to that of the DT. The LBCF-H 100 reaction with TET antigen extends the range of the antibodies detectable with WT antigen. The optimal serological combination to identify the highest number of seropositive cases of toxplasma infection is given by LBCF-TET and IF reactions.