SERODIAGNOSIS OF TOXOPLASMOSIS - A COMPAR ATIVE MULTICENTER STUDY OF A SERIES OF CONTROL SERA USING VARIOUS CURRENTLY AVAILABLE TESTS AND EXPRESSION OF THE RESULTS IN INTERNATIONAL UNITS

Reported are the results of a multicentre study involving 40 laborator ies that was carried out in France to assess all the currently availab le methods used for the serodiagnosis of toxoplasmosis. For this purpo se 10 batches of control sera were prepared with titres in the range 0 -260 IU per ml. These sera were tested in nine laboratories using immu nofluorescence methods; in three laboratories using dye tests; in fort y laboratories using enzyme-linked immunosorbent assay; in four labora tories using direct agglutination and haemagglutination; in seven labo ratories using the high-sensitivity IgG agglutination test; and in thr ee laboratories using the latex agglutination test. in this way, 70 se ries of titrations were carried out using seven procedures and the res ults were compared with those obtained using the WHO reference serum i n 15 cases, with the French national E6 serum in 16 other cases, and i n 39 cases using 15 reference sera supplied by the reagent manufacture rs. Rigorous comparison of the tests was not possible in all cases bec ause one aim of the study was to ensure that the tests were carried ou t under the usual working conditions that prevailed in the participati ng laboratories. The results obtained indicate that the serological te sts currently available for toxoplasmosis are acceptable for its serod iagnosis. Presentation of the titres in IU has advantages; however, ca ution is required since the definition of IU varies according to the t est and reagents used. it is therefore essential that the conditions a nd limits for a positive reaction be carefully defined in each case, e specially for commercially available kits.