Sabin-Feldman Dye Test for Toxoplasmosis

The Use of Sodium Citrate in Accessory Factor, and a Method for Collecting and Storing Blood on Paper Discs

Gordon D. WallacePacific Research Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, P. O. Box 1680, Honolulu, Hawaii 96806

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The addition of sodium citrate to certain accessory-factor (AF) serum samples for inclusion in the Sabin-Feldman dye test decreased the proportion of nonstaining Toxoplasma from unacceptable to acceptable levels. This procedure also made easier the location of suitable AF donors, and eliminated the problem of a precipitate, frequently encountered in plasma intended for use as AF. A paper-disc method for collecting and storing blood for antibody determination was proved to be highly accurate for use in the dye test by comparing the titer of eluate from filter-paper discs containing capillary blood with the titer of serum from venous blood collected from a group of blood donors. It was also observed that blood on filter-paper discs usually could be stored for several weeks at room temperature without appreciable loss of antibody titer. Furthermore, it was demonstrated experimentally that accurate antibody determinations could be made from discs containing blood of rats collected several hours after death.