EFFECTS OF ANTICOAGULANTS ON THE DYE TEST FOR TOXOPLASMOSIS

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When the washed toxoplasmas are used for the dye test high percentages of modified organisms are often produced in the accessory factor saline controls. The cause of such an increasing modification of washed organisms by an accessory factor serum was proved to be attributable to loss of heparin as a result of removal of peritoneal exudate in which the anticoagulant was involved. Addition of the conventional dose of heparin to the reaction mixture resulted in increasing stainability of the washed organisms in the negative control, but produced numerous fine floccules that rendered the microscopic reading of the stained and unstained organisms so difficult. The use of Alsever's preservative or 0.15 M citrate buffer solution at pH 5.3 gave clear-cut dye test results when they were added to the reaction mixture at a proportion of 6%. EDTA-Na₂ was also proved to be effective at a low concentration such as 0.043%, but in extremely narrow dose range. As the source of the accessory factor, plasma could be successfully used as in the case of using accessory factor serum plus Alsever. The favorable effect of the plasma was attributed to the presence of Alsever in it. A blindfold comparative dye test on 10 sera between the two laboratories, NIH of U. S. A. and NIH of Japan, resulted in excellent agreement. The favorable effects of these anticoagulants were thought to be attributable to chelation of excessive amounts of Mg and Ca, thus adjusting these cations to the moderate dose levels.