1.The protein tyrosine reaction proposed in 1939 by Proske and Watson as a biochemical diagnostic test for malaria is essentially an indirect quantitative estimation of the serum euglobulin. The fraction is precipitated by sodium sulfate, after which the tyrosine chromogenic index is determined by comparison with a known tyrosine standard. In the series of cases reported in this communication the original technique was slightly modified in the interest of apparently greater accuracy.
2.Quantitative determinations of the tyrosine index in control cases and in tertian, quartan and estivo-autumnal malaria confirmed the findings of Proske and Watson that sera from malarial subjects usually have indices for euglobulin in excess of those of healthy individuals. In a few instances, especially of the tertian and estivo-autumnal varieties, the indices were normal or borderline. The high indices usually found in paretics rendered them unsuitable for use in studies of the development and course of the tyrosine reaction in induced malaria.
3.The tyrosine index was also determined in a small number of cases of various other conditions. In some of these diseases, notably leprosy, typhoid fever, granuloma inguinale and most cases of active tuberculosis, the tyrosine indices for serum euglobulin were higher than normal, which supports Proske and Watson's statement that the test is “non-specific.”
4.The number of cases studied in each of the categories reported is not large, but the results are sufficiently constant to warrant the conclusion that the potential clinical value of the protein tyrosine reaction is not great and that its value in the diagnosis of malaria is likely to be little more than supplemental.