A Rapid Technique for Concentration of Urinary Chorionic Gonadotrophin for Pregnancy Testing *

False negative reactions in pregnancy testing with frogs and toads can be avoided by concentrating the urinary chorionic gonadotrophin. If unconcentrated urines are used, the incidence of these reactions may be as high as 43.7 per cent' and 50 per cent.8 Inaccuracy occurs most frequently during the late summer and early autumn months when many batrachians are relatively insensitive, and also when urinary chorionic gonadotrophin titers are low, in very early pregnancies, and in the latter half of gestation. To be useful, a concentration technique must be simple to perform and provide adequate recovery of the hormone. Furthermore, the final concentration product must be non-toxic and must not produce false positive reactions.