D. Hsia, J. Dobson
May 2, 1970
Abstract Of 90 infants included in a collaborative study of phenylketonuria (P.K.U.) 60 were males and 30 were females. The method of ascertainment seems to have played a part in this altered sex ratio since the high proportion of males was found only in series ascertained by screening alone. In this series there were 7 cases (all female) in which the rise in blood-phenylalanine was delayed. Such cases would be missed in routine screening in the first forty-eight hours of life. Another explanation could be that one published series of P.K.U. (near-normal I.Q.) contained an excess of females, and such cases might escape detection. It is suggested that the Guthrie test be repeated later than forty-eight hours after birth and that plasma-phenylalanine levels be measured serially in at-risk infants.