Phenylketonuria is one of the few diseases in which early diagnosis, leading to proper treatment, can prevent mental defects. With the development of the simple ferric chloride test for urinary phenylpyruvic acid, it seems reasonable to make routine tests 10,000 times to detect one affected child before clinical suspicion arises.
It has generally been taught that the urine does not become positive (ie, contain phenylpyruvic acid) until the baby is 1 or 2 months old. This posed a great problem even though the test is simple and inexpensive. At the age of 1 or 2 months the baby is no longer under hospital control, urine is not readily available, and even a simple test becomes inconvenient. However, a report in this issue of The Journal (p 720) indicates that, although the test may not be as reliable in the newborn period as later, it is nevertheless often positive. Routine testing