I have read the increasing spate of correspondence dealing with phenylketonuria.
It would seem that the writers have already assumed that universal testing of newborns is necessary and only ask how. I practice in a town of 20,000. In practical terms this means that I would probably test for this disease for a lifetime and discover one case. Would the vast expenditure of time and money be worth it? To carry the testing program further, why not test for mucoviscidosis with a routine sweat test?