The Guthrie Test – Christmas Lectures with Walter Bodmer

All newborns have this so called Guthrie test. Now I’ve got an example to show you here. Which we’re grateful for the Great Ormond
Street people for giving us. You see, you take just a heel prick, a little blood from the newborn baby. And you put it on a bit of blotting paper
like this. And you can have the patient’s name and all
the information there. And when the blotting paper is dry, it can
just be sent through the post. Because what you’re testing for in this blood, is the level of that aminoacid that can’t
be metabolised. And that survives the post perfectly well. So what you do is, when it goes to the testing
laboratory, you punch out a little bit of that paper that
has the blood sample in it. And then what you do, is you put that bit
of paper onto bacteria on a plate. And I’ve got a sample plate here. And the bacteria are treated in such a way that they’ll only grow if they’re given phenylalanine. So they’ll only grow around the bit of paper that has phenylalanine in it. Now these are test spots here. And you can see that halo of growth of the
bacteria there. Those are the test ones. And can you see one positive result on that
plate? You see that one? That one there? See it there? That’s a positive result. The amino acid from that little bit of filter
paper has spread around and allowed the bacteria
to grow. It’s a very simple straightforward test that’s
done on everybody now. It’s been done since the 1960s. So all newborns can be screened to see whether they’ve got that disease.

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