Guthrie test Test for a number of genetic diseases (especially phenylketonuria) based on measuring the concentrations of amino acids in a small sample of blood taken by pricking the heel of the child a few days after birth, by biological assay using mutated bacteria.

Guthrie test (heel-prick blood test) (guth-ri) n. a blood test performed on all newborn babies at the end of the first week of life. It can detect several inborn errors of metabolism (including phenylketonuria), hypothyroidism, and cystic fibrosis (the last is not routinely offered). [ R. Guthrie (1916–95), US paediatrician]