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Drops of blood, filter paper, bacteria, a bacterial inhibitor, and a baking dish—that’s all it took for microbiologist Robert Guthrie to develop a basic test for phenylketonuria, a genetic metabolic disease that, if left untreated in infants, soon leads to neurological dysfunction and intellectual disability. The test would lay the foundation for screening newborns for diseases.
In 1957, Guthrie met Robert Warner, a specialist who diagnosed individuals with mental disabilities. Warner told Guthrie about phenylketonuria (PKU), now known to affect roughly 1 in 10,000 children. The disease makes it impossible to break down the amino acid phenylalanine, so that it builds up to toxic levels in the body and disrupts neuronal communication. Once a child was diagnosed, a strict low-phenylalanine diet could prevent further damage, but Warner had no easy way to measure phenylalanine levels in his PKU patients’ blood to monitor the diet’s effects. He ...
