Assessment of the PKU card as a retrospective index of neonatal blood lead status.

PKU cards were obtained for 50 one-year-old children whose cord blood lead, maternal blood lead and household water lead were known. These 3 values are known to correlate well. Lead values were measured from the blood on the cards, and correlated significantly with the other values. However, predictive validity was poor due to card contamination and it is felt that, for the individual patient, this is not a reliable retrospective index of blood lead at the time of birth.