STATES CALLED LAX ON TESTS FOR LEAD IN POOR CHILDREN
GAO and Federal advisory panel fault most states for not complying with 1989 law requiring that young children on Medicaid be tested for lead poisoning; Medicaid recipients are three times as likely as other children to have high amounts of lead in blood; tests cost under $10 but many doctors do not believe they are necessary or are unaware of Federal requirement; many poor children are often not taken to doctor until they are sick, and most children with high levels of lead do not display obvious symptoms; Centers for Disease control says 890,000 children, about 535,000 of them in Medicaid, have toxic lead levels in blood; screenings vary widely state to state (M)