All newborns should continue to be screened for abnormally low thyroid gland activity and inability to metabolise the amino acid phenylalanine, an independent panel of US health experts has reaffirmed.
Screening babies for hypothyroidism and phenylketonuria (PKU), as the conditions are called, is currently mandated in all 50 states, the US Preventive Services task force notes in a "Reaffirmation Recommendation Statement" released in the Annals of Family Medicine. The USPS first recommended that all newborns be screened for congenital hypothyroidism and PKU in 1996.
One in every 3 000 to 4 000 babies are be born with hypothyroidism, which can lead to impairment in neurological development and growth if not diagnosed and treated promptly, the task force notes in its current statement. Consequences can include "irreversible mental retardation." The condition is treated with thyroid hormone replacement, beginning within two weeks of birth.
The task force also notes that false positive tests are common, with just one in 25 positive tests confirmed to be congenital hypothyroidism. However, they add, testing premature or very small babies too early can produce false negative results, so these infants may need additional screening.
In PKU, which occurs in one in every 13 500 to 19 000 newborns, the body is unable to process phenylalanine, leading to a buildup of the amino acid that can lead to "severe mental retardation," the task force states. Treatment involves restricting phenylalanine consumption.
The USPS task force concludes that the net benefit of screening for both conditions is "substantial," that it outweighs any risks, and that the tests should continue to be provided to all newborns.