Every state in the United States mandates newborn metabolic screening. Each state determines its own priorities and procedures, but the following diseases are usually included in metabolic screening: phenylketonuria, galactosemia, congenital hypothyroidism, maple sugar urine disease, and organic aciduria (see Section 10). Many states now screen for cystic fibrosis, testing for immunoreactive trypsinogen. If that test is positive, then a deoxyribonucleic acid (commonly referred to as DNA) analysis for cystic fibrosis mutations is performed.
Children with hemoglobinopathies are at higher risk for infection and complications from anemia, which early detection may prevent or ameliorate. Infants with sickle cell disease are begun on oral penicillin prophylaxis to prevent sepsis, the major cause of mortality in these infants (see Chapter 150).
Because speech and language are central to a child’s cognitive development, the hearing screening is performed before discharge from the newborn nursery. An infant’s hearing is tested by placing headphones over the infant’s ears and electrodes on the head. Standard sounds are played, and the transmission of the impulse to the brain is documented. If abnormal, a further evaluation is indicated, using evoked response technology of sound transmission.
Hearing and Vision Screening of Older Children
Inferences about hearing are drawn from asking parents aboutresponses to sound and speech and by examining speech andlanguage development closely. Inferences about vision maybe made by examining gross motor milestones (children withvision problems may have a delay) and by physical examination of the eye. Parental concerns about vision should be sought untilthe child is 3 years of age and about hearing until the child is4 years of age. If there are concerns, definitive testing shouldbe arranged. Hearing can be screened by auditory evokedresponses, as mentioned for newborns. For toddlers and olderchildren who cannot cooperate with formal audiologic testingwith headphones, behavioral audiology may be used. Sounds ofa specific frequency or intensity are provided in a standard environment within a soundproof room, and responses are assessedby a trained audiologist. Vision may be assessed by referral to apediatric ophthalmologist and by visual evoked responses.
Children 3 Years of Age and Older
At various ages, hearing and vision should be screened objectively using standard techniques as specified in the Bright Futures’ recommendations. Asking the family and child about any concerns or consequences of poor hearing or vision accomplishes subjective evaluation. At 3 years of age, children are screened for vision for the first time if they are developmentally able to be tested. Many children at this age do not have the interactive language or interpersonal skills to perform a vision screen; these children should be re-examined at a 3to 6-month interval to ensure that their vision is normal. Because most of these children do not yet identify letters, using a Snellen eye chart with standard shapes is recommended. When a child is able to identify letters, the more accurate letter-based chart should be used. Audiologic testing of sounds with headphones should be begun on the fourth birthday (although Head Start requires that pediatricians attempt the hearing screening at 3 years of age). Any suspected audiologic problem should be evaluated by a careful history and physical examination, with referral for comprehensive testing. Children who have a documented vision problem, failed screening, or parental concern should be referred, preferably to a pediatric ophthalmologist.
Children are screened for anemia at ages when there is a higher incidence of iron deficiency anemia. Infants are screened at birth and again at 4 months if there is a documented risk, such as low birth weight or prematurity. Healthy term infants usually are screened at 12 months of age because this is when a high incidence of iron deficiency is noted. Children are assessed at other visits for risks or concerns related to anemia (denoted by a ★ in the Bright Futures’ recommendations at http://brightfutures.aap.org/clinical_practice.html ).Any abnormalities detected should be evaluated for etiology.Anemic infants do not perform as well on standard developmental testing. When iron deficiency is strongly suspected, a therapeutic trial of iron may be used (see Chapter 150).