newborn screening newborn screening newborn screening (nbs) is a public health program of screening in infants shortly after birth for conditions that are treatable, but not clinically evident in the newborn period. the goal is to identify infants at risk for these conditions early enough to confirm the diagnosis and provide intervention that will alter the clinical course of the disease and prevent or ameliorate the clinical manifestations. nbs started with the discovery that the amino acid disorder phenylketonuria (pku) could be treated by dietary adjustment, and that early intervention was required for the best outcome. infants with pku appear normal at birth, but are unable to metabolize the essential amino acid phenylalanine, resulting in irreversible intellectual disability. in the 1960s, robert guthrie developed a simple method using a bacterial inhibition assay that could detect high levels of phenylalanine in blood shortly after a baby was born. guthrie also pioneered the collection of blood on filter paper which could be easily transported, recognizing the need for a simple system if the screening was going to be done on a large scale. newborn screening around the world is still done using similar filter paper. nbs was first introduced as a public health program in the united states in the early 1960s, and has expanded to countries around the world. newborn screeningmeshd015997medlineplus007257 screening programs are often run by state or national governing bodies with the goal of screening all infants born in the jurisdiction for a defined panel of treatable disorders. the number of diseases screened for is set by each jurisdiction, and can vary greatly. most nbs tests are done by measuring metabolites or enzyme activity in whole blood samples collected on filter paper. bedside tests for hearing loss using automated auditory brainstem response and congenital heart defects using pulse oximetry are included in some nbs programs. infants who screen positive undergo further testing to determine if they are truly affected with a disease or if the test result was a false positive. follow-up testing is typically coordinated between geneticists and the infant's pediatrician or primary care physician. history robert guthrie is given much of the credit for pioneering the earliest screening for phenylketonuria in the late 1960s using a bacterial inhibition assay (bia) to measure phenylalanine levels in blood samples obtained by pricking a newborn baby's heel on the second day of life on filter paper. congenital hypothyroidism was the second disease widely added in the 1970s. guthrie and colleagues also developed bacterial inhibition assays for the detection of maple syrup urine disease and classic galactosemia. the development of tandem mass spectrometry (ms/ms) screening in the early 1990s led to a large expansion of potentially detectable congenital metabolic diseases that can be identified by characteristic patterns of amino acids and acylcarnitines. in many regions, guthrie's bia has been replaced by ms/ms profiles, however the filter paper he developed is still used worldwide, and has allowed for the screening of millions of infants around the world each year. in the united states, the american college of medical genetics recommended a uniform panel of diseases that all infants born in every state should be screened for. they also developed an evidence-based review process for the addition of conditions in the future. the implementation of this panel across the united states meant all babies born would be screened for the same number of conditions. this recommendation is not binding for individual states, and some states may screen for disorders that are not included on this list of recommended disorders. prior to this, babies born in different states had received different levels of screening. on april 24, 2008, president george w. bush signed into law the newborn screening saves lives act of 2007. this act was enacted to increase awareness among parents, health professionals, and the public on testing newborns to identify certain disorders. it also sought to improve, expand, and enhance current newborn screening programs at the state level. inclusion of disorders newborn screening programs initially used screening criteria based largely on criteria established by jmg wilson and f. jungner in 1968. although not specifically about newborn population screening programs, their publication, principles and practice of screening for disease proposed ten criteria that screening programs should meet before being used as a public health measure. newborn screening programs are administered in each jurisdiction, with additions and removals from the panel typically reviewed by a panel of experts. the four criteria from the publication that were relied upon when making decisions for early newborn screening programs were: having an acceptable treatment protocol in place that changes the outcome for patients diagnosed early with the disease an understanding of the condition's natural history an understanding about who will be treated as a patient a screening test that is reliable for both affected and unaffected patients and is acceptable to the public as diagnostic techniques have progressed, debates have arisen as to how screening programs should adapt. tandem mass spectrometry has greatly expanded the potential number of diseases that can be detected, even without satisfying all of the other criteria used for making screening decisions. duchenne muscular dystrophy is a disease that has been added to screening programs in several jurisdictions around the world, despite the lack of evidence as to whether early detection improves the clinical outcome for a patient. targeted disorders