<P> Newborn screening samples are collected from the infant between 24 hours and 7 days after birth, with the requirement that the baby has fed at least once . Samples can be collected at the hospital, or by midwives . If a sample is collected from an infant who is less than 24 hours old, the laboratory will often request a repeat specimen be taken after 24 hours . Samples are mailed daily to the laboratory responsible for testing . In the United States and Canada, newborn screening is mandatory, with an option for parents to opt out of the screening in writing if they desire . In most of Europe, newborn screening is done with the consent of the parents . Proponents of mandatory screening claim that the test is for the benefit of the child, and that parents should not be able to opt out on their behalf . In regions that favour informed consent for the procedure, they report no increase in costs, no decrease in the number of children screened and no cases of included diseases in children who did not undergo screening . </P> <P> Because newborn screening programs test for a number of different conditions, a number of different laboratorial methodologies are used, as well as bedside testing for hearing loss using evoked auditory potentials and congenital heart defects using pulse oximetry . Newborn screening started out using simple bacterial inhibition assays to screen for a single disorder, starting with phenylketonuria in the early 1960s . With this testing methodology, newborn screening required one test to detect one condition . As mass spectrometry became more widely available, the technology allowed rapid determination of a number of acylcarnitines and amino acids from a single dried blood spot . This increased the number of conditions that could be detected by newborn screening . Enzyme assays are used to screen for galactosemia and biotinidase deficiency . Immunoassays measure thyroid hormones for the diagnosis of congenital hypothyroidism and 17α - hydroxyprogesterone for the diagnosis of congenital adrenal hyperplasia . Molecular techniques are used for the diagnosis of cystic fibrosis and severe combined immunodeficiency . </P> <P> The goal is to report the results within a short period of time . If screens are normal, a paper report is sent to the submitting hospital and parents rarely hear about it . If an abnormality is detected, employees of the agency, usually nurses, begin to try to reach the physician, hospital, and / or nursery by telephone . They are persistent until they can arrange an evaluation of the infant by an appropriate specialist physician (depending on the disease). The specialist will attempt to confirm the diagnosis by repeating the tests by a different method or laboratory, or by performing other corroboratory or disproving tests . The confirmatory test varies depending on the positive results on the initial screen . Confirmatory testing can include analyte specific assays to confirm any elevations detected, functional studies to determine enzyme activity, and genetic testing to identify disease - causing mutations . In some cases, a positive newborn screen can also trigger testing on other family members, such as siblings who did not undergo newborn screening for the same condition or the baby's mother, as some maternal conditions can be identified through results on the baby's newborn screen . Depending on the likelihood of the diagnosis and the risk of delay, the specialist will initiate treatment and provide information to the family . Performance of the program is reviewed regularly and strenuous efforts are made to maintain a system that catches every infant with these diagnoses . Guidelines for newborn screening and follow up have been published by the American Academy of Pediatrics and the American College of Medical Genetics . </P> <P> Newborn screening programs participate in quality control programs as in any other laboratory, with some notable exceptions . Much of the success of newborn screening programs is dependent on the filter paper used for the collection of the samples . Initial studies using Robert Guthrie's test for PKU reported high false positive rates that were attributed to a poorly selected type of filter paper . This source of variation has been eliminated in most newborn screening programs through standardization of approved sources of filter paper for use in newborn screening programs . In most regions, the newborn screening card (which contains demographic information as well as attached filter paper for blood collection) is supplied by the organization carrying out the testing, to remove variations from this source . </P>

Criteria for including a disorder on a metabolic screening panel