Supplemental Newborn Screen, Blood Spot
Presymptomatic identification of disorders to allow for early initiation of treatment and consequent improvement in the long-term prognosis of affected patients.
Early diagnosis may also minimize complications and help avoid unnecessary diagnostic testing and identify families for whom prenatal genetic counseling may be helpful.
Disorders detectable by amino acid, acylcarnitine, and succinylacetone profiling using MS/MS include:
Amino Acid Metabolism
Fatty Acid Metabolism
Organic Acid Metabolism
Short-chain acyl- CoA dehydrogenase (SCAD) deficiency
Glutaric academia Type I (GA-1)
Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency
Mitochondrial trifunctional protein (TFP) deficiency
Long-chain 3-hydroxy acyl-CoA dehydro genase (LCHAD) deficiency
3-Methylcrotonyl- CoA carboxylase deficiency
Maple syrup urine disease (MSUD)
Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency
3-Methyl-glutaconyl- CoA hydratase deficiency
Phenylketonuria and other causes of hyperphenylalaninemia
Carnitine palmitoyl- transferase deficiency Type II, (CPT-2)
Multiple carboxylase deficiency
Tyrosinemia Type I
Carnitine-acylcarnitine translocase (CACT) deficiency
Tyrosinemia Type II
Glutaric acidemia Type II (GA-2; multiple acyl- CoA dehydrogenase deficiency) 2,4-Dienoyl-CoA reductase deficiency 3-Hydroxy-3- methylglutaryl-CoA (HMG-CoA) lyase deficiency
2-Methylbutyryl-CoA dehydrogenase deficiency Isobutyryl-CoA dehydrogenase deficiency
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
Panel includes all disorders recommended by the American College of Medical Genetics (Genet Med 2006;8[Supplement]:1S-11S).
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Newborn screening as a public health measure was initiated in the early 1960s for the identification of infants affected with phenylketonuria (PKU). Since then, additional genetic and nongenetic conditions were included in state screening programs. The goal of newborn screening is to detect diagnostic markers of the selected disorders in blood spots collected from presymptomatic newborns. Inherited disorders of amino acid, fatty acid, and organic acid metabolism typically manifest during the first 2 years of life as acute metabolic crises and usually result in severe neurologic impairment or death. These metabolic decompensations are usually triggered by intermittent febrile illness, such as common viral infections leading to prolonged fasting and increased energy demands. Early identification of affected newborns allows for early initiation of treatment to avoid mortality, morbidity and disabilities due to these disorders.
Tandem mass spectrometry (MS/MS) is a powerful multianalyte screening method, which is ideally suited for population-wide testing. Since the early 1990s, MS/MS has made possible the screening for more than 30 genetic disorders affecting the metabolism of amino acids, fatty acids and organic acids based on the profiling of amino acids and acylcarnitines in blood spots. In Mayoâ€™s experience, the combined incidence of the disorders identifiable by MS/MS in a single blood spot analysis is approximately 1 in 1,600 newborns.
The Secretaryâ€™s Advisory Committee on Heritable Disorders in Newborns and Children (SACHDNC) recommends 31 disorders to be screened for by all programs (available at http://www.hrsa.gov/advisorycommittees/mchbadvisory/heritabledisorders/index.html). These conditions are considered to fulfill 3 basic principles:
-Condition is identifiable at a period of time (24 to 48 hours after birth) at which it would not ordinarily be clinically detected.
-Test with appropriate sensitivity and specificity is available.
-Demonstrated benefits of early detection, timely intervention, and efficacious treatment.
In acknowledgement of the fact that screening tests do not primarily determine disease status, but measure analytes which in most cases are not specific for a particular disease, the ACMG report includes 26 conditions which did not meet all 3 selection criteria but are identified nevertheless because most of them are included in the differential diagnosis of screening results observed in core conditions (Table 1). Although these conditions do not meet all three selection criteria, the possibility of making the diagnosis early in life not only helps to avoid unnecessary diagnostic testing, but is also beneficial to the patient's families because genetic counseling and prenatal diagnosis can be offered for subsequent pregnancies.
Supplemental newborn screening by MS/MS as described here does not replace current state screening programs, because MS/MS does not allow primary screening for galactosemia, congenital hypothyroidism, congenital adrenal hyperplasia (CAH), cystic fibrosis, biotinidase, sickle cell disease, severe combined immune deficiency (SCID), critical congenital heart disease, and congenital hearing loss.
The simultaneous MS/MS analysis of amino acids, acylcarnitines, and succinylacetone in dried blood spots can be performed in 3 minutes per specimen, generating metabolite profiles that allow for the biochemical diagnosis of multiple disorders. This is in contrast to conventional screening techniques traditionally based on the principle of 1 separate test for each disorder. The performance of Mayo's supplemental newborn screening program is characterized by a very low false-positive rate of 0.075% and a high positive predictive value of 46%.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
The quantitative measurements of the various amino acids, acylcarnitines, and succinylacetone support the interpretation of the complete profile but for the most part are not diagnostic by themselves. The interpretation is by pattern recognition. Abnormal results are not sufficient to conclusively establish a diagnosis of a particular disease. To verify a preliminary diagnosis, independent biochemical (ie, in vitro enzyme assay) or molecular genetic analyses are required, many of which are offered within the Department of Laboratory Medicine and Pathology Division of Laboratory Genetics.
The reports will be in text form only, values for the more than 60 analytes and analyte ratios will not be provided. A report for a normal screening result will be reported as: "In this blood spot sample, the amino acid and acylcarnitine profiles by tandem mass spectrometry showed no biochemical evidence indicative of an underlying metabolic disorder."
A report for an abnormal screening result will include a quantitative result of the abnormal metabolites, a detailed interpretation of the results, including an overview of the results' significance, possible differential diagnoses, recommendations for additional biochemical testing and confirmatory studies (enzyme assay, molecular analysis), a phone number for one of the contacts at the Mayo Clinic, and a phone number for one of the laboratory directors if the referring physician has additional questions.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Testing is only appropriate for patients <1 week of age as part of prospective newborn screening.
This test is supplemental and not intended to replace state mandated newborn screening.
Test is not appropriate for metabolic screening of symptomatic patients.
In a few instances, falsely abnormal results may occur in the analysis of amino acid and acylcarnitine profiles. To keep the number of false-positive and false-negative results to a minimum, results are interpreted based on the metabolite profiles, the information provided on the newborn screening card, and second tier tests for several nonspecific analytes. Using this approach our false-positive rate is only 0.075%.
Newborns discharged on the first day of life will need to be retested during the first week of life, eg, at the first well-child examination, as is customary for state-mandated newborn screening programs. This is necessary to avoid false-negative amino acid results due to limited protein intake on the first day of life.
Carrier status (heterozygosity) for inborn errors of metabolism cannot be reliably detected by amino acid and acylcarnitine profiling.
The performance of Mayo's supplemental newborn screening program is characterized by a very low false-positive rate of 0.072% (cumulative for 2004-2011; 2011 YTD is 0.055%) and a high positive predictive value of 47% (2011 YTD 49%). The positive detection rate is 1 affected case in 1,583 babies screened (n=505,017).
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Matern D:Tandem mass spectrometry in newborn screening. Endocrinologist 2002;12:50-57
2. Rinaldo P, Tortorelli S, Matern D:Recent developments and new applications of tandem mass spectrometry in newborn screening. Curr Op Peditr 2004;16:427-433
3. Rinaldo P, Zafari S, Tortorelli S, Matern D:Making the case for objective performing metrics in newborn screening by tandem mass spectrometry. MRDD Res Rev 2006;12:255-261
4. Matern D, Tortorelli S, Oglesbee D, et al:Reduction of the false-positive rate in newborn screening by implementation of MS/MS-based second-tier tests:The Mayo Clinic experience (2004-2007). J Inherit Metab Dis 2007;30(4):585-592
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
- Request for Original Newborn Screening Card
- Newborn Screening Follow-up for Isolated C4 Acylcarnitine Elevations (also applies to any plasma C4 acylcarnitine elevations)
- Newborn Screening Follow-up for Elevations of C8, C6, and C10 Acylcarnitine (also applies to any plasma C8, C6, and C10 acylcarnitine elevations)
- Newborn Screening Follow-up for Isolated C5 Acylcarnitines Elevations (also applies to any plasma C5 acylcarnitine elevation)