Pediatric emergency medicine trisk 2453 2453
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All neonates with a positive NBS require evaluation and confirmatory testing. Those with
NBS positive for a condition that may result in decompensation in the neonatal period require
emergent evaluation even if they appear to be asymptomatic.
Most neonates with a positive NBS will have a false-positive result.
Evaluation should include history and physical examination, and IEM-specific routine
laboratory tests to reveal clinical manifestation or confirm absence of findings.
Confirmatory NBS tests should be sent even if routine laboratory tests are normal.
Evaluation, management, and disposition should be in consultation with an IEM specialist.
Management should include correction of any metabolic derangements, assuring adequate
hydration and avoidance of potentially toxic substances even in asymptomatic patients.
Goals of Treatment
Treatment goal is to confirm NBS and to prevent symptoms and metabolic derangements of IEM.
Current Understanding
The Advisory Committee on Heritable Disorders in Newborns and Children, as of July 2018,
recommends that states screen for a core panel of 35 conditions, 24 of which are IEMs, and an additional
26 conditions that are considered secondary targets on the basis of more mild symptoms and/or absence
of treatment options, of which 24 are IEMs. Most, but not all states, now screen for core conditions, and
at least some of the secondary targets ( ).
For every true-positive NBS, there are 12 to 60 false positives. To minimize the number of falsenegative NBS results, cutoff values have been deliberately set low with a national goal of an overall 0.3%
false-positive rate and a 20% positive predictive value. False positives also occur because of maternal
IEM, which, in some cases is undiagnosed. Even in the asymptomatic neonate, a false positive cannot be
assumed. Evaluation should include history, physical examination, and routine laboratory tests to reveal
clinical manifestations of disease or confirm absence of manifestations. The IEMs most likely to cause
acute decompensation in neonates include certain forms of tyrosinemia, organic acidemias, urea cycle
defects, galactosemia, and, less commonly, biotinidase deficiency. Manifestations and treatment of these
conditions are detailed in the section of this chapter on known IEMs, and for congenital adrenal
hyperplasia in Chapter 89 Endocrine Emergencies . Evaluation and management of neonates with
positive NBS should be in consultation with a metabolic specialist, or endocrinologist in the case of
congenital adrenal hyperplasia, and guided by American College of Medical Genetics NBS condition
specific ACTion sheets and confirmatory algorithms, which provide an overview of the condition and
information about potential clinical manifestations, and appropriate routine and confirmatory laboratory
tests ( ).
The New England Consortium website includes descriptions of some of the diseases in their acute
illness
protocols
( />).
Descriptions of specific IEMs can also be found in texts referenced at the end of this chapter and on
various websites, including the National Center for Biotechnology Information’s “Online Mendelian
Inheritance in Man” website ( ).
Clinical Considerations
Triage
Triage should be based on symptoms. Patients with even subtle symptoms should be expedited for care.
Assessment
