Newborn metabolic screen (blood spot, urine)
General: Details of specific screening tests routinely performed vary from state to state and among industrialized countries, and a newborn screen may include tests for non-metabolic disorders. Typical screens are collected on a filter paper card as a "blood spot," although standardized screening of urine has also been done (largely abandoned due to difficulty of regularly & safely obtaining a clean sample, as well as low sensitivity & specificity). Blood spot cards are most useful in full term infants with normal Hb/Hct, but can be less accurate in pre-term infants with abnormal Hct. Type of feeding at the time of obtaining sample may also alter results.
Modern newborn screens may include:
- amino acid disorders
- organic acidemias
- fatty acid oxidation disorders
- carnitine disorders
- congenital adrenal hypoplasia
- galactosemia
- lysosomal storage diseases
- biotinidase deficiency
- hypothyroidism
Differential Diagnosis:
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