Neonatal Screening

criteria for disorder selection

  • relatively "high" incidence
  • treatment available
  • good assay
  • low cost/cost effective

change in paradigm about what to screen

screen only for what was treatable was philosophy until very recently
 
with advent of technology that enables detection of many conditions for which there are no cures, thinking is changing; detection allows increases demand more research into that disease and opens opportunity for genetic counseling for the family

examples of screened disorders in maryland

  • biotinidase deficiency
  • CAH
  • hypothyroidism
  • sickle cell disease
  • PKU
  • homocystinuria
  • MSUD
  • MMA
  • CF

Goal of screening tests

distinguish those who probably have the disease from those who probably do not have it

qualities of a "good" screening test

  • accurate
  • reproducible
  • inexpensive
  • non-invasive
  • uses a sensitive, specific indicator
  • high positive predictive value

parameters for assessing screening tests

  • sensitivity: how well can it predict positives

  • specificity: how well can it predict negatives

  • predictive value: frequency of accuracy in positive or negative test results
    • positive
    • negative

sensitivity of a screening test

TRUE POSITIVES

__________________

 

ALL THOSE w/ DISEASE

Specificity of screening test

TRUE NEGATIVES

__________________

 

ALL THOSE WITHOUT DISEASE

+ PREDICTIVE VALUE OF A SCREENING TEST

TRUE POSITIVES

 _____________________

 

ALL POSITIVES

– PREDICTIVE VALUE OF A SCREENING TEST

TRUE NEGATIVES

____________________

 

ALL NEGATIVES

newborn screening process

  • voluntary (refusal must be documented)
  • specimen collected after 24 hrs of breastfeeding
  • very short post-partum stays (<24hrs) interfer with screening’s accuracy for many disorders; increases markedly with slightly older newborns

tandem mass spectrometry (MS.MS)

multiplex testing technology that can provide information on a range of disorders at once
;
urea cycle disorders
organic acidurias
fatty acid oxidation disorders (MCAD actually requires this type of test for detection)
;
good technique for sorting and quantitating molecules that contain a comon fragment

informed dissent

in vast majority of states, parents have to OPT OUT of newborn screening.

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