Neonatal And Perinatal Screening Of Metabolic Disorder

Question 1

Examples of metabolic disorders

Answer 1

Phenyl ketonuria
Congenital hypothyroidism
Cystic fibrosis
Sickle cell disease and thalassemia 
Galactosemia
Glucose-phosphate dehydrogenase
Congenital adrenal hyperplasia

Question 2

Types of screening for in born metabolic disorder

Answer 2

Neonatal (1-28days)

Perinatal

Question 3

Factors affecting choice of disease to be screened

Answer 3

Prevalence of the disease
Technology available
Cost Implication

Question 4

Qualities of an ideal neonatal screening program

Answer 4

• The disease should not be apparent at the time of screening
• The disease should have a relatively high incidence in the
  population
• The disease should be treatable or early treatment should improve
  outcome
• The result of the test should be out in time before irreversible damage
  occurs
• The test should be simple and reliable
• The cost of treatment should ideally be offset either partly or
  completely by the cost of savings resulting from early treatment

Question 5

Screening in US

Answer 5

• Babies are screened on days 5-8
• Capillary blood samples gotten from heel prick stab is used
• Blood is placed on on paper card or blood spots
• It is posted to regional specialist labs for analysis

Question 6

Technique for analysis of samples

Answer 6

DNA analysis

Tandem Mass Spectrometry

Question 7

Prenatal Screening

Answer 7

It is usually done for high risk individuals eg screening for Tay Sach disease among Ashkenazi Jews

Question 8

Aims of prenatal screening

Answer 8

• Plan place and method of delivery
• Plan treatment options
• counseling for present and future pregnancies
• For considering options for termination of pregnancy

Question 9

How is prenatal screening done

Answer 9

It is done using fetal fibroblast obtained thus:

• 1st trimester (10-12weeks) by chorionic villus sampling
• 2nd trimester (16-20 weeks) by amniocentesis

Question 10

What other uses exists for prenatal screening aside screening for in-born metabolic disorders

Answer 10

They can be used to access Fetal Health particularly in conditions like
-Neural tube defects and
-Chromosomal abnormalities associated with metabolic disorders like trisomy 21…Down syndrome
Trisomy 18…Edward syndrome
Trisomy 13….Patau’s Syndrome

Question 11

Any other methods for prenatal screening?

Answer 11

Yea, others include assaying analyses from maternal blood, maternal urine and amniotic fluid

Question 12

What analytes are monitored

Answer 12

Alpha fetoprotein
Acytylcholinesterase
Unconjugated estriol

Question 13

Examples of biochemical analytes that can be used for fetal health assessment

Answer 13

Human chorionic gonadotropin, unconjugated estriol, alpha fetoprotein, human placental lactogen, acytylcholinesterase, lecithin, bilirubin and ADAM 12

Question 14

Short notes on alpha fetoprotein

Answer 14

-amniotic fluid and maternal serum
-screening advocated for 16-18weeks
-amniotic fluid alpha fetoprotein alone is not diagnostic because of false positives
Clinical Uses
Neural tube defects…increased levels
Down’s syndrome …decreased levels
Edward syndrome …decreased levels

Question 15

Short Notes on acytylcholinesterase

Answer 15

-Neural enzyme with high concentrations in CSF
-Increased levels in neural tube defects
-Essentially used to substantiate elevated levels of alpha fetoprotein in fluids
Clinical Use
It is used in combination with alpha fetoprotein
High amniotic fluid alpha fetoprotein + high amniotic fluid acytylcholinesterase is diagnostic of neural tube disease

Question 16

Need for screening

Answer 16

Early diagnosis is very important to prevent life threatening or irreversible clinical consequences. And it’s very important for genetic counseling and prevention where there is no treatment or cure
In summary, it is important for early diagnosis and prevention