•Systematic application of testing designed to
identify individuals in a given population who are at
higher risk of having or developing a particular
disorder of or having a gene mutation for a particular
•Newest and most sophisticated of the techniques
used to test for genetic disorders.
•One of the fastest moving fields in medical science.
•Determines the risk of having or passing on a genetic
• Used to detect faulty or abnormal genes in an
• Detect some genes related to an increased risk of
• Detect some genes known to cause genetic
Genetic screening should not be performed
unless a number of conditions are met.
1. Condition to be screened for should be
2. Diagnostic methodology should be
3.The condition must be sufficiently frequent
to make the programme economically feasible.
4. The individual identified as at risk must have
some options, preferably either effective early
treatments or prenatal diagnosis.
TYPES OF SCREENING
There are three principle types of genetic
Prenatal genetic screening
Also called as fetal screening
Prenatal screening identifies disease in fetus.
It makes possible averting the unwanted birth
of a child with a genetic condition.
The purpose of prenatal diagnosis is to
detect significant defects in fetus.There is
now a variety of techniques,each of which
has unique advantages and disadvantages.
Amniocentesis is a surgical tap into the uterus to
obtain amniotic fluid.
The amniotic fluid can be analyzed to determine the
genetic status of fetus.
Initially used for the diagnosis of the disease
The procedure can be performed at 14 weeks
gestation or later. It is most commonly done
between 15-19 weeks.
• Currently the most common indication for genetic
amniocentesis is an increased abnormalities in the
• Helpful in diagnosis of open fetal defects such as
neural tube or ventral wall defects.
• Early amniocentesis is generally defined as
amniocentesis less then 14 weeks of gestation which
may lead to high risk of pregnancy loss.
Chorionic Villus Sampling
Chorionic Villus Sampling is a procedure for
It is the removal of a piece of chorion,the outer
tissue surrounding the embryo.
The tissue sample is used to analyze
chromosome ,biochemical and DNA status.
Chorionic Villus Sampling for common genetic
indications is performed at 10-12 weeks of
Percutaneous Umbilical Blood
It is a fetal blood sample test that takes
measurements of fetus blood
These results are used to clarify other test
One of the most common screening procedures
A transducer sends a sound wave that provides a
picture of the fetus.
The procedure is used to date the
pregnancy,assess structure and position of the
Maternal serum markers
alpha fetoprotein is most abundant globular serum
protein fetus. Large amounts of AFP are found in
fetal blood and fetal tissues. Increased or
decreased levels of AFP may indicate a variety of
Decreased levels of unconjugated oestrol and the
increased levels of human chorionic
gonadotropin (HCG) are associated with fetal
•Combining information from these markers provides
a more accurate estimate of fetal Down syndrome
risk than any one factor alone.
•This is commonly offered to patients at
approximately 15-18 weeks of pregnancy.
Also called pre-implantation genetic
diagnosis(PGD),is a specialized technique that
can reduce the risk of having a child with a
particular genetic or chromosomal disorder.
It is used to detect genetic changes in embryos
that were created using assisted reproductive
techniques such as in-vitro fertilization.
The usual purpose in identifying carriers is to
detect a risk for having a child with a serious
In the united states, pregnant women are
commonly offered carrier screening for sickle
trait if African American or latina,thalassaemia
trait if mediterranean,asian or African American
origin and Tay-sachs trait if Jewish.
• If the women proves to be a carrier, screening is
offered to father of the fetus, if he too is a carrier,
prenatal diagnosis is offered.
New born screening is used just after birth to
identify genetic disorders that can be used early in
Blood sample is tested for genetic disorders.
All states currently test infants for phenylketonuria
and congenital hypothyroidism.
Benefits-reduced morbidity and mortality of
children and cost savings to society.
Risks-parental anxiety about false positive results,
harm that causes parent-child relationship.
It provides a sense of relief from uncertainity and
help people make informed decisions about
managing their health care.
For eg:negative result: can eliminate need for
unnecessary checkups and screening tests in
Positive result: can direct a person toward
available prevention, monitoring an treatment
Risk of losing pregnancy because they require a
sample of amniotic fluid or tissue from around
Involves emotionl,social or financial
consequences of the test results.
Provide only limited informations about
Lack of treatment strategies for many genetic
disorders once they are diagnosed.
Should be voluntary
Only newborn screening for serious genetic
diseases is commonly mandated.
Screenee should make an informed choice, he
should be informed about not just the benefits
but also the risks and limitations.
Test result should be confidential
Both the biomedical community and the public
need to acquire a better understanding of