What are options available for sScreening and prenatal diagnosis in India?

1.    Public 

2.    Private sectors 

What are difficulties in Screening and prenatal diagnosis of congenital abnormalities?

No adequate information about:

  1. Correct test 
  2. Appropriate time for ordering the test 
  3. Expertise for pre-test and post-test counselling
  4. Availability of numerous screening options with varied detection rates & costs 

NEED FOR PROGRAM FOR ANTENATAL SCREENING

In India, a population-based government program for antenatal screening is not available.

Prevalence of Down syndrome, beta-thalassaemia and NTDs in India is sufficient to appreciate the need for population-based screening for these disorders in India. 

An approximate of 21,400 children with Down syndrome, 9000 with beta-thalassaemia and 5200 with sickle cell disease are born in India every year.  

BETA-THALASSAEMIA 

There is high burden of the disease and carrier rate in India 

SCREENING TEST AND TIMING OF THE TEST FOR THALASSAEMIA AND HAEMOGLOBINOPATHIES:  

WHAT IS BEST TIME TO SCREEN?

  1. Pre-pregnancy 
  2. First antenatal visit in the first trimester  

IS PREMARITAL SCREENING ADVISED?

Not advocated. (May also stigmatize individuals causing problems with marriage proposals) 

Is Screening of adolescents or college-going students advised? 

No, it is not advised for adolescents and college-going students.

Screening of asymptomatic children for carrier status is not ethically correct and should not be done. 

What is screening test?

Cation Exchange High-Performance Liquid Chromatography (CE-HPLC)  

Describe prenatal screening for hemoglobinopathies?

Identification of mutation in both partners Husband and wife should be tested simultaneously

Scheduled in the first antenatal visit in the first trimester, 

preferably before eight weeks of gestation.

Followed by Testing DNA of fetus by CHORIONIC VILLUS SAMPLING (CVS).   

Neural tube defects(NTDs) 

What is most common congenital malformation?

NTD - Neural Tube Defect

Is prevention of NTDs possible?

Yes.

Primary and secondary prevention is possible by peri conceptional folic acid therapy  

How to screen for NTDs?

  1. Ultrasound 
  2. Mid-Trimester Maternal Serum Alpha-Foetoprotein (MSAFP)   

ULTRASONOGRAPHIC (USG) EVALUATION 

at 16-20 wk gestation, 

especially if careful attention is paid to the 'lemon' and 'banana' signs which are good pointers to NTDs. 

DOWN SYNDROME

How common is Down syndrome?

Down syndrome is the most common cause of intellectual disability and accounts for about 15-30 per cent of cases. 

In India, the birth prevalence is reported to vary from one in 1230 to one in 1361.  

Is prenatal screening for Down syndrome accurate? 

Prenatal screening for Down syndrome started with maternal age as a screening tool and over the last two decades has evolved and achieved almost 99 per cent sensitivity.   

ARE SCREENING TESTS SAME FOR ALL PATIENTS?

The counselling should be non-directive and the caring physician should be supportive of the family's decision. 

However, it should be clarified that USG alone cannot rule out trisomy 21 or chromosomal disorders.  

KEY POINTS

Screening for carrier status for beta-thalassaemia and other haemoglobinopathies 

1.    Offered to all couples

2.   HB HPLC 

3.    At the preconception stage or in the first antenatal visit 

FOLIC ACID (0.4 mg per day daily) needs to be started in the preconception period FOR ALL WOMEN OF CHILD BEARING AGE for primary prevention of NTDs.   

The appropriate test for prenatal screening of Down syndrome for each patient would depend on the gestational age at consultation and the detection rate and error rate of the test. 

FIRST TRIMESTER 

First-trimester NT SCAN and DOUBLE-MARKER TESTING (combined screen) 

IMPORTANT FOR 

  1. Gestational age estimation 
  2. Identification of twin gestation & chorionicity 

SECOND TRIMESTER 

QUADRUPLE-MARKER TEST (at 16 wk gestation) 

USG evaluation at 16-20 wk 

  1. Foetal soft markers of aneuploidy 
  2. Foetal malformations  

AMNIOCENTESIS & FOETAL KARYOTYPING 

For pregnancies that screen positive for foetal aneuploidy

If invasive testing is being done for pregnancy, cytogenetic microarray testing can be offered after cost discussions.   

The role of NIPT for aneuploidies in routine screening is still debatable and its true cost-effectiveness needs to be calculated before its introduction in the screening programm.  

For all screening and diagnostic tests that are performed, accurate pre- and post-test genetic counselling in simple, easily understandable language is essential.