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Screening Process
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The prenatal screening includes an ultrasound and a blood draw. The blood sample is used to measure the concentration of two proteins, PAPP-A (pregnancy associated plasma protein A), and free ß-hCG (free-beta human chorionic gonadotropin) for first trimester screening, and AFP, free hCGß, uE3 and inhibin-A for second trimester screening. These proteins (also known as maternal serum markers) are released into the maternal blood in every pregnancy, and are associated with a clearly elevated or reduced concentration in maternal serum when the fetus is affected by an anomaly.
The ultrasound looks for the presence of the fetal nasal bone and measures the nuchal translucency. The nuchal translucency is a fluid filled area at the back of the fetal neck, present in every pregnancy. These combined biochemical (blood) and biophysical (ultrasound) markers yield the most sensitive screening results possible at the earliest point during the pregnancy.
Screening options available for trisomies and neural tube defects
FIRST TRIMESTER SCREENING
Screening options
Time of screen and bio-markers
Combined biochemistry
NT at 11 – 13 weeks + 6 days, free HCG & PAPP-A at 11- 13 weeks + 6 days
SECOND TRIMESTER SCREENING
Screening options
Time of screen and bio-markers
Triple test
AFP, hCG (or free hCG) and uE3 at 14-20 weeks
Quadruple test
AFP, hCG (or free hCG), uE3 and inhibin-A at 14-20 weeks
First Trimester screening
Combined Biochemistry
The first trimester combined biochemistry test yields the most reliable risk assessment as the results are based on age of the patient, nuchal translucency measurement and biochemistry analysis of blood sample. The combined biochemistry test has 91% detection rate for Down syndrome and a 5% false positive rate; and a 95% detection rate for trisomy 18 and trisomy 13 at a 0.3% false positive rate.
Biochemistry only
In cases where it is not possible to have the ultrasound for nuchal translucency done, biochemistry alone is opted for to assess the risk of aneuploidies which gives 65% – 70 % detection rate.
Second trimester screening
The triple or quadruple screen is a test in the second trimester of pregnancy and is usually ordered between the 14th and 20 weeks. These tests have been established as a triple or quad screen because they involve measurement of 3 substances or biomarkers -AFP, free ß hCG and unconjugated estriol for triple test and 4 biomarkers such as – AFP, free ß hCG, unconjugated estriol and inhibin A for quadruple screen.
Triple marker gives a detection rate of about 60 – 65% while the quadruple markers give 67-71% detection rate.
Technology
To provide the best possible services in maternal health during pregnancies we have adopted comprehensive state-of-art technologies that ensure accuracy, speed, reliability and affordability.
- Dissociation Enhanced Lanthanide Fluorescent Immunoassay (DELFIA) – a method that employs Time Resolved Flourimetry (TRF) and provides an optimal tool for bio-affinity assays with excellent sensitivity (10x), dynamic range, stability, and flexibility and is recommended by Fetal Medicine Foundation (FMF) UK.
- LifeCycle™ is dedicated screening management software with clinically validated risk calculation with versatile functionality. The screening management software provides independent risk calculation engine, suitable for both 1st and 2nd trimester screening. Because the system has been fully validated and all calculation methods, algorithms and values are supported by current published literature, LifeCycle provides full confidence in maternal risk assessment programs.
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