A full-area population screening for chromosomal aberrations – the serum integrated test has been implemented in the South Bohemian region since 2007. The test is available to all 8,000 pregnant women in our region only in the screening centre Centre for Medical Genetics Ltd. – OKB EUC Klinika České Budějovice s.r.o.
If a patient so wish, we can accompany the test by the NT measured by an accredited sonographer and perform a sequential integrated test.
Due to the possibility of performing a number of screening tests, it is advisable to brief the patient in detail on all screening options
I. The serum integrated test in the first and second trimester consists of collecting two blood samples for biochemical testing:
- Blood sample for PaPP-A in the first trimester – the most effective blood samples are collected between weeks 10+0 and 11+3 according to the ultrasound scan
- Blood sample for AFP, hCG, uE3 in the second trimester – from week 14+0 – from week 14+0 integration in the Centre for Medical Genetics Ltd.
the result of the test is obtained by an integration of both steps and will be released by the screening centre only after the sample from the second trimester is examined.
The low PaPP-A level selects the group of patients with the highest risk who can be examined already in the first trimester and the pathology can be detected including chorionic villus sampling (CVS) already in the first trimester.
if a patient comes later or if the first step (a blood sample for PaPP-A testing) is not done, it doesn’t matter – there will be the usual blood sample collected for AFP, hCG, uE3 testing in the second trimester from 14+0
The false-positive rate of the serum integrated test is 4.5 – 5%.
II. Sequential integrated test in the first and second trimester
In selected cases, we perform the sequential integrated test (combined test in the first trimester + biochemical testing in the second trimester) including the addition of the NT (nuchal translucency) measured by an accredited sonographer in our centre. These tests are added to the test if the patient wishes so (for a fee) or due to a medical indication (in this case, the patient has a request from her gynaecologist).
According to the Recommended Procedure No. 1 of the Society of Medical Genetics and Genomics of the Czech Medical Society of J. E. Purkyne effective
from 15 January 2014: “Performance of general prenatal screening for congenital defects”, the sequential integrated test has the highest detection rate and the lowest false-positive rate – improved FPR (false-positive rate) / DR (detection rate) ratio than the first-trimester test. A higher detection rate of the sequential integrated test against the combined test in the first trimester has been many years part of the Recommendation on the Screening for Fetal Chromosomal Aberrations of the American College of Obstetricians and Gynecologists (ACOG). Also according to the latest Recommendation of the ACOG in May 2016, the integrated test has a higher detection rate than the combined first-trimester test.
In the case of a complete integrated test (including accredited NT), the detection rate is 95% at 3% false-positive rate.
Sequential integrated test:
- 1st blood sample collection in the first trimester (collecting blood samples for biochemical testing)
from week 10+0 to 11+3 - week 11 to 13+6: ultrasound examination of the fetus including NT (nuchal translucency) scan by an accredited sonographer at the FMF London
- 2nd blood sample collection in the second trimester (AFP, hCG, uE3) – from week 14+0 integration at the Centre for Medical Genetics Ltd.
Evaluation of the first part of the integrated test at our centre in the first trimester
In case of positive rate at a risk of 1:100, it is possible to perform invasive testing (chorionic villus sampling ), at a risk from 1:100 to 1:350, it is possible to perform non-invasive prenatal test (NIPT). All patients with a negative first-trimester part of the integrated test are recommended for blood testing in the second trimester from week 14+0 for HCG, AFP, E3.
TEST RESULT
The result of our serum integrated and sequential integrated test is available in the same stage of pregnancy as the result of the first-trimester test.
Benefits of the first- and second-trimester serum integrated and sequential integrated test:
- The most effective method of conventional screening for Down syndrome applicable to the whole population
- detection rate is higher than the one of the first-trimester test (see our contribution to the publication: Drahomir Springera, Jaroslav Loucky, Pavel Tesner, David Cutka, David Stejskal, Vladimir Gregor and Tomas Zima, Importance of the integrated test in the Down’s syndrome screening algorithm. J Med Screen 2018 Jan 01.:969141317752533.)
- speeds up the diagnosis – based on low PaPP-A, it detects a part of pathologies in the whole population as early as in the first trimester
- a large part of birth defects is detected as early as in the first trimester at the Centre for Medical Genetics Ltd.
- another significant part is then detected in week 20 of pregnancy as part of the detailed genetic ultrasound scan including examination of the fetal heart that can be performed for direct payment by a patient at our centre
- the test detects spina bifida already in week 16 of pregnancy (unlike the first-trimester test, which does not detect spina bifida)
- the test with a higher AFP indicates possible pregnancy complications in the third trimester
- this is the so-called population test (as opposed to selected patients for the first-trimester test)
- safe invasive method – amniocentesis (at highly professional centres, the risk of miscarriage after amniocentesis is not statistically higher compared to other pregnancies)
More than 84,000 serum integrated or sequential integrated tests (about 97% of pregnant women of the South Bohemian region and part of the Vysocina Region) have so far been performed over a period of 11 years. The integrated test detected 177 of the 187 cases of Down syndrome, which corresponds to the detection rate of 95%!!
- The integrated test was negative in 1.5 cases per 10,000 live-borns
(detection rate 95%).
- Only the first-trimester test is negative in 4-5 cases per 10,000 live-borns (detection rate 83%)!!