Abstract
BackgroundDifferent strategies have been designed for clinical implementation of cell-free DNA (cfDNA) testing. We aimed to evaluate the performance of a contingent strategy based on conventional screening and offering cfDNA to the intermediate-risk group, for the screening for trisomies 21, 18 and 13. Secondary objectives were to assess the uptake of cfDNA in women with intermediate-risk, to evaluate the performance of cfDNA testing, and the preferences of pregnant women with intermediate risk.MethodsProspective observational pilot study between February 2016 and March 2017. Singleton pregnancies with a known outcome were included in the study. At the conventional screening (first trimester combined test or second trimester quadruple test) women were classified in high (risk ≥1:250) or low risk (< 1:250). For the study, a contingent strategy was applied: following the conventional screening women were classified into three groups: high risk (risk ≥1:10 or nuchal translucency ≥3 mm), intermediate-risk (risk 1:11 to 1:1500) and low risk (< 1:1500), and a cfDNA test was offered to those at the intermediate risk.ResultsFor the analysis, 2639 women were included, 2422 (91.8%) had a first trimester combined test and 217 (8.2%) a second trimester quadruple test. There were 5 cases of trisomy 21, 4 of trisomy 18 and none of trisomy 13. For the contingent strategy, the detection rate and false positive rates were 88.9% (8/9) and 1.3% (35/2630), respectively. For the conventional strategy, the detection rate and false positive rates were 66.7% (6/9) and 5.3% (140/2630), respectively. The cfDNA test had a detection rate for trisomy 21 of 100% (3 out of 3), and a false positive rate of 0.2% (1/466). In a survey, 81.8% (374/457) of women in the intermediate-risk group would choose cfDNA testing as the second line test, mainly due to the lack of risk for the fetus.ConclusionA contingent screening strategy for trisomies 21, 18 and 13, based on conventional screening, and offering a cfDNA test to women with a risk between 1:11 to 1:1500, reduced the false positive rate and increased the detection rate for these trisomies. Moreover, this strategy is well accepted by women.
Highlights
Different strategies have been designed for clinical implementation of cell-free DNA testing
Study design and population This was a prospective observational study performed between February 2016 and March 2017 at Vall d’Hebron University Hospital, Barcelona, Spain. This was a pilot study, previous to the implementation of a contingent strategy based on conventional screening and offering cell-free DNA (cfDNA) to the intermediate-risk group at the public health system in our region, The study population was women referred consecutively to the hospital for aneuploidies screening
Study population Two thousand nine hundred and eighty-six patients were screened in this period, 2706 women were eligible for the study, from these 67 (2.5%) were excluded, 2639 women were included for analysis, 2422 (91.8%) who had a first trimester combined test and 217 (8.2%) a second trimester quadruple test (Fig. 3)
Summary
Different strategies have been designed for clinical implementation of cell-free DNA (cfDNA) testing. We aimed to evaluate the performance of a contingent strategy based on conventional screening and offering cfDNA to the intermediate-risk group, for the screening for trisomies 21, 18 and 13. The study of cell-free DNA (cfDNA) in maternal blood has shown higher detection rates [2, 3], with an important reduction in false positive rates, minimizing the number of invasive procedures and their complications. An alternative is a contingent strategy in two steps; firstly a conventional screening is performed, and secondly, a cfDNA test is offered only to those patients with intermediate-risk. This strategy would increase the detection rate and reduce the false positive rate [4]. Secondary objectives were to assess the uptake of cfDNA in women with intermediate-risk, to evaluate the performance of cfDNA testing, and the preferences of pregnant women with intermediate risk
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