Non-invasive prenatal testing linked to decreased diagnostic testing

1. Fewer women were referred for genetic counseling and diagnostic testing after the introduction of non-invasive prenatal testing.

2. A third of abnormalities detected by chorionic villus sampling would not have been detected by non-invasive prenatal testing.

Evidence Rating Level: 2 (Good)           

Study Rundown: During pregnancy, women are offered genetic screening tests for chromosomal abnormalities and neural tube defects. In the event of a positive screening result, many women opt to undergo further diagnostic testing via amniocentesis or chorionic villus sampling (CVS). While informative, these tests pose a small risk of complications including rupture of membranes, infection and fetal injury or loss. More recently, non-invasive prenatal testing (NIPT) became available as an alternative secondary screening method; this method detects fetal genetic material in maternal serum and offers information about Trisomy risk without increasing risk of pregnancy loss and other morbidities associated with invasive diagnostic testing. Despite its benefits, NIPT can yield false positive or negative results. In the present work, authors determined whether rates of invasive diagnostic testing and referral for genetic counseling and were affected by the introduction of NIPT. They found that after NIPT was introduced, screening increased but fewer referrals for counseling and invasive diagnostic testing were performed.

Strengths of the study included large sample size and prospective data collection. However, the retrospective design is associated with inherent selection bias, limiting generalizability. Additionally, the authors were only able to report absolute numbers of patients referred to their center. Additional studies in larger healthcare networks are merited to better determine whether at-risk women are being appropriately referred for counseling and invasive testing.

Click to read the study in AJOG

Relevant Reading: Overview of the impact of noninvasive prenatal testing on diagnostic procedures

In-Depth [retrospective cohort]: This study characterized referral for counseling and testing before (n=3944) and after (n=2824) NIPT was used in clinical practice. The main outcomes of interest were the number of women referred for genetic counseling and invasive diagnostic testing during the pre-NIPT and post-NIPT periods, and the number of non-NIPT candidates who were referred for counseling and prenatal diagnosis.

There was a 28.4% decrease in referrals for genetic counseling and invasive diagnostic testing (p=0.001), even for women who were non-candidates for NIPT (p=0.043). More women underwent first or second trimester screening after NIPT was introduced (p<0.001), but more women declined diagnostic testing during the post-NIPT period (p=0.001). Among women who underwent CVS and had an abnormal result, 32.4% had an abnormality not detectable by NIPT.

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