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CMECNE

What Is the Best Follow-Up Diagnostic Test After a High-Risk NIPT Result?

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Learning Objectives and CME/Disclosure Information

This activity is intended for healthcare providers delivering care to women and their families.

After completing this activity, the participant should be better able to:

1. Contrast the differences between placental and fetal tissues in relation to cytogenetic differences
2. Choose the preferable confirmatory test following a positive noninvasive prenatal screening test

Estimated time to complete activity: 0.25 hours

Faculty:

Susan J. Gross, MD, FRCSC, FACOG, FACMG
President and CEO, The ObG Project

Disclosure of Conflicts of Interest

Postgraduate Institute for Medicine (PIM) requires instructors, planners, managers and other individuals who are in a position to control the content of this activity to disclose any real or apparent conflict of interest (COI) they may have as related to the content of this activity. All identified COI are thoroughly vetted and resolved according to PIM policy. PIM is committed to providing its learners with high quality CME activities and related materials that promote improvements or quality in healthcare and not a specific proprietary business interest of a commercial interest.

Faculty: Susan J. Gross, MD, receives consulting fees from Cradle Genomics, and has financial interest in The ObG Project, Inc.

Planners and Managers: The PIM planners and managers, Trace Hutchison, PharmD, Samantha Mattiucci, PharmD, CHCP, Judi Smelker-Mitchek, MBA, MSN, RN, and Jan Schultz, MSN, RN, CHCP have nothing to disclose.

Method of Participation and Request for Credit

Fees for participating and receiving CME credit for this activity are as posted on The ObG Project website. During the period from Dec 31 2017 through Dec 31 2021, participants must read the learning objectives and faculty disclosures and study the educational activity.

If you wish to receive acknowledgment for completing this activity, please complete the post-test and evaluation. Upon registering and successfully completing the post-test with a score of 100% and the activity evaluation, your certificate will be made available immediately.

For Pharmacists: Upon successfully completing the post-test with a score of 100% and the activity evaluation form, transcript information will be sent to the NABP CPE Monitor Service within 4 weeks.

Joint Accreditation Statement

In support of improving patient care, this activity has been planned and implemented by the Postgraduate Institute for Medicine and The ObG Project. Postgraduate Institute for Medicine is jointly accredited by the Accreditation Council for Continuing Medical Education (ACCME), the Accreditation Council for Pharmacy Education (ACPE), and the American Nurses Credentialing Center (ANCC), to provide continuing education for the healthcare team.

Physician Continuing Medical Education

Postgraduate Institute for Medicine designates this enduring material for a maximum of 0.25 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Continuing Nursing Education

The maximum number of hours awarded for this Continuing Nursing Education activity is 0.2 contact hours.

Read Disclaimer & Fine Print

BACKGROUND AND PURPOSE:

  • DNA that circulates in the maternal compartment is mostly derived from placenta (cytotrophoblast layer) and not the fetus
  • Fetal and placental cells both originate from the fertilized oocyte, but diverge early in pregnancy into distinct tissues
    • Placenta can tolerate different cell lines (mosaicism) and may not perfectly match the fetal chromosomal complement, resulting in false positive and negative NIPS results
  • There are other causes that may result in false positive and negative NIPS reports, such as vanishing twin or maternal chromosomal anomalies
  • Therefore, there is universal agreement that a positive cfDNA report requires confirmation based on invasive testing with either CVS or amniocentesis
  • Grati et al. (Prenatal Diagnosis, 2015) used an extensive database to determine how often placental DNA (CVS results) matched fetal DNA (amniocentesis results), broken out by chromosome and cellular layer, to determine whether amniocentesis and/or CVS is the more appropriate confirmatory test.

METHODS:

  • Data on 52,673 karyotypes were analyzed to determine frequency of mosaicism involving cytophoblasts, for trisomies 21 (T21), 18 (T18), 13 (T13) and monsomy X (MX)
  • Karyotypes were obtained from cytorophoblast (outer layer, DNA source for NIPS), mesenchyme and confirmatory amniocentesis

RESULTS:

Using cytotrophoblast karyotype as a proxy for NIPS, authors posited the following

  • After a high-risk NIPS result, mosaicism on confirmatory CVS requiring a follow up amniocentesis would be:
    • 2% in T21
    • 4% in T18
    • 22% in T13
    • 59% in MX
  • When mosaicism is detected by CVS, the likelihood of fetal confirmation by amniocentesis would be:
    • 44% in T21
    • 14% in T18
    • 4% in T13
    • 26% in MX

CONCLUSION:

  • For T21/18, confirmatory CVS may still be an option, especially if there is a clinical indication to obtain early results
    • Small but still real risk for inconclusive results
  • For MX/T13, amniocentesis seems most appropriate for follow-up after high risk cfDNA result due to high likelihood of a mosaic result on confirmatory CVS
  • The authors state “If an ultrasound anomaly suggesting the suspected karyotype anomaly is found, CVS could be offered to the patient regardless of risk of need for a secondary procedure because an early diagnosis may be preferable.”

Learn More – Primary Sources:

The type of feto-placental aneuploidy detected by cfDNA testing may influence the choice of confirmatory diagnostic procedure

Diagnostic cytogenetic testing following positive noninvasive prenatal screening results: a clinical laboratory practice resource of the American College of Medical Genetics and Genomics (ACMG)

Take a post-test and get CME credits

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Related ObG Topics:

Practical info on evidence based medicine for your women's healthcare practice
cfDNA vs. Routine Screening – How Do They Compare?
Does cfDNA in First Trimester Signal Subsequent Preeclampsia?
NIPS vs. Microarray for Pathogenic Results
Should Amniocentesis or Chorionic Villus Sampling Be Offered to All Pregnant Women?
How Accurate is NIPT as a Screening Test for Chromosomal Aneuploidies?

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Computer System Requirements

OBG Project CME requires a modern web browser (Internet Explorer 10+, Mozilla Firefox, Apple Safari, Google Chrome, Microsoft Edge). Certain educational activities may require additional software to view multimedia, presentation, or printable versions of their content. These activities will be marked as such and will provide links to the required software. That software may be: Adobe Flash, Apple QuickTime, Adobe Acrobat, Microsoft PowerPoint, Windows Media Player, or Real Networks Real One Player.

Disclosure of Unlabeled Use

This educational activity may contain discussion of published and/or investigational uses of agents that are not indicated by the FDA. The planners of this activity do not recommend the use of any agent outside of the labeled indications.

The opinions expressed in the educational activity are those of the faculty and do not necessarily represent the views of the planners. Please refer to the official prescribing information for each product for discussion of approved indications, contraindications, and warnings.

Disclaimer

Participants have an implied responsibility to use the newly acquired information to enhance patient outcomes and their own professional development. The information
presented in this activity is not meant to serve as a guideline for patient management. Any procedures, medications, or other courses of diagnosis or treatment discussed or suggested in this activity should not be used by clinicians without evaluation of their patient’s conditions and possible contraindications and/or dangers in use, review of any applicable manufacturer’s product information, and comparison with recommendations of other authorities.

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