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March 5, 2014
DynaMed EBM Journal Volume 9, Issue 10
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Credits
Physicians: .25 AMA PRA Category ICreditsTM
Family Physicians: .25 Prescribed credits
Nurse Practitioners: .25 Contact hours
Release Date: March 5, 2014
Expiration Date: March 5, 2015
Estimated Completion Time: 15 minutes
There is no fee for this activity.
To Receive Credit
In order to receive your certificate of participation, you should read the information about this activity, including the disclosure statements, review the entire activity, take the post-test, and complete the evaluation form. You may then follow the directions to print your certificate of participation. To begin, click the CME icon at the end of the article.
Program Overview
Learning Objectives
Upon successful completion of this educational program, the reader should be able to:
1. Discuss the significance of this article as it relates to your clinical practice.
2. Be able to apply this knowledge to your patient's diagnosis, treatment and management.
Faculty Information
Alan Ehrlich, MD - Assistant Clinical Professor in Family Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA; Senior Deputy Editor, DynaMed, Ipswich, Massachusetts, USA
Michael Fleming, MD, FAAFP - Assistant Clinical Professor of Family Medicine and Comprehensive Care, LSU Health Science Center School of Medicine, Shreveport, Louisiana, USA; Assistant Clinical Professor of Family Medicine, Department of Family and Community Medicine, Tulane University Medical School, New Orleans, Louisiana, USA; Chief Medical Officer, Amedisys, Inc. & Antidote Education Company
Disclosures
Dr. Ehrlich, Dr. Fleming, DynaMed Editorial Team members, and the staff of Antidote Education Company have disclosed that they have no relevant financial relationships or conflicts of interest with commercial interests related directly or indirectly to this educational activity.
No commercial support has been received for this activity.
Accreditation Statements
ACCME: This activity has been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education through the joint sponsorship of Antidote EducationCompany and EBSCO Publishing. Antidote is accredited by the ACCME to provide continuing medical education for physicians. Antidote Education Company designates this enduring activity for a maximum of 0.25 AMA PRA Category 1 CreditsTM. Physicians should only claim credit commensurate with the extent of their participation in the activity.
AAFP: Enduring Material activity, DynaMed EBM Focus, has been reviewed and is acceptable for up to 13 Prescribed credits by the American Academy of Family Physicians. AAFP certification begins March 7, 2012. Term of approval is for one year from this date with the option of yearly renewal. Each EBM Focus is worth .25 Prescribed credits. Physicians should claim only the credit commensurate with the extent of their participation in the activity.
AANP: This program is approved for 0.25 contact hour of continuing education by the American Academy of Nurse Practitioners.
Program ID: 1304159R
Last week 525 journal articles were evaluated via DynaMed's Systematic Literature Surveillance and summaries of 220 articles were added to DynaMed content.
Based on criteria for selecting "articles most likely to change clinical practice," one article was selected by the DynaMed Editorial Team.
Maternal Plasma DNA Screening for Fetal Trisomies 21 and 18 May Reduce the Need for Invasive Follow-up Testing Compared to Standard Aneuploidy Screening
Reference: N Engl J Med 2014 Feb 27;370(9):799 (level 2 [mid-level] evidence)
Screening for chromosomal abnormalities is now part of standard prenatal care, and the American College of Obstetricians and Gynecologists currently recommends screening unselected women with both nuchal translucency and biochemical markers (Obstet Gynecol 2007 Jan;109(1):217). Advances in rapid DNA sequencing and sequence analysis have led to the development of new technologies for prenatal screening, including screening for chromosomal abnormalities such as trisomy 21 (Down syndrome) and trisomy 18 (Edward syndrome). Cell-free DNA testing using massively parallel sequencing of maternal plasma has recently been shown to have high predictive performance for detection of fetal trisomy in study populations involving karyotypes associated with very high risk of aneuploidy (Genet Med 2011 Nov;13(11):913, Obstet Gynecol 2012 May;119(5):890). Now, a validation cohort study evaluates the prognostic performance of massively parallel sequencing cell-free DNA testing and standard aneuploidy screening for fetal trisomies in a general obstetric population.
A total of 2,042 adult women (mean age 30 years) with singleton pregnancies of gestational age ≥ 8 weeks had cell-free DNA testing and standard aneuploidy screening for detection of fetal trisomies 21, 18, and 13. Cell-free DNA testing consisted of massively parallel sequencing of maternal plasma cell-free DNA from 10-mL sample of peripheral venous blood taken during the first, second, or third trimester. Standard aneuploidy screening included assays for first or second trimester serum markers, either with or without nuchal translucency measurement from fetal ultrasound. The reference standard was newborn physical exam, or karyotype analysis in the case of nonlive birth. Overall, 1,914 women without loss to follow-up and having results for karyotype analysis, cell-free DNA testing, and standard aneuploidy screening were included in the analysis.
There were a total of 5 cases (0.3%) of trisomy 21 and 2 cases (0.1%) of trisomy 18 by reference standard. For detection of trisomy 21, cell-free DNA testing had sensitivity 100%, specificity 99.7%, positive predictive value 45.5%, and negative predictive value 100%. The corresponding performance measures for standard aneuploidy screening were sensitivity 100%, specificity 96.4%, positive predictive value 4.2%, and negative predictive value 100%. Similarly, for detection of trisomy 18, cell-free DNA testing had sensitivity 100%, specificity 99.8%, positive predictive value 40%, and negative predictive value 100%. The corresponding performance measures for standard aneuploidy screening were sensitivity 100%, specificity 99.4%, positive predictive value 8.3%, and negative predictive value 100%. For both trisomy 21 and trisomy 18, cell-free DNA testing was associated with significantly increased specificity and positive predictive value compared to standard aneuploidy screening.
The results of this study confirm that a negative result with cell-free DNA testing using massively parallel sequencing of maternal plasma is associated with a greatly reduced risk of fetal trisomy 21 and trisomy 18 in a general obstetric population. The positive predictive values for detecting each fetal trisomy were low for both cell-free DNA testing and standard aneuploidy screening, highlighting the need for more invasive confirmatory testing (such as amniocentesis) for diagnosing these conditions in the case of a positive result. However, cell-free DNA testing was associated with significantly higher specificity and positive predictive values for both fetal trisomies, meaning that fewer women would be needlessly discomforted by a false positive result, and fewer would require invasive testing for confirmation.
For more information see the Screening and monitoring during pregnancy, Down syndrome, and Trisomy 18 topics in Dynamed.
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