June 2018 — Molecular Diagnostics 2

A 32-year-old female presented to OB/GYN at 18 weeks gestation. Mutliple ultrasound anomalies were detected, including postaxial polydactyly, choroid plexus cysts, and omphalocele. Non-invasive prenatal screening (NIPS) via cell-free DNA sequencing was ordered to screen for the presence of common trisomies (13, 18, 21). NIPS revealed a borderline positive result for chromosome 18 (segmentation plot shown below). A prenatal chromosomal microarray was ordered to confirm the screening result, and the results for chromosome 18 are shown:

1. Segmentation plot of chromosome 18. The purple dashed line indicates copy number in a normal sample, the green dashed line is the average copy state for the entire chromosome in this sample, and the red line represents the copy state for binned regions along the chromosome (with the black dots representing individual bins).
2. Chromosomal Microarray plot showing chromosome 18: Copy number segment call in blue, Weighted Log2 Ratio of individual probes, and Smooth Signal indicating copy state along the chromosome.
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Ross Rowsey, Ph.D.
Fellow, Clinical Molecular Genetics
Mayo Clinic
Hutton Kearney, Ph.D
Consultant, Laboratory Medicine and Pathology
Mayo Clinic
Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine

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This post was developed by our Education and Technical Publications Team.