Sorted By Test Name - Mayo Medical Laboratories

POC
8887
CVS
80257
An interpretative report will be provided.
Clinical References: Van Dyke DL, Roberson JR, Wiktor A: Chapter 31: Prenatal cytogenetic
diagnosis. In Clinical Laboratory Medicine. Edited by KD McClatchey. Second edition, Philadelphia,
Lippincott, Williams & Wilkins, 2002, pp 636-657
Chromosome Analysis, Autopsy, Products of Conception, or
Stillbirth
Clinical Information: Chromosomal abnormalities may result in malformed fetuses, spontaneous
abortions, or neonatal deaths. Estimates of the frequency of chromosome abnormalities in spontaneous
abortuses range from 15% to 60%. Chromosome studies of products of conception (POC) may provide
useful information concerning the cause of miscarriage and, thus, the recurrence risk for pregnancy loss
and risk for having subsequent children with chromosome anomalies. Chromosome analysis of the
stillborn infant or neonate (autopsy) may be desirable, particularly if there is a family history of 2 or more
miscarriages or when malformations are evident. For neonatal cases, peripheral blood is the preferred
specimen for chromosome analysis (CMS/8696 Chromosome Analysis, for Congenital Disorders, Blood).
Useful For: Autopsy: -Second-tier testing for chromosomal abnormalities -Follow-up testing when
chromosomal analysis and other studies on peripheral blood are inconclusive or when peripheral blood
quality is poor or sampling is not possible Products of Conception or Stillbirth: -Diagnosing chromosomal
causes for fetal death -Determining recurrence risk for future pregnancy losses
Interpretation: The finding of a chromosome abnormality may explain the cause of a miscarriage or
stillbirth, particularly when the chromosome results show aneuploidy or an unbalanced structural
rearrangement. Some of the chromosome abnormalities that are detected in these specimens are balanced
(no apparent gain or loss of genetic material) and may not be associated with birth defects, miscarriage, or
stillbirth. For balanced chromosome rearrangements, it is sometimes difficult to determine whether the
chromosome abnormality is the direct cause of a miscarriage or stillbirth. In these situations, chromosome
studies of the parents' peripheral blood may be useful to determine if an abnormality is familial or de
novo. De novo, balanced rearrangements can cause miscarriages or stillbirth by producing submicroscopic
deletions, duplications, or gene mutations at the site of chromosome breakage. A normal karyotype does
not rule out the possibility of birth defects, such as those caused by submicroscopic cytogenetic
abnormalities, molecular mutations, and environmental factors (ie, teratogen exposure). Due to bacterial
contamination or nonviable cells, we are unable to establish a viable culture 20% of the time. In these
cases, the specimen cannot be used for chromosome analysis, so the FISH aneuploidy test is automatically
initiated. While the FISH test is not as comprehensive as a chromosome analysis, it can provide
information with regard to many of the most common numeric abnormalities in spontaneous miscarriage
and stillbirth.
Reference Values:
46,XX or 46,XY. No apparent chromosome abnormality.
An interpretive report will be provided.
Clinical References: Dewald GW, Michels VV: Recurrent miscarriages: cytogenetic causes and
genetic counseling of affected families. Clin Obstet Gynecol 1986;29:865-885
Chromosome Analysis, Chorionic Villus Sampling
Clinical Information: Although not used as widely as amniocentesis, the use of chorionic villus
sampling (CVS) for chromosome analysis is an important procedure for the prenatal diagnosis of
chromosome abnormalities. CVS can be collected by either transcervical or transabdominal techniques. It
can be safely performed at an earlier gestational age (ie, 9-12 weeks) than amniocentesis (usually
performed between 15-18 weeks of gestation). The medical indications for performing chromosome
studies on CVS are similar to amniocentesis, and may include advanced maternal age, abnormal first
trimester screen, history of a previous child with congenital anomalies, abnormal fetal ultrasound, and
family history of a chromosome abnormality.
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