Test ID: CVS
Chromosome Analysis, Chorionic Villus Sampling
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Prenatal diagnosis of chromosome abnormalities (trisomies, deletions, translocations, etc) at about 9 to 12 weeks of gestation
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
Includes 2 banded karyograms, analysis of 20 or more metaphases, and other techniques when required.
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Chorionic Villus Sampling, Chromosomes
CVS
Down Syndrome
Karyotype, Chorionic Villus Sampling
Trisomy 21
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Provide a reason for referral with each specimen. The laboratory will not reject testing if this information is not provided, but appropriate testing and interpretation may be compromised or delayed.
Container/Tube: 15-mL tube containing 15-mL of transport media
Specimen Volume: 20-30 mg
Collection Instructions:
1. Collect chorionic villus specimen (CVS) by the transabdominal or transcervical method.
2. Transfer the CVS to a Petri dish containing transport medium.
3. Using a stereomicroscope and sterile forceps, assess the quality and quantity of the villi and remove any blood clots and maternal decidua.
Additional Information: Advise Express Mail or equivalent if not on courier service.
Forms:
1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
2. If not ordering electronically, submit a Cytogenetics/AFP Congenital Disorders Request Form (Supply T238) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Tissue | Refrigerated (preferred) | |
| Ambient | ||
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
46,XX or 46,XY. No apparent chromosome abnormality.
An interpretive report will be provided.
Interpretation Provides information to assist in interpretation of the test results
Cytogenetic studies on chorionic villus sampling (CVS) are considered more than 99% reliable for the detection of most fetal chromosome abnormalities. However, subtle or cryptic abnormalities involving microdeletions usually can be detected only with the use of targeted FISH testing.
Approximately 3% of chorionic villi specimens analyzed are found to have chromosome abnormalities. Some of these chromosome abnormalities are balanced and may not be associated with birth defects. 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). For these reasons, clinicians should inform their patients of the technical limitations of chromosome analysis before the procedure is performed, so that patients may make an informed decision about pursuing the procedure.
It is recommended that a qualified professional in Medical Genetics communicate all results to the patient.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Interfering factors
Technical:
-Inadequate amount of specimen (we recommend 20-30 mg of chorionic villus sampling [CVS]) may not permit adequate analysis
-Exposure of the specimen to temperature extremes may kill cells and severely interfere with attempts to culture cells
-Improper packaging may result in broken, leaky, and contaminated specimens during transport
-Extended transport time
Biological:
-Contamination of the CVS by maternal cells can cause minor interpretive problems
-False chromosome mosaicism may occur due to artifact of culture.
-True mosaicism may be missed due to statistical sampling error
-Presence of chromosome abnormalities in placental cells that do not occur in cells of the fetus (confined placental mosaicism)
-Subtle structural chromosome abnormalities can occasionally be missed
This test should be performed for prenatal diagnostic purposes only. Chromosome analysis on CVS collected from products of conception (ie, stillbirth or miscarriage tissue) should be ordered as POC/8887 Chromosome Analysis, Autopsy, Products of Conception, Stillbirth.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Van Dyke DL, Roberson JR, Wiktor A: Prenatal cytogenetic diagnosis. In KD McClatchey's Clinical Laboratory Medicine. 2nd Edition. Philadelphia, Lippincott, Williams, & Wilkins, 2002, Chapter 31, pp 636-657
Method Description Describes how the test is performed and provides a method-specific reference
The chorionic villi is thoroughly cleaned using sterile forceps to remove remaining maternal decidua and blood clots. The villi are then treated with trypsin and collagenase. The cells are grown culture media for 5 to 10 days. In the harvest procedure, the cells are exposed to colcemid and hypotonic solution, then fixed with glacial acetic acid and methanol. Metaphase cells are dropped onto microscope slide and are routinely stained by G-banding, but other staining methods are frequently employed as needed. Twenty metaphases from 3 or more primary cultures are examined. In cases of pseudomosaicism or when true mosaicism is suspected, up to 6 different primary cultures are analyzed. Five or more metaphases are stored in a computer-based imaging system and karyograms are made from 2 or more representative metaphases. (Breed AS, Mantingh A, Beekhuis JR, et al: The predictive value of cytogenetic diagnosis after CVS: 1,500 cases. Prenat Diagn 1990;10:101-110; Canadian Collaborative CVS-Amniocentesis Clinical Trial Group: Multicentre randomized clinical trial of chorionic villus sampling and amniocentesis. Lancet 1989;1:1-6; Ledbetter DH, Martin AO, Verlinsky Y, et al: Cytogenetic results of chorionic villus sampling: high success rate and diagnostic accuracy in the United States collaborative study. Am J Obstet Gynecol 1990;162:495-501; Spurbeck JL, Carlson RO, Allen JE, Dewald GW: Culturing and robotic harvesting of bone marrow, lymph nodes, peripheral blood, fibroblasts, and solid tumors with in situ techniques. Cancer Genet Cytogenet 1988;32:59-66)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Samples processed Monday through Sunday. Results reported Monday through Friday, 8 a.m.-5 p.m. CST.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
88235-Tissue Culture; amniotic fluid or chorionic villus cells
88291-Interpretation and report
88299-Unlisted cytogenetic study (Refer to patient report to apply the appropriate CPT code below in place of this unlisted cytogenetic study CPT code)
Based on the total number of cells analyzed and counted, MML would recommend the following:
Chromosome analysis count 15 cells, karyotypes with banding; CPT Codes 88267, 88280
Chromosome analysis with less than 15 cells, karyotypes with banding; CPT Codes 88267 w/ modifier 52, 88280
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 16143 | Specimen | 31208-2 |
| 16335 | Specimen ID | N/A |
| 16790 | Source | N/A |
| 16144 | Order Date | N/A |
| G_737 | Reason For Referral | 42349-1 |
| 16148 | Method | In Process |
| 50465 | Banding Methods | 62359-5 |
| 16150 | Results | 35129-6 |
| 16151 | Interpretation | 69965-2 |
| 16152 | Amendment | In Process |
| 16153 | Consultant | N/A |
| 16154 | Report Date | N/A |
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