Test Overview
Test Methodology

Fluorescence In Situ Hybridization (FISH)

Test Usage

Screening for chromosomal aneuploidies of chromosomes 13, 18, 21, X, and Y in prenatal specimens

Reference Range *

Interpretive report provided

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

This test does not detect aneuploidy of chromosomes other than 13, 18, 21, X, or Y. This test does not detect other chromosomal or structural anomalies.
Low levels of mosaicism involving chromosomes 13, 18, 21, X, or Y may not be detected by this procedure.

Test Details
Days Set Up
Monday - Friday
Analytic Time

4 - 5 days

Soft Order Code
Reference Laboratory
Special Testing
Specimen Requirements
Collection Instructions

Amniotic fluid:
1. Optimal timing for specimen collection is during 14 to 18 weeks of gestation, but specimens collected at other weeks of gestation are also accepted. Provide gestational age at the time of amniocentesis.
2. Discard the first 2 mL of amniotic fluid.
1. Collect specimen by the transabdominal or transcervical method.
2. Transfer chorionic villi to a Petri dish containing transport medium (Such as CVS Media (RPMI) and Small Dish
3. Using a stereomicroscope and sterile forceps, assess the quality and quantity of the villi and remove any blood clots and maternal decidua.
4. Transfer to a sterile screw capped tube
Send to Specimen Processing refrigerated

Special Handling

Provide a reason for referral and gestational age with each specimen, and verify the specimen source. The laboratory will not reject testing if this information is not provided, but appropriate testing and interpretation may be compromised or delayed.

Normal Volume
20-25 mL Amniotic fluid OR 20-30 mg CVS in 15 mL RPMI
Minimum Volume
2 mL amniotic fluid; CVS 2 mg in 15 mL of RPMI
Storage Temperature
Refrigerated preferred, ambient acceptable
Additional Information

Test performed by Mayo Medical Laboratories

CPT Code
88271x2, 88291
Reflex CPT
88271 (variable), 88274 x2; 88275