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FISH, Prenatal Screen

Test code: 14604

This assay screens for numerical abnormalities of chromosomes 13, 18, 21, X, and Y: trisomy 13, trisomy 18, trisomy 21 (Down syndrome), and sex chromosome abnormalities such as Turner syndrome, Klinefelter syndrome, and triploidy.

The following chromosome disorders are not screened:

  • Aneuploidy of chromosomes other than 13, 18, 21, X, and Y
  • Structural chromosome abnormalities
  • Low-level mosaicism

The American College of Medical Genetics recommends that irreversible therapeutic action should not be taken based on the results of FISH analysis alone. After a positive FISH result, clinical decision-making should be based on additional information, either a confirmatory chromosome analysis or consistent clinical information.1


1. Test and technology transfer committee, American College of Medical Genetics. Technical and clinical assessment of fluorescence in situ hybridization: An ACMG/ASHG position statement. Genet Med. 2000;2(6):356-61.

This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on the physician’s education, clinical expertise, and assessment of the patient.

Document FAQS.59 Version: 1

Version 1: Effective 12/12/2023 to present

Version 0: Effective 05/30/2012 to 12/12/2023