Interpretive Handbook

Test 81409 :
Newborn Aneuploidy Detection, FISH

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Approximately 1/2 of clinically recognizable spontaneous abortions have a major chromosomal anomaly.


Up to 95% of chromosomal abnormalities diagnosed prenatally involve aneuploidy (gain or loss of whole chromosome) of chromosomes 13, 18, 21, X, and Y.


In liveborn infants, about 8/1,000 have a major chromosome anomaly, of which 6.5/1,000 involve aneuploidy of 1 of these 5 chromosomes.


Diagnosis of chromosomal disorders can be performed by chromosome analysis of uncultured blood, standard chromosome study, and the technique utilizing FISH based on interphase cells. Standard chromosome analysis takes 3 to 10 days and analysis from uncultured newborn blood is often unsatisfactory and labor-intensive. FISH based methods facilitate rapid diagnosis of aneuploidy and may be helpful in medically urgent evaluations of newborn infants suspected to have aneuploidy of 1 of these chromosomes.

Useful For Suggests clinical disorders or settings where the test may be helpful

Ruling out aneuploidy of chromosomes 13, 18, 21, X, and Y in a rapid, cost-efficient manner

Interpretation Provides information to assist in interpretation of the test results

An interpretive report will be provided.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test does not detect chromosomal aneuploidies other than 13, 18, 21, X, and Y or any structural anomaly.


Low levels of mosaicism involving chromosomes 13, 18, 21, X, or Y may not be detected by this procedure.


The use of these probes has been approved by the FDA as a stand-alone test. However, we would strongly recommend that a complete chromosome analysis be performed in conjunction with this diagnostic procedure (CMS / Chromosome Analysis, for Congenital Disorders, Blood). In cases where the FISH analysis is normal, a chromosome analysis allows identification of more complex abnormalities and the less common numeric abnormalities of other chromosomes. In cases where the FISH study is abnormal, chromosome analysis can determine whether the abnormality is due to aneuploidy or a complex structural abnormality. Conventional chromosome analysis allows calculation of a more accurate recurrence risk for the family.

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.

An interpretive report will be provided.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Whiteman DAH, Klinger K: Efficiency of rapid in situ hybridization methods for prenatal diagnosis of chromosome abnormalities causing birth defects. Am J Hum Genet 1991;49:A1279

2. Maeda T, Ohno M, Matsunobu A, et al: A cytogenetic survey of 14,835 consecutive liveborns. Jap J Hum Genet 1991;36:117-129

3. Jalal SM, Law ME, Dewald GW: Atlas of Whole Chromosome Paint Probes. Normal Patterns and Utility for Abnormal Cases. Rochester, MN, Mayo Foundation, 1996