SKY test – Spectral Karyotyping

SKY test – Spectral Karyotyping

Spectral karyotyping (also known as SKY) is a technique that allows “coloring” the chromosomes using special dyes to make it easier to identify the chromosome pairs.

SKY tests allow a more efficient and precise identification of the chromosomes than regular karyotyping, which improves the chances of identifying translocations and chromosome abnormalities.

What is a SKY test?

The SKY technique is based on conventional karyotyping –one of the most common and important genetic tests, that allows identifying the chromosomes and their structure. Karyotyping helps present the chromosomes and conduct a morphologic analysis to search for abnormalities. 

Karyotyping is considered efficient and inexpensive, but it requires trained personnel and experience to notice the small changes. SKY testing is based on fluorescent marking via specific markers that attach to each chromosome, this makes it easier to accurately identify translocations and changes that may go undetected in conventional karyotyping.

It is important to note that in most cases, a conventional karyotyping is sufficient and SKY testing is not necessary, so spectral karyotyping is a less common test.

When is the test needed?

Spectral karyotyping is not commonly used, and today other genetic testing methods are preferred. There are, however, certain cases in which SKY tests are recommended for getting to the right genetic diagnosis:

Unclear karyotype results

In cases where karyotype results are unclear, or when the results do not enable definite conclusions, a SKY test can certainly be used for an easier identification of chromosome abnormalities. 

Since karyotyping is commonly performed by lab technicians, there are some cases in which chromosome abnormalities are hard to identify, or they are too small to identify in this method. SKY testing is based on dying the chromosome using small markers that enable an easier and improved identification of these disorders.


Chromosomal abnormalities in tumor cells can provide information on possible treatment and prognosis. In many cases patients are recommended a SKY test for a quick and efficient identification of the chromosomal changes that can assist their treatment.

Further genetic testing

Spectral karyotyping can be undergone after undergoing a conventional karyotype test. These cases include amniocentesis or CVS performed as part of prenatal screening, testing for balanced translocations, and other tests. In these cases, SKY testing can allow a faster and more accurate understanding of the results, although it does not always add new information that can help the diagnosis process.


The importance of SKY testing

Spectral karyotyping is important because it allows an easier identification of chromosome aberrations. While conventional karyotyping can take several hours to interpret, SKY tests allow a clear identification of translocations and aberrations.

Since in spectral karyotyping each chromosome is dyed a different color, this test makes it easier to find translocations and aberrations, that show as uneven dying of the chromosome.

In addition, SKT tests are easier to perform, so apart from getting faster results, it can also be performed by less experienced healthcare personnel.

Although SKY tests are not very common today, they may soon become more following the rise in the need for genetic testing and the decrease in test prices. These changes could make SKY tests part of routine genetic testing, which will allow improved results in genetic screening.

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