Non-Invasive
Prenatal Screening

What is 22q11.2 deletion syndrome?

Also known as DiGeorge syndrome, 22q11.2 deletion syndrome is caused by a submicroscopic deletion (microdeletion) on the long arm of chromosome 22. Most cases are de novo (new mutations), and approximately 10% are inherited. Inherited cases follow an autosomal dominant pattern, with a 50% chance of having an affected child.

How do we test for 22q11.2 deletion syndrome?

22q11.2 deletions are usually too small to be identified with standard cytogenetic studies (karyotype). Typically, it can be diagnosed by FISH or microarray.

Why is it important to screen for 22q11.2 deletion?

22q11.2 deletion is the most common microdeletion syndrome, occurring in as many as 1 in 1,000 pregnancies,¹ and is the second most common cause of developmental delay after Down syndrome.²

Conventional screening methods, such as first-trimester screening, do not reliably detect 22q11.2 deletion in the prenatal period.² Additionally, maternal age is not a risk factor for microdeletions, meaning that 22q11.2 deletion syndrome can occur in any pregnancy.¹ Studies have shown that early prenatal screening for 22q11.2 deletion, combined with diagnosis, allows for appropriate medical management of the pregnancy, as well as for the child in the neonatal period and into childhood.³

What are the clinical implications of 22q11.2 deletion screening?

The features of this syndrome vary widely. Common signs and symptoms include heart abnormalities, immune deficiency, characteristic facial features, developmental delays, along with some laboratory biochemical abnormalities. 

Are all pregnancies eligible for 22q11.2 deletion screening?

The 22q11.2 deletion screening option has been validated in singleton pregnancies, including IVF self and non-self-egg donor pregnancies. This test has not been validated in pregnancies with more than one fetus. Women with a known 22q11.2 deletion are not eligible for this test.

When is 22q microdeletion screening available?

Like Harmony NIPT screening, 22q11.2 deletion can be ordered anytime from 10 weeks gestation until delivery. 22q11.2 microdeletion screening can only be ordered with Harmony NIPT screening and cannot be ordered on its own.

Is Harmony a quality choice for detecting 22q11.2 deletion?

Clinical validation studies for the Harmony Prenatal Test with 22q11.2 show a sensitivity of 75% and a specificity of 99.5%.⁴ This corresponds to a “false positive rate” of 0.5%. Therefore, the combined false positive rate for Harmony trisomies 21, 18, 13 with 22q11.2 still remains exceptionally low, at less than 0.6%.^4,5

How should the test results be interpreted?

A 22q11.2 deletion may not be detected in all fetuses. Due to the limitations of the test, a “No Evidence of a Deletion” result does not guarantee that a fetus is unaffected by a chromosomal or genetic condition. For “High Probability” results, similar to all positive NIPT chromosomal conditions, confirmatory testing is necessary for diagnosis. It is appropriate to offer genetic counselling, including a discussion of potential risks to offspring and reproductive options, to patients who are affected or at risk.

For information on how to order Harmony NIPT with 22q11.2 deletion, click here.

Non-invasive prenatal testing (NIPT) based on cell-free analysis is not diagnostic; results should be confirmed by diagnostic testing. Before making any treatment decisions, all women should discuss their results with their healthcare provider, who can recommend confirmatory, diagnostic testing where appropriate. The Harmony Prenatal Test is developed by Ariosa Diagnostics and is performed in Australian Clinical Labs in Australia.

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