Skip to content
Inciteful Med

Diagnosing and Understanding Tests

Published: | Updated:

Chromosomal Microarray (CMA) is the gold standard diagnostic test for 22q11.2 deletion syndrome, as it detects exactly where the deletion starts and ends. Prenatal NIPT is only a screening test and requires postnatal confirmation.

Key Takeaways

  • • Chromosomal Microarray (CMA) is the gold standard diagnostic test because it scans the genome at high resolution to find exact deletion boundaries.
  • • Prenatal NIPT is an initial screening test that evaluates risk, but it requires a confirmatory diagnostic test.
  • • Older targeted testing like FISH is effective for typical cases but can miss smaller deletions that CMA would catch.
  • • Because symptoms overlap with other conditions like CHARGE Syndrome, 22q11.2DS is often initially misdiagnosed as an isolated heart defect or speech delay.
  • • Your definitive genetic report should include genomic coordinates, the deletion size in megabases, and whether the TBX1 gene is involved.

Getting to a diagnosis of 22q11.2 deletion syndrome can be a journey. For some families, it happens before birth or shortly after; for others, it may take years of piecing together different health challenges [1]. Understanding the tools used to find the deletion can help you navigate medical records and advocate for the right care.

How the Diagnosis is Made

  • Prenatal Screening: Non-Invasive Prenatal Testing (NIPT) or cell-free DNA (cfDNA) analyzes tiny pieces of fetal DNA found in the mother’s blood [2]. While very good at identifying risks, it is a screening test and requires confirmation [3].
  • Chromosomal Microarray (CMA): This is the current gold standard diagnostic test [4]. It scans the entire genome at a very high resolution and tells doctors exactly where the deletion starts and ends [5][6].
  • FISH (Fluorescence In Situ Hybridization): This is an older, targeted test [7]. It uses a glowing probe to see if a specific piece of Chromosome 22 is missing. While effective for “typical” cases, FISH can miss smaller deletions that a microarray would easily catch [4][8].

Overlapping Conditions and Misdiagnosis

22q11.2DS is often called “the great pretender” because its symptoms overlap with many other conditions [1].

  • Overlapping Conditions: The syndrome is sometimes misdiagnosed as other genetic conditions like CHARGE Syndrome, which shares similar features such as heart defects and palate/ear issues. Doctors often test for multiple conditions to be sure [9].
  • Isolated Findings: Sometimes a person is diagnosed with just an “isolated” heart defect or a “simple” speech delay, and the underlying genetic cause isn’t looked for until more symptoms appear in adulthood [10][11].

Reading Your Genetic Report

Your genetic pathology report is a critical piece of your medical history. A definitive report should include these key data points:

  • Genomic Coordinates: The exact “map locations” on Chromosome 22 where the deletion begins and ends (e.g., chr22:18,912,231-21,465,672) [7][12].
  • Deletion Size: Usually measured in megabases (Mb). A typical deletion is about 3 Mb, but some are smaller (1.5 Mb) [7][13].
  • The Build: The version of the “human genome map” used for the test (often listed as Hg19 or Hg38) [7]. This helps doctors compare results accurately over time.
  • Genes Involved: Confirmation that the TBX1 gene is included in the deleted area, as this gene drives many of the syndrome’s physical features [13][7].

Frequently Asked Questions

What is the best test to diagnose 22q11.2 deletion syndrome?
Chromosomal Microarray (CMA) is currently the gold standard diagnostic test. It scans the entire genome at a very high resolution and shows exactly where the chromosome deletion begins and ends.
Can prenatal blood tests definitively diagnose the syndrome?
Non-Invasive Prenatal Testing (NIPT) using the mother's blood is highly effective but it is only a screening test. Any positive result indicating a risk for the syndrome must be followed up with a confirmatory diagnostic test.
Why might a FISH test miss a 22q11.2 deletion?
While FISH is an effective targeted test for typical deletions, it is an older technology. It can miss smaller or atypical deletions that a more comprehensive chromosomal microarray would easily detect.
What key information should be on my genetic pathology report?
A complete report should list the specific genomic coordinates of the deletion, its size in megabases, the genome build used for the test, and confirmation of whether the TBX1 gene is missing.
Why is 22q11.2 deletion syndrome frequently misdiagnosed?
The condition is often called the great pretender because its features, such as heart defects or palate issues, overlap with other genetic conditions like CHARGE Syndrome. Sometimes it is misdiagnosed as an isolated speech delay or heart defect until more symptoms emerge.

Questions for Your Doctor

  • • Was the diagnosis confirmed with a Chromosomal Microarray (CMA) or a FISH test, and what are the limitations of that specific test?
  • • Does the genetic report specify the exact genomic coordinates and confirm whether the TBX1 gene is included in the deletion?
  • • Are there any other genetic variations or 'copy number variants' on the report that might be influencing the symptoms?
  • • If the initial screening was a prenatal NIPT, has a confirmatory postnatal diagnostic test been performed?

Questions for You

  • • What were the initial symptoms or medical findings that led to the recommendation for genetic testing?
  • • Do I have a full, physical copy of the genetic pathology report to share with all future specialists?

Want personalized information?

Type your question below to get evidence-based answers tailored to your situation.

References

  1. 1

    22q11.2 deletion syndrome.

    McDonald-McGinn DM, Sullivan KE, Marino B, et al.

    Nature reviews. Disease primers 2015; (1()):15071 doi:10.1038/nrdp.2015.71.

    PMID: 27189754
  2. 2

    Performance of a targeted cell-free DNA prenatal test for 22q11.2 deletion in a large clinical cohort.

    Bevilacqua E, Jani JC, Chaoui R, et al.

    Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology 2021; (58(4)):597-602 doi:10.1002/uog.23699.

    PMID: 34090308
  3. 3

    Expanding the fetal phenotype: Prenatal sonographic findings and perinatal outcomes in a cohort of patients with a confirmed 22q11.2 deletion syndrome.

    Schindewolf E, Khalek N, Johnson MP, et al.

    American journal of medical genetics. Part A 2018; (176(8)):1735-1741 doi:10.1002/ajmg.a.38665.

    PMID: 30055034
  4. 4

    De Novo Interstitial Deletion of 9q in a Pediatric Patient With Global Developmental Delay.

    Keselman D, Singh R, Cohen N, Fefer Z

    Child neurology open 2019; (6()):2329048X19844920 doi:10.1177/2329048X19844920.

    PMID: 31106228
  5. 5

    Inverted duplication, triplication and quintuplication through sequential breakage-fusion-bridge events induced by a terminal deletion at 5p in a case of spontaneous abortion.

    Chai H, Grommisch B, DiAdamo A, et al.

    Molecular genetics & genomic medicine 2019; (7(10)):e00965 doi:10.1002/mgg3.965.

    PMID: 31478360
  6. 6

    Analytical and clinical performance of chromosomal microarrays compared with FISH panel and conventional karyotyping in patients with chronic lymphocytic leukemia.

    Tang Z, Kanagal-Shamanna R, Tang G, et al.

    Leukemia research 2021; (108()):106616 doi:10.1016/j.leukres.2021.106616.

    PMID: 34022744
  7. 7

    22q and two: 22q11.2 deletion syndrome and coexisting conditions.

    Cohen JL, Crowley TB, McGinn DE, et al.

    American journal of medical genetics. Part A 2018; (176(10)):2203-2214 doi:10.1002/ajmg.a.40494.

    PMID: 30244528
  8. 8

    Improved assay performance of single nucleotide polymorphism array over conventional karyotyping in analyzing products of conception.

    Lin SB, Xie YJ, Chen Z, et al.

    Journal of the Chinese Medical Association : JCMA 2015; (78(7)):408-13.

    PMID: 26004737
  9. 9

    Cardiovascular Malformations in CHARGE Syndrome with DiGeorge Phenotype: Two Case Reports.

    Yasuda K, Morihana E, Fusazaki N, Ishikawa S

    Case reports in pediatrics 2016; (2016()):8013530 doi:10.1155/2016/8013530.

    PMID: 27957375
  10. 10

    Aortic Arch Laterality in Chromosome 22q11.2 Deletion Syndrome: Male-Female Difference.

    Evans WN, Acherman RJ, Restrepo H

    Clinical pediatrics 2023; (62(4)):345-348 doi:10.1177/00099228221127730.

    PMID: 36214167
  11. 11

    Prevalence of chromosomal abnormalities and 22q11.2 deletion in conotruncal and non-conotruncal antenatally diagnosed congenital heart diseases in a Chinese population.

    Kong CW, Cheng YKY, To WWK, Leung TY

    Hong Kong medical journal = Xianggang yi xue za zhi 2019; (25(1)):6-12 doi:10.12809/hkmj187552.

    PMID: 30655461
  12. 12

    Chromosome 22q11.2 Deletion Syndrome: A Comprehensive Review of Molecular Genetics in the Context of Multidisciplinary Clinical Approach.

    Szczawińska-Popłonyk A, Schwartzmann E, Chmara Z, et al.

    International journal of molecular sciences 2023; (24(9)) doi:10.3390/ijms24098317.

    PMID: 37176024
  13. 13

    The 22q11.2 deletion syndrome: Genetic mechanisms, clinical manifestations, and therapeutic strategies.

    Yang S, Zhuang Y, Xin S, et al.

    Clinica chimica acta; international journal of clinical chemistry 2026; (586()):120893 doi:10.1016/j.cca.2026.120893.

    PMID: 41690495

This page provides educational information about genetic testing for 22q11.2 deletion syndrome. Always review your specific genetic pathology report and test results with a qualified genetic counselor or medical geneticist.

Stay up to date

Get notified when new research about 22q11.2 deletion syndrome is published.

No spam. Unsubscribe anytime.