Y-Chromosome Microdeletion Test
A Y-chromosome microdeletion test looks for missing DNA in the AZF regions of the Y chromosome that are important for sperm production. It is mainly used in men with non-obstructive azoospermia or very severe oligozoospermia. The result can directly change treatment: complete AZFa or AZFb deletions are associated with essentially no chance of finding sperm by testicular extraction, whereas AZFc deletion has a variable outcome and sperm may be present in semen or retrieved from the testis. If sperm from an AZFc-deleted man are used for ICSI, male children will inherit the deletion.
What are AZFa, AZFb and AZFc?
The azoospermia factor (AZF) regions lie on the long arm of the Y chromosome and contain genes needed for spermatogenesis. A microdeletion removes DNA too small to be seen on an ordinary karyotype, so a separate molecular test is needed.
| Deletion | Typical fertility implication |
|---|---|
| Complete AZFa | Usually severe Sertoli-cell-only pattern; testicular sperm retrieval is essentially futile |
| Complete AZFb | Usually severe maturation arrest; sperm retrieval is essentially futile |
| Large deletions including AZFa/AZFb | Very poor/zero retrieval prognosis; TESE should not be performed |
| AZFc | Most common; phenotype ranges from severe oligozoospermia to azoospermia; testicular sperm may be retrievable |
| Partial/atypical deletions | Interpretation can be more complex and should be handled by an experienced genetics/andrology team |
Who should be tested?
EAU guidance recommends Y-chromosome microdeletion testing in men with sperm concentrations of 1 million/mL or less and advises considering testing below 5 million/mL. Men with confirmed NOA are a key group. The test is not useful as a general screening test for every man with mild low count.
How is the test done?
It is a blood DNA test. The laboratory uses validated PCR-based markers to detect clinically relevant deletions. Quality control matters because incomplete or non-standard marker panels can lead to confusing results. A genetics laboratory experienced in infertility testing is preferable.
How does the result affect micro-TESE?
A complete AZFa or AZFb deletion is one of the few findings that can confidently prevent an unnecessary sperm-retrieval operation. AZFc is different: EAU guidance notes that testicular sperm can be found in roughly half to three-quarters of men with AZFc deletions across published series, although individual success cannot be guaranteed.
Inheritance and ICSI
The Y chromosome is passed from father to son. Therefore, a son conceived using sperm from a man with an AZFc deletion will inherit the deletion and may face impaired fertility as an adult. This is why genetic counselling is an essential part of using such sperm for ICSI.
Does a negative Y-microdeletion test rule out a genetic cause?
No. It only excludes the clinically tested Y-chromosome deletions. Karyotype abnormalities, monogenic conditions and currently unexplained genetic causes can still exist. The test should therefore be integrated with karyotype, hormones and clinical findings when indicated.
What if sperm are already present in semen?
In men with severe oligozoospermia and an AZFc deletion, ejaculated sperm may be cryopreserved because counts can fluctuate and decline. The fertility team may plan ICSI using stored ejaculated sperm and reserve surgical retrieval as backup if needed.
Why the exact AZF region matters
A report should identify which azoospermia-factor region is deleted. Complete AZFa or AZFb deletions are associated with an extremely poor likelihood of retrieving sperm and can prevent an unnecessary surgical search. AZFc deletions are different: sperm may be present in the ejaculate or testis in some men, so fertility treatment can still be possible.
If sperm from a man with an AZFc deletion are used for ICSI, a male child can inherit the same Y-chromosome deletion and may face infertility later. The phrase ‘Y deletion positive’ is therefore not enough for counselling; the exact region and genetic interpretation matter.
Testing is most useful when the clinical picture suggests severely impaired sperm production, such as non-obstructive azoospermia or selected men with very severe oligozoospermia. It is not a general screening test for every mildly abnormal semen analysis.
The result should ideally be reviewed before micro-TESE so that prognosis, inheritance and the need for genetic counselling are understood before an invasive procedure is undertaken.
Emergency warning signs
A Y-chromosome microdeletion result is not an emergency, but it can materially affect sperm-retrieval planning and should be reviewed before procedures are booked. Acute scrotal pain, swelling, fever/redness or trauma still requires urgent medical care.
What to bring for consultation
Bring these if available:
- Semen analysis reports with actual concentration or azoospermia confirmation.
- FSH, LH and testosterone.
- Karyotype report.
- Y-microdeletion report with exact AZF region.
- Previous sperm-freezing or micro-TESE records.
- Genetic counselling notes if already seen.
FAQs
Can AZFc deletion have sperm in semen?
Yes. The phenotype ranges from severe oligozoospermia to azoospermia, so some men have ejaculated sperm.
Can micro-TESE find sperm with AZFa deletion?
With a complete AZFa deletion, sperm retrieval is essentially zero and TESE is not recommended.
Will my son inherit an AZFc deletion?
Yes. A male child inherits his father’s Y chromosome, including the deletion.
Is Y-microdeletion the same as a karyotype?
No. Karyotype detects chromosome number and large structural changes; Y-microdeletion testing detects smaller losses in the AZF regions.
Should men with 8 million sperm/mL get this test?
Routine yield is low above 5 million/mL. Testing is usually focused on azoospermia and very severe oligozoospermia unless other clinical features justify it.
Related reading
- Genetic Testing in Male Infertility
- Non-Obstructive Azoospermia
- Klinefelter Syndrome and Infertility
- Micro-TESE Surgery Explained
- Sperm Freezing: When Should Men Consider It?
- Urologist in Latur
References
- European Association of Urology. EAU Guidelines on Sexual and Reproductive Health: Male Infertility. 2026 https://uroweb.org/guidelines/sexual-and-reproductive-health/chapter/male-infertility
- American Urological Association/American Society for Reproductive Medicine. Diagnosis and Treatment of Infertility in Men: AUA/ASRM Guideline (2020; Amended 2024) https://www.auanet.org/documents/Guidelines/PDF/2024%20Guidelines/Male%20Infertility%20Unabridged%20Final.pdf