Sperm DNA Fragmentation Testing: When It Is Useful and What Its Limits Are

Sperm DNA fragmentation (SDF) testing is increasingly requested by couples and clinicians. It can add useful information in selected cases, but it is not a routine test for every man, and its results must be interpreted carefully.

Key takeaways

• Sperm DNA fragmentation testing measures breaks in sperm DNA that a routine semen analysis does not assess.
• EAU guidelines suggest considering the test in couples with recurrent pregnancy loss and in men with unexplained infertility.
• There is no universal cut-off, and results from different methods (SCSA, TUNEL, SCD, Comet) are not interchangeable.
• ESHRE does not recommend routine testing before ART, so the test should be used where the result will change management.

What sperm DNA fragmentation means

A standard semen analysis assesses concentration, motility and morphology, but not the integrity of the sperm's genetic material. DNA fragmentation means breaks in the sperm DNA strands. High levels have been associated with lower natural fertility and with pregnancy loss in some studies.

Possible causes include:

• Varicocele
• Smoking, heat exposure and other lifestyle factors
• Infection and inflammation
• Older age
• Some medications and treatments such as chemotherapy

Main test methods

• SCSA (Sperm Chromatin Structure Assay): uses flow cytometry
• TUNEL: labels DNA breaks directly
• SCD (Sperm Chromatin Dispersion, or Halo test): a microscope-based test often used in clinical laboratories
• Comet assay: detects single- and double-strand breaks

Each method measures something slightly different, and thresholds are not interchangeable between tests or laboratories.

When testing may be useful

European urology guidelines (EAU) suggest that SDF testing can be considered in:

• Couples with recurrent pregnancy loss
• Men with unexplained infertility

It may also be discussed in men with varicocele or repeated unsuccessful ART cycles, as part of a wider assessment.

The limits of the test

• There is no single, universally agreed cut-off value
• Methods and results vary between laboratories
• Evidence that treating a high result improves live birth rates is limited
• ESHRE's good practice recommendations on IVF add-ons do not recommend routine SDF testing before ART

For these reasons, SDF testing should be used selectively, where the result will change management, and not as a routine screen.

Managing a high result

Options depend on the cause and the clinical picture, and may include:

• Lifestyle changes such as stopping smoking and avoiding heat exposure
• Treating infection
• Assessment of a clinical varicocele by a urologist
• Discussion of ART options, recognising that evidence for specific laboratory strategies is still evolving

Laboratory quality

Like any andrology test, SDF results are only as reliable as the laboratory method. Standardised protocols, internal quality control and trained staff are essential.

Frequently asked questions

Should every man have a DNA fragmentation test?

No. It is a selective test, best used when the result will change the advice given, such as in recurrent pregnancy loss or unexplained infertility.

Is the Halo test the same as TUNEL or SCSA?

No. They are different methods with different thresholds, so results from one test cannot be directly compared with another.

Can a high DNA fragmentation level improve?

In some men it improves after removing risk factors or treating an underlying cause, but this is not guaranteed.

Learn advanced andrology at ReproNest

ReproNest's Andrology & Semen Analysis Course covers WHO 6th edition semen analysis, sperm function testing including DNA fragmentation assays, sperm preparation and cryopreservation. Read our male infertility work-up guide, or contact us.

This article is educational content for healthcare professionals and trainees. It is not medical advice and does not replace clinical judgement, current guidelines or the ART (Regulation) Act 2021 and Rules 2022.