Male fertility · London
Sperm DNA fragmentation test, the piece a normal semen analysis misses.
A private SDF test in London, reported alongside a full WHO semen analysis where useful. We match you to an HFEA-licensed andrology laboratory and a fertility consultant who acts on the result.
DFI reference ranges
- Normal <15%
- Intermediate 15-30%
- High >30%
DNA fragmentation index reported after SCSA, TUNEL, Comet or SCD (Halo) assay.
What SDF measures
The DNA inside the sperm, not just the sperm itself.
A high fragmentation index is associated with reduced natural fertility, higher miscarriage risk, and poorer IVF and ICSI outcomes, particularly during embryo development after fertilisation.
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TUNEL
Terminal deoxynucleotidyl transferase dUTP nick end labelling. Direct measurement of DNA strand breaks. Widely used in research and clinical andrology.
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SCSA
Sperm Chromatin Structure Assay. Flow cytometry after acid denaturation. Reports the DNA fragmentation index (DFI) and remains the reference assay in many UK laboratories.
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Comet
Single-cell gel electrophoresis. Sensitive to both single and double strand breaks. Alkaline and neutral variants give complementary information.
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SCD (Halo)
Sperm Chromatin Dispersion. Simple microscopy-based test. Sperm with fragmented DNA fail to form the characteristic halo of dispersed chromatin.
Why SDF rises
Oxidative stress, heat, and the passage of time.
Most causes are reversible or treatable. The commonest pattern in London clinics is a combination of age, lifestyle and an undiagnosed varicocoele.
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Advanced paternal age
DFI climbs steadily beyond 40, and more sharply beyond 45.
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Varicocoele
Elevated scrotal temperature and oxidative stress. See our guide to varicocoele embolisation.
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Infection
Chronic prostatitis and epididymitis raise reactive oxygen species in the ejaculate.
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Lifestyle oxidative stress
Smoking, obesity, heavy alcohol, hot baths, saunas, tight clothing and prolonged cycling.
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Systemic disease
Poorly controlled diabetes, chronic inflammatory disease, prior cancer treatment.
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Occupational exposure
Solvents, pesticides, heavy metals and sustained radiant heat.
Who should test
SDF is not routine, but it is not niche either.
A normal WHO 6th edition semen analysis does not rule out sperm DNA damage. If the picture below fits, the test earns its place in the workup.
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Unexplained infertility with a normal WHO 6th edition semen analysis
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Recurrent pregnancy loss (RPL) after two or more miscarriages
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Recurrent IVF or ICSI failure, particularly poor embryo development after fertilisation
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Known or suspected varicocoele
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Advanced paternal age, typically above 45
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Lifestyle risk factors: smoking, obesity, occupational heat or chemical exposure
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Before choosing between conventional IVF and ICSI
If the DFI is high
A staged plan, from lifestyle to laboratory.
Spermatogenesis takes about 74 days, so most interventions need three months before a repeat SDF test is meaningful.
- 01
Lifestyle first
Stop smoking, reduce alcohol, lose weight, avoid hot baths and saunas, loosen underwear, reduce prolonged cycling. Three months of consistent change covers a full cycle of spermatogenesis.
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Antioxidant supplementation
Vitamin C, vitamin E, zinc, selenium, CoQ10, L-carnitine and folate. Cochrane evidence is mixed but reasonable to trial for three to six months.
- 03
Shorten abstinence
Two to four days rather than five to seven. Older sperm sitting in the epididymis accumulate oxidative DNA damage.
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Varicocoele repair
Embolisation or microsurgical repair where a clinical varicocoele is present and DFI is elevated.
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ICSI over IVF
When DFI is high, ICSI is usually preferred, though very high DFI (>50%) may not be fully overcome by ICSI alone.
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Testicular sperm (TESE)
Testicular sperm bypasses epididymal transit and often shows lower DNA damage. Considered in extreme SDF above 50%.
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Advanced sperm selection
MACS (magnetic-activated cell sorting), PICSI and IMSI enrich for healthier sperm within an ICSI cycle.
A complete male workup
SDF sits inside a broader picture.
A WHO 6th edition semen analysis (count, motility, morphology) is the foundation. SDF and DFI add the DNA integrity layer. A hormone profile checks testosterone, FSH, LH, prolactin and SHBG. A scrotal ultrasound looks for a varicocoele, hydrocoele or testicular pathology.
Where the count is very low or absent, genetic testing (Y chromosome microdeletion and karyotype) is added. Anything abnormal earns a private urology or andrology consultation. Pulse Atlas coordinates the sequence so nothing is repeated and nothing is missed.
Indicative pricing
Honest ranges across HFEA-licensed labs.
Prices vary by assay, laboratory and whether a consultant appointment is included. We come back with a firm quote within one working day.
| Test or workup | Indicative range |
|---|---|
| SDF / DFI test (SCSA, TUNEL, Comet or Halo) | £180-£380 |
| WHO 6th edition semen analysis + SDF combined | £280-£450 |
| Male hormone panel (testosterone, FSH, LH, prolactin, SHBG) | £150-£280 |
| Scrotal ultrasound for varicocoele | £220-£380 |
| Genetic workup (Y microdeletion + karyotype) | £350-£650 |
| Comprehensive male fertility workup with urology consult | £550-£950 |
London providers
HFEA-licensed labs and fertility clinics we work with.
A small vetted panel across central London. Introductions made privately, once we understand your case.
- The Lister Fertility Clinic
- CARE Fertility London
- ARGC (Assisted Reproduction & Gynaecology Centre)
- TFP The Fertility Partnership
- King's Assisted Conception (Private)
- Andrology Solutions
- Concept Fertility Clinic
- HFEA-licensed andrology laboratories across central London
Frequently asked
The six questions we hear most about SDF.
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What is a sperm DNA fragmentation (SDF) test?
SDF measures the percentage of sperm carrying damaged DNA. The result is reported as the DNA fragmentation index (DFI). Below 15% is normal, 15 to 30% is intermediate, and above 30% is high and linked to reduced fertility, higher miscarriage risk and poorer IVF and ICSI outcomes.
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How is the SDF test different from a standard semen analysis?
A WHO 6th edition semen analysis reports count, motility and morphology. It does not assess the integrity of the DNA inside each sperm. Two men with identical semen analyses can have very different DFI results, which is why SDF is often added when infertility is unexplained.
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Which assay is best: TUNEL, SCSA, Comet or Halo?
SCSA and TUNEL are the most established and reproducible. Comet is sensitive but more technical. SCD (Halo) is simple and widely available. The choice usually reflects the laboratory rather than the clinical question. Consistency matters more than the specific assay.
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When should I consider an SDF test?
Consider it if you have unexplained infertility, two or more miscarriages, recurrent IVF or ICSI failure, a known varicocoele, are over 45, or have significant lifestyle risk factors such as smoking, obesity or occupational heat exposure.
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What can I do if my DFI is high?
Lifestyle change first: stop smoking, lose weight, reduce alcohol, avoid hot baths and prolonged cycling. Consider a three to six month course of antioxidants, shorten abstinence to two to four days, and repair a varicocoele if present. If DFI stays high, discuss ICSI, testicular sperm retrieval (TESE) and advanced sperm selection such as MACS or PICSI with your fertility consultant.
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How much does an SDF test cost privately in London?
The SDF test alone typically costs £180 to £380. Combined with a WHO semen analysis, expect £280 to £450. A comprehensive male fertility workup including hormones, scrotal ultrasound and a urology consultation usually falls between £550 and £950.
Speak to a fertility concierge
One clinician, from first message to final result.
We arrange the SDF test at an HFEA-licensed London laboratory, add the full WHO semen analysis and any hormone or ultrasound work you need, and route the results to a fertility consultant who can act on them.