Semen Analysis (WHO Criteria)
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Direct answer
Semen analysis under WHO criteria is the basic laboratory test of male fertility, measuring volume, sperm concentration, motility, vitality and morphology against reference values. Under the 2010 fifth edition, a normal sample has a concentration of at least 15 million sperm per mL, at least 40 per cent total motility and at least 4 per cent normal forms. The sixth edition, published in 2021, revised several lower reference limits (for example concentration 16 million per mL), so the edition used should always be stated.
What you must remember
- Volume: At least 1.5 mL under the 2010 criteria, with a low volume suggesting incomplete collection or obstruction.
- Concentration: At least 15 million per mL, and a total count of at least 39 million per ejaculate.
- Motility: Total motility of at least 40 per cent and progressive motility of at least 32 per cent.
- Vitality: At least 58 per cent live sperm, tested when motility is low.
- Morphology: At least 4 per cent normal forms by strict criteria, which is the fifth-centile lower reference limit.
- Leucocytes: Fewer than 1 million per mL, with higher counts suggesting infection or inflammation.
- Abstinence: Two to seven days recommended before collection, and repeat testing is needed before infertility is diagnosed.
Definitions are the exam, so learn the cut-offs
Semen terms are tested as a set of precise definitions, so the thresholds matter as much as the words. The table gives the standard terms with their cut-offs under WHO 2010 criteria.
| Term | Meaning | Cut-off (WHO 2010) |
|---|---|---|
| Oligozoospermia | Low sperm concentration | Under 15 million per mL |
| Asthenozoospermia | Reduced motility | Progressive motility under 32 per cent |
| Teratozoospermia | Abnormal morphology | Normal forms under 4 per cent |
| Oligoasthenoteratozoospermia | Combined defects | All three present |
| Azoospermia | No sperm in the ejaculate | None, even after centrifugation |
| Necrozoospermia | No live sperm in the ejaculate | Vitality well below 58 per cent, ideally none alive |
Terms are applied only after more than one sample, because a single sample varies widely. Azoospermia is then split into obstructive and non-obstructive forms, with raised FSH and small testes suggesting failure of spermatogenesis.
The 2021 revision makes it essential to state which reference values a report uses. Laboratories should also record the time from collection to analysis, since motility falls with delay.
Where the exam tries to catch you
The most common traps involve edition numbers, single samples and the azoospermia workup.
- Trap: Diagnosing male infertility from one abnormal sample Correct: Counts vary widely, so at least two samples, usually taken weeks apart, are assessed before a diagnosis.
- Trap: Quoting 2010 reference values as the only standard Correct: The 2021 sixth edition revised the limits (concentration 16 million per mL, progressive motility 30 per cent, vitality 54 per cent, volume 1.4 mL), so the edition must be specified.
- Trap: Treating azoospermia without separating obstructive from non-obstructive causes Correct: Normal FSH with normal testicular size suggests obstruction, while raised FSH with small testes points to non-obstructive azoospermia.
Frequently asked questions
What is the WHO 2010 cut-off for normal sperm concentration?
Under WHO 2010 criteria, a normal sperm concentration is at least 15 million sperm per mL. Below this value the term oligozoospermia applies. The total count, which is concentration multiplied by volume, should be at least 39 million per ejaculate.
How is azoospermia classified in semen analysis?
Azoospermia is the absence of sperm in the ejaculate even after centrifugation. It is classified as obstructive or non-obstructive, guided by serum FSH and testicular size. Karyotype and Y chromosome microdeletion testing are often needed in non-obstructive azoospermia.
How many semen samples are needed before diagnosing male infertility?
Two or more semen samples are usually analysed before an abnormality is diagnosed, because counts vary widely from one ejaculate to another. Samples are commonly taken several weeks apart. A single abnormal result alone is not enough to label a man as infertile.
What abstinence period is recommended before semen collection?
The WHO recommends an abstinence period of two to seven days before semen collection. This standardises the sperm count and motility measured. Shorter or longer intervals can change the results.
What does asthenozoospermia mean?
Asthenozoospermia means reduced sperm motility, usually defined as progressive motility below 32 per cent under WHO 2010 criteria. It is distinct from low concentration, which is oligozoospermia. The two defects can occur together.