Semen analysis

Principle

• Macroscopic and microscopic evaluation of the ejaculate to assess male fertility and confirm success of vasectomy, following the WHO laboratory manual (6th edition, 2021).

Specimen

• Collect after 2–7 days of sexual abstinence by masturbation into a clean, wide-mouthed, non-toxic container.
• Ordinary latex condoms and lubricants are unsuitable (they can harm sperm).
• Deliver to the lab within about 1 hour, kept at 20–37 °C; record abstinence time, collection time and any spillage.
• At least two samples are advised, as results vary between ejaculates.

Procedure

• Allow liquefaction at 37 °C (normally within about 15–30 minutes; over 60 minutes is abnormal); assess appearance, viscosity, volume (weighing is preferred) and pH.
• Motility: examine a wet preparation within 1 hour of collection, classifying at least 200 sperm as rapidly progressive, slowly progressive, non-progressive or immotile.
• Vitality: eosin–nigrosin stain (dead sperm take up eosin and stain pink-red; live sperm remain unstained) or hypo-osmotic swelling test.
• Concentration: dilute and count in an improved Neubauer hemocytometer.
• Morphology: stained smear (e.g. Papanicolaou or rapid Romanowsky stain) using strict (Tygerberg) criteria.

Results

• WHO 2021 lower reference limits (5th centiles for fertile men): volume 1.4 mL, concentration 16 million/mL, total sperm number 39 million per ejaculate.
• Total motility (progressive + non-progressive) 42%, progressive motility 30%, vitality 54%, normal forms 4%.
• pH is typically 7.2 or higher; peroxidase-positive leukocytes above 1 million/mL suggest inflammation.
• Terms: oligozoospermia (low count), asthenozoospermia (low motility), teratozoospermia (abnormal forms), azoospermia (no sperm).

Quality control and pitfalls

• Values below the 5th centile do not by themselves prove infertility, and values above it do not guarantee fertility.
• Cold exposure or delay reduces motility; incomplete collection lowers volume and count.
• Participate in internal and external QC for counting and morphology.

Clinical use

• Infertility work-up, post-vasectomy confirmation of azoospermia and monitoring of treatment.