Semen analysis is used to evaluate male fertilitya man's ability to reproduce. This test, which also is called a sperm count, is used to measure the amount and quality of seminal fluid or ejaculate. Seminal fluid contains male reproductive cells (semen or sperm) and normally is expelled through the penis during ejaculation (sexual climax; orgasm).
Semen analysis also can be used to help diagnose Klinefelter's syndrome, which is the most common congenital (inherited) cause for testosterone deficiency. This condition, which is caused by an extra X chromosome, results in male infertility (inability to conceive after one year of unprotected intercourse), sparse facial and body hair, abnormal breast enlargement (gynecomastia), and small testes. In most cases, at least two sperm counts are performed following vasectomy to look for sperm in the semen.
Semen analysis usually is performed by a fertility specialist. Seminal fluid can affect factors such as sperm shape, function, and movement, so the entire ejaculate is examined.
Prior to semen analysis, ejaculation should be avoided for 2–3 days. The semen sample can be collected in a sterile glass container through masturbation (i.e., sexual stimulation) or through sexual intercourse using a special type of condom provided by the physician.
The sample must be analyzed within 1–2 hours to provide accurate results. Many specialists require three different semen samples to account for factors that can affect results, such as variations in temperature and laboratory errors. It often is recommended that the results of the tests do not vary by more than 20%.
Semen analysis includes the following factors:
- Volume (total volume of ejaculate)
- Standard semen fluid test (e.g., thickness, color, acidity)
- Concentration (sperm count; sperm/mL)
- Morphology (sperm shape and structure; associated with sperm health)
- Motility (% of sperm that show forward movement; mobility)
- Total motile count (total number of moving sperm)
Normally, seminal fluid is clear to milky white in color, thick and sticky (viscous) in consistency, has a pH (acidity) level between 7.8 and 8.0, and contains few or no white blood cells (leukocytes).
The World Health Organization (WHO) has developed the following values for normal semen analysis:
- Total volume—greater than 2 mL
- Concentration—at least 20 million sperm per mL
- Morphology—at least 15% normal sperm
- Motility—greater than 50% sperm with forward movement, or 25% with rapid movement within 1 hour of ejaculation
- White blood cells—fewer than 1 million per mL
- Further analysis (sperm mixed antiglobulin reaction [MAR] test) shows adherent particles in less than 10% of sperm
According to the National Institutes of Health (NIH), approximately 1 couple in 6 has difficulty conceiving. It is estimated that male infertility is a factor in about 30–40% of these cases. The most common cause for infertility in men is an enlarged mass of veins in the spermatic cord within the scrotum (called varicocele). The spermatic cord is made up of veins, arteries, lymphatic vessels, nerves, and the duct that carries sperm from the testes to the seminal vesicles (vas deferens).
Overall, varicocele contributes to approximately 40% of male infertility cases. In men who have fathered a child but are no longer able to do so (a condition called secondary infertility), varicocele is the cause in as many as 80% of cases. Surgery to correct varicocele (called varicocele repair or varicocelectomy) can improve the shape and structure (morphology) of sperm. Following varicocele repair, approximately 50% of men are able to father a child within the first year.
Although semen analysis often can suggest male infertility, the results may not identify the cause for the condition. Additionally, some men with low sperm counts are able to reproduce (i.e., are fertile). In many cases, abnormal semen analysis results require additional testing.