What is being tested?
A complete semen analysis measures the quantity and quality of the fluid released during ejaculation. It evaluates both the liquid portion, called semen or seminal fluid, and the microscopic, moving cells called sperm. It is often used in the evaluation of male infertility. A shorter version of this test checks solely for the presence of sperm in semen a few months after a man has had a vasectomy to determine whether the surgery was successful.
Semen is a viscous, whitish liquid that contains sperm and the products from several glands. It is fairly thick at ejaculation but thins out, or liquefies, within 10 to 30 minutes. Sperm are reproductive cells in semen that have a head, midsection, and a tail and contain one copy of each chromosome (all of the male's genes). Sperm are motile, normally moving forward through the semen. Inside a woman's body, this property enables them to travel to and fuse with the female's egg, resulting in fertilization. Each semen sample is between 1.5 and 5.5 milliliters (about one teaspoon) of fluid, containing at least 20 million sperm per milliliter, and varying amounts of fructose (a sugar), buffers, coagulating substances, lubricants, and enzymes that are intended to support the sperm and the fertilization process.
A typical semen analysis measures:
Volume of semen
Viscosity—consistency or thickness of the semen
Sperm count—total number of sperm
Sperm concentration (density)—number of sperm per volume of semen
Sperm motility—percent able to move as well as how vigorously and straight the sperm move
Number or percent of normal and abnormal (defective) sperm in terms of size and shape (morphology)
Coagulation and liquefaction—how quickly the semen turns from thick consistency to liquid
Fructose—a sugar in semen that gives energy to sperm
Number of immature sperm
Number of white blood cells (cells that indicate infection)
Additional tests may be performed if the sperm count is low, if the sperm show decreased motility or abnormal morphology, or if the seminal fluid is found to be abnormal. These additional tests may help identify abnormalities such as the presence of sperm antibodies, abnormal hormone levels (testosterone, FSH, LH, prolactin), excessive number of white blood cells, and genetic tests for conditions that may affect fertility, such as Klinefelter syndrome, cystic fibrosis, or other chromosomal abnormality.
In some instances, imaging tests such as ultrasound, CAT scan, or MRI may be required. A biopsy of the testicle may also be needed. Sometimes a test called cryosurvival is done to see how well semen will survive for long-term storage if a couple would like to store sperm for future pregnancies.
How is the sample collected for testing?
Post-vasectomy sperm check: a semen sample is collected in a clean, wide-mouth container provided by the lab.
Infertility evaluation: Most laboratories require samples to be collected on-site as the semen needs to be examined within 60 minutes after ejaculation in order to maintain the quality of the specimen.
Semen is collected in a private area by self-stimulation. Some men, for religious or other reasons, might want to collect semen during the act of intercourse, using a condom. If this is the case, the healthcare practitioner should provide the condom or sheath because lubricated condoms can affect test results.
Sperm are very temperature-sensitive. If collection is done at home, the sample should be kept at body temperature (98.6oF/37oC) by keeping it next to the body during transportation. It should not be left at room temperature for an extended period of time and should not be refrigerated.
Sperm motility decreases after ejaculation; thus, timing and temperature are critical to obtaining accurate results. If the sample is poor, repeat testing might be needed.
Is any test preparation needed to ensure the quality of the sample?
For infertility testing: To give sperm a chance to replenish, abstain from ejaculating for 2 to 5 days before the sample is collected. Longer periods of abstinence may result in a greater volume of semen but decreased sperm motility. You may also be asked to avoid alcohol consumption for a few days before the test as well. Follow any instructions that are provided.
Post-vasectomy: Men may be advised to have regular ejaculations every 3-4 days to clear sperm from the reproductive tract more quickly.