Semen Analysis Health Article

Definition

A semen analysis is the examination of freshly ejaculated seminal fluid. Seminal fluid is a viscous, turbid fluid produced mainly from secretions of the seminal vesicles (45–80% of volume) and prostate gland (15–30% of the volume). About 1% of the total volume is spermatozoa and testicular fluid produced by the testes. A routine analysis of seminal fluid includes the measurement of fluid volume, viscosity, pH, and fructose and measurement of sperm concentration, count, motility, viability, and morphology. Additional tests are performed as indicated. These are usually performed by andrology laboratories and include testing for sperm autoantibodies, zona free hamster oocyte penetration, cervical mucus penetration, the acrosomal reaction test, and computer assisted sperm analysis (CASA).

Purpose

In the United States, the infertility rate for married couples is approximately 15%. A semen analysis is the examination of a male's ejaculate, performed to determine if the cause of a couple's infertility is attributed to the male's inability to fertilize the ovum. It is also used to confirm the absence of sperm following vasectomy. In addition, a microscopic exam for sperm is performed on vaginal swabs and clothing taken in suspected rape cases as part of the crime scene investigation. This is used along with tests for acid phosphatase and prostate specific antigen to determine the presence of seminal fluid.

Precautions

The patient should abstain from intercourse for three days prior sample collection and refrain from drinking alcoholic beverages for at least 24 hours before testing. Antineoplastic agents and estrogen may lower test results. Additionally, several herbal supplements have been found to affect sperm counts and/or characteristics.

A semen specimen to investigate infertility must kept at room temperature. It should be collected by masturbation into a disposable sterile, wide-mouth container. A room close to the testing site is preferred for collection, since specimen quality deteriorates rapidly. If possible, examinations for motility and viability should be performed and smears prepared within one hour of collection. Timing is not as critical for postvasectomy testing. Physiological and environmental factors can increase the variability of semen analysis, and the World Health Organization (WHO) recommends the evaluation of two ejaculates collected at least seven days but not more than three months apart.

Description

Male infertility may be caused by many conditions that affect the production of functional sperm. The most common cause is varicocele (hardening of the veins that drain the testes) which accounts for about 40% of cases and is treated surgically. Testicular failure accounts for approximately 10% of cases and may result from numerous causes including malignancy, mumps, Kleinfelter's syndrome, injury, and radio- or chemotherapy. Hyperspermia, increased seminal fluid volume, also accounts for about 10% of cases. Endocrine diseases affecting spermatogenesis account for approximately 9% of cases and usually involve pituitary or adrenal hypoplasia or hyperthyroidism. Obstruction of the ejaculatory duct accounts for about 5% of cases and sperm autoantibodies for 1–2%.

Physical characteristics of the semen sample that are evaluated include volume, gross appearance (color, turbidity), viscosity, and liquifaction. Seminal fluid will coagulate within five minutes of collection due to coagulating protein secreted by seminal vesicles. The seminal fluid should liquefy within one hour at room temperature, due to the action of prostatic secretions. Failure to do so inhibits motility. After liquifaction, viscosity may be measured by observing the fluid as it drains from the tip of a 5 mL serological pipet. The fluid should flow from the tip in discrete droplets. Formation of a thread of two or more centimeters at the tip indicates abnormally high viscosity. Volume is determined by determining the amount of fluid that can be drawn into a 10 mL serological pipet.

Sperm counting methods

The sperm concentration is usually performed using a 1:20 dilution of seminal fluid in a diluent containing formalin which immobilizes the sperm. Usually five of the 0.2 x 0.2 mm squares of a hemacytometer grid are counted. The number of cells counted is equal to the sperm concentration in millions per mL. All 25 squares are counted if there are less than 10 sperm (spermatozoons) per square. A Mackler chamber, a grid consisting of 1 square millimeter divided into 100 equal squares, (0.1 x 0.1 mm, 0.01 mm deep) can be used in place of a hemacytometer. Undiluted seminal fluid is heated to 50-60°C to immobilize the sperm. Heads are counted in 10 of the squares and the total is equal to the sperm concentration in millions per milliliter. A sperm concentration less than 20 million per milliliter is termed oligozoospermia, and often results from ductal obstruction, regurgitation