Antisperm Antibody Test (ASAB)

Definition - What does Antisperm Antibody Test (ASAB) mean?

An antisperm antibody test detects the presence of antibodies that attack sperm cells in blood, semen or vaginal fluid in a male or female. Antisperm antibodies are produced by the immune system in some people when sperm cells come into contact with white blood cells. High levels of antisperm antibodies in semen or vaginal fluid can lead to clumping or the destruction of sperm by immune cells, limiting the ability of sperm to fertilize an egg, and is a known cause for infertility.

FertilitySmarts explains Antisperm Antibody Test (ASAB)

Antibodies are protein molecules produced by white blood cell and play an important role in the immune system. The function of antibodies is to bind to infectious organisms such as bacteria, viruses, and fungus that enter the body and make these invaders targets for immune cells that destroy them.

In some people, when sperm come into contact with white cells in the blood, it can trigger an immune reaction leading to the production of antisperm antibodies. In men, this can be after an injury to the testes, surgery, testicular biopsy or infection. Women can develop a reaction similar to an allergic reaction after sperm enter the vagina or cervix.

When antibodies bind to sperm, sperm cells lose their mobility. When the antibody concentration is high, it causes sperm to stick together and form clumps. Sperm cells that have antisperm antibodies bound to the surface also signal the immune system to activate immune cells that destroy the sperm. This ultimately results in the sperm losing the ability to swim towards the fallopian tubes to fertilize an egg.

Tests that detect antisperm antibody levels are used to evaluate infertility in both men and women. For men, if a semen analysis shows any sperm abnormality such as reduced movement or formation of clumps, an antisperm antibody test is generally performed. Similarly for women, if a postcoital test shows an abnormal interaction between the cervical mucus and sperm, an antisperm antibody test is done to see if the underlying cause for the abnormality is the presence of antisperm antibodies.

There are two types of antisperm antibody testing.

  • Direct testing - Male semen is analyzed for the presence of antibodies bound to sperm cells
  • Indirect testing - Male or female blood is tested for antisperm antibodies
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