What Does Mixed Antiglobulin Reaction (MAR Test) Mean?
Mixed antiglobulin reaction (MAR) is a test used to detect the presence of anti-sperm antibodies (ASA) on sperm. It is thought that when antibodies bind to the membrane of sperm, they can damage sperm, decrease sperm motility or hinder transportation through the reproductive tracts or otherwise interfere with fertilization.
FertilitySmarts Explains Mixed Antiglobulin Reaction (MAR Test)
There are two ways of detecting ASA through the MAR test:
- Direct MAR: which detects antibodies bound to the sperm cells
- Indirect MAR: which detects antibodies present in the serum (serum is blood from which clotting factors have been removed) or semen plasma (the fluid only part of semen without cells)
Direct MAR or Immunobead Tests
The direct MAR test involves mixing fresh, untreated (direct MAR) or washed (immunobead) semen with latex particles coated with a type of human antibody (immunoglobulin A or G ) called IgA or IgG. The antibody to the antibody, called anti-IgA or anti-IgG is then added to the mixture of fresh, untreated sperm and latex beads.
These antibody-coated particles will recognize and attach to the region of the sperms wherever the anti-sperm antibodies (of the IgG type) are located.
Typically if 50% or more of the sperm binds to the Ig, it is considered positive and requires follow up testing.
Indirect MAR (Sperm MAR)
The indirect MAR is done by adding washed motile sperm from a donor (screened to be free of antibodies) to the patient’s diluted serum. The mixture is incubated at 37°C for an hour. Then a drop of this mixture is processed as in a regular MAR test by mixing it with coated latex particles and anti-IgG. After 2 to 3 minutes, the percentage of motile sperm that bind to the antibodies (IgG) is recorded.
Pros and Cons
The Direct MAR/immunobead tests are convenient, quicker, and require less volume of ejaculate. The indirect MAR test is more sensitive (yields fewer false-positives) and accurate, hence, it appears to be an ideal procedure to screen for sperm antibodies in serum.