To facilitate the understanding of concepts pertaining to the rationale for semen analysis and sperm function and their interpretation, the following narrative outline is provided:

Fertilization involves direct sperm-egg union. Essentially, sperm must be able to reach the fertilization site (possess adequate sperm motility and sperm morphology). Sperm must also be in sufficient numbers within the semen (sperm concentration) to overcome the statistical improbabilities of finally reaching the egg. The first obstacle in the female reproductive system is the cervical mucus. Sperm must penetrate and migrate through the cervical mucus (evaluated by a sperm mucus penetration assay).

Sperm, during passage through the female reproductive system, must undergo membrane alteration known as sperm capacitation. Once the sperm reach the egg, the spermatozoa must undergo further membrane alteration leading to acrosome reaction, which is dependent on the functional integrity of the membrane itself (evaluated by a hypoosmotic swelling assay). Sperm must then bind and penetrate the zona pellucida (evaluated by a hemizona assay) prior to fusing with the egg's vitelline membrane (evaluated by a sperm penetration assay).

According to the prescribed sperm function sequence, male fertility potential can best be evaluated in a similarly logical and sequential manner. In summary, the following panel of tests are suggested:

Sperm quality panel

Are the spermatozoon able to reach the fertilization site? Routine semen analysis and a satisfactory post-coital test or sperm mucus penetration assay are tests which enable that determination.

Sperm function panel

Are the spermatozoon able to fertilize an egg? Hypoosmotic swelling assay, hemizona assay and sperm penetration assay allow that determination.

Antisperm antibody test panel

Are immunological factors suspected? Antisperm antibodies have been implicated in 10-20% of unexplained infertility cases. Such a test panel should assess all three effects of antisperm antibodies (sperm agglutination, sperm immobilization and sperm surface binding).

Chemical analysis of seminal plasma panel

Based on preliminary semen analysis, do chemical components need to be assessed? Such a panel assesses fluid contribution from the epididymis, seminal vesicle, and prostate. The pH level is also determined.

Additional tests

Which other tests are required? Based on semen analysis, overall medical history and clinical findings from the spouse, other special testing such as spermatozoon ultrastructural evaluation, nuclear integrity assessment, biochemical analysis of spermatozoa, karyotyping, microdeletion in the Y chromosome determination or any other sophisticated sperm assays should be conducted, as indicated.