Sperm Function Tests or Functional Assays

Examinations of sperm function, also known as functional assays, are exclusively conducted in specialized andrology laboratories. The absence of standardization introduces complexity into result interpretation. When employed individually, a singular sperm function test may not yield significant insights for fertility assessment. However, their predictive efficacy is notably enhanced when utilized in combination.

Postcoital (Sims-Huhner) Test

The Postcoital (Sims-Huhner) Test involves the assessment of cervical mucus following coitus to evaluate the sperm's ability to penetrate the cervical mucus. Cervical mucus quality fluctuates throughout the menstrual cycle, reaching peak abundance and fluidity during ovulation, primarily influenced by estrogen. This increased fluidity facilitates sperm penetration through the mucus. In the secretory phase, progesterone augments mucus viscosity. Therefore, cervical mucus testing is strategically scheduled just before ovulation, determined by basal body temperature records or follicular sizing through ultrasonography.

The Postcoital Test, a traditional method for identifying the cervical factor in infertility, entails aspirating cervical mucus with a syringe shortly before the expected ovulation time and 2-12 hours post-coitus. Gross and microscopic examinations are conducted to evaluate cervical mucus quality, considering elasticity and drying patterns, along with assessing the number and motility of sperm (refer to Box 1). A test is deemed normal if ≥ 10 motile sperms are observed.

An abnormal test may result from factors such as poor cervical mucus quality due to incorrect ovulation judgment, cervicitis, or treatment with antioestrogens (e.g., Clomid). It may also be attributed to the absence of motile sperms, stemming from ineffective coitus technique, lack of ejaculation, poor semen quality, use of coital lubricants harmful to sperm, or the presence of antisperm antibodies. Antisperm antibodies can cause immotile sperms, agglutination, or clumping and may be present in either partner.

If a cervical factor is identified, intrauterine insemination emerges as a popular treatment option. However, the medical literature disputes the definitive value of the postcoital test.

This test can be carried out if semen analysis indicates normal parameters, and the female partner is in the ovulatory phase with unobstructed fallopian tubes. Additionally, the test is administered when there is suspicion of antisperm antibodies, and the male partner declines to undergo semen analysis.

Cervical Mucus Penetration Test

The Cervical Mucus Penetration Test involves measuring the maximum distance traveled by sperm in seminal fluid placed and incubated within a capillary tube containing bovine mucus. Typically, the majority of fertile men exhibit a score exceeding 30 mm, whereas most infertile men demonstrate scores below 20 mm.

Hamster Egg Penetration Assay

The Hamster Egg Penetration Assay involves enzymatic treatment of hamster oocytes to eliminate outer layers inhibiting cross-species fertilization. Subsequently, these treated oocytes are incubated with sperm and observed for penetration rates. Results can be reported as either (a) the number of eggs penetrated, with a penetration rate of <15% indicating low fertility, or (b) the number of sperm penetrations per egg, where a normal value is >5. This assay assesses sperm motility, binding to the oocyte, and the penetration of the oocyte. It's important to note a relatively high occurrence of false-negative results associated with this test.

Hypo-osmotic Swelling of Flagella

This examination evaluates the functional integrity of the sperm's plasma membrane by observing the curling response of flagella under hypo-osmotic conditions.

Computer-assisted Semen Analysis

Computer program is used to measure diverse characteristics of spermatozoa; however, its role in predicting fertility potential remains unconfirmed.