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Semen Analysis

Infertility is defined as the inability to conceive after 12 months of unprotected intercourse. Infertility affects 1 in 6 couples of childbearing age. In approximately 40% of infertility cases a female factor can be identified and in 40% a male factor. The remaining 20% of cases are due to combination of male and female disorders or remain unexplained. Semen analysis is an important step in the initial evaluation of an infertile couple. Semen analysis is also performed post vasectomy to determine if a patient has become sterile.

The following collection guidelines need to be followed to ensure specimen viability.

  • Physician orders should specify whether the collection is being done for fertility or post-vasectomy testing.
  • Patients should have 2 to 7 days of abstinence prior to collection.
  • A complete specimen should be collected since sperm concentration is highest in the first portion of ejaculate.
  • Lubricants and condoms should not be used for specimen collection because they may contain spermicides.
  • Specimens should be maintained at room temperature after collection.
  • Hospital laboratory must process specimens within 30 minutes after collection.
  • Specimens must arrive at MML within 24 hours after collection.

Semen analysis is performed according to WHO guidelines. Results are interpreted as follows:

  • Appearance of normal semen is a homogeneous gray or creamy opalescent color. Red or brown color may indicate the presence of blood in seminal fluid. A white, turbid appearance may indicate inflammation or infection.
  • Volume of ejaculate is normally 2 to 5 mL. Lower volume may suggest an anatomic abnormality of the genital tract. An increased volume may suggest retrograde ejaculation, in which seminal fluid flows into the bladder.
  • pH is normally 7.2 to 7.8. A more acidic pH suggests an abnormally high ratio of prostatic to seminal fluid. A pH of 8.0 or higher may be associated with infection of the prostate, seminal vesicles or epididymis.
  • Normal sperm count is >20 million per mL. Counts between 10 and 20 million are considered borderline. Sperm count is performed in a Neubauer chamber.
  • Both the percentage of motile sperm and the grade (speed) of motility on a scale of 0 to 4 are reported. Motility speed is classified as rapid progressive, slow progressive, non-progressive or non-motility. A grade of 4 indicates rapid progressive movement. Normal sperm have >50% motility and a grade of 3 or 4. Sperm motility is as important as number. The presence of a large percentage of non-motile spermatozoa may signify either a sperm cell flagellum defect or the presence of dead sperm. Dead sperm can be detected by supravital staining. Poor sperm motility can impede spermatozoa from entering the cervix and moving into the fallopian tubes, decreasing fertility.
  • Sperm morphology is another important evaluation criterion. At least 200 spermatozoa are examined on stained slides using bright field microscopy. An ocular micrometer is used for measuring length and width of spermatozoa. The percentage of abnormal forms is reported. Spermatozoa are examined for defects involving the head, neck, acrosome and tail regions. A spermatozoan is generally considered normal if it has a smooth and oval head measuring 4-5 um in length, an acrosome comprising 40-70% of the sperm head area, symmetrical neck insertion into the head, a mid-piece with no large cytoplasmic droplets, and a uniform tail of regular width and length without coiling or bent configuration. More than 70% of spermatozoa should have normal mature morphology and at least 30% should have normal oval shapes. Abnormalities in head structure are associated with poor ovum penetration. Examples include double heads, giant and amorphous heads, pinheads, tapering heads and constricted heads. Spermatozoan tail defects may impede the migration of spermatozoa through cervical mucus. The presence of aberrant forms in excess of 40% can cause a reduction in fertilizing capacity.
  • Germinal cell count should be <4 million per mL. A higher number of germinal cells indicates a disorder in spermatogenesis because sperm usually mature within the epididymis prior to release. Germinal cells may be referred to as round cells in some reports.
  • Spermatozoa viability is normally >75%. Viability is assessed using a supravital stain.
  • White blood cell count is normally <1 million. Higher counts indicate genital tract infection.

If the patient will be involved in an assisted reproductive program, Kruger Strict Criteria are used to evaluate sperm morphology. Kruger criteria identify three threshold groups based on the percentage of normal spermatozoa: 0-4% normal forms, 5-14% normal forms, and greater than 14% normal forms. These groups are used as a predictive value in determining in vitro fertilization outcomes.

Post-vasectomy semen analysis is much simpler, consisting of only a sperm count. Typically, two semen samples are tested at least six to eight weeks after the vasectomy. Semen analysis involves two steps. First the ejaculate is examined for spermatozoa. If no spermatozoa are seen the specimen is centrifuged at 1000g for 15 minutes and the pelleted sample is reexamined for sperm. In each step, a minimum of 30 high power fields (40x magnification) should be examined. Results are reported as the number of spermatozoa per HPF. Specimens are usually tested at monthly intervals until two consecutive monthly specimens show no spermatozoa.

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