Fertility Tests

Semen Analysis Using the Kruger Strict Criteria

A routine semen analysis typically assesses the volume, concentration, percent motility and progression of the sample. While these components are essential for understanding possible male infertility, sperm morphology determined by the "Kruger strict morphology" method has the greatest correlation to in-vitro fertilization (IVF) success. In fact, the Kruger method is the only morphology scoring system shown to have a clinical predictive value for the sperm fertilizing an egg in IVF.

Reproductive Care Center has the most experience in Utah routinely performing Kruger strict morphology testing as part of the initial semen analysis. RCC also uses the most up to date WHO V (Fifth Edition) criteria. Kruger strict morphology testing can also be completed at the time of intrauterine insemination (IUI) (for an additional cost) if desired. This is often done if an initial semen analysis was completed in an outside lab.

Kruger strict morphology testing can also be completed at the time of intrauterine insemination (IUI) (for an additional cost) if desired. This is often done if an initial semen analysis was completed in an outside lab.

For this test, freshly ejaculated sperm are smeared on a slide and stained using a morphology staining product for human sperm. Sperm are judged as normal based on the following criteria:

  1. Head must be oval in shape with smooth contours, 5-6 µm in length and 2.5 to 3.5 µm wide with the acrosome taking up 40-70% of the head.
  2. Neck and mid-piece must have no abnormalities and a cytoplasmic droplet (a remnant from sperm production) if present must not be larger than half the size of the head.
  3. Tail must not be coiled or bent and should not have a droplet at the end.

After 200 individual sperm are counted at a magnification of 1,000 times, the percent normal forms is calculated. The prognosis is based on the following scale:

>=15% normal: Normal range - Good prognosis
5-14% normal: Sub optimal range - Prognosis is fair to good, however, the lower the percent normal, the lower the chance of successful fertilization
0-4% normal: Poor prognosis - Will usually need IVF with intracytoplasmic sperm injection (ICSI)

The Kruger strict morphology test can be highly subjective, therefore choosing a lab with extensive daily experience that can also correlate the results with fertilization in vitro is extremely important. 

Based on our experience we currently recommend a couple consider IVF with ICSI if the Kruger strict morphology is 5% or lower. Intrauterine insemination is often recommended for couples with Kruger results in the sub optimal but good prognosis range if there are no other factors that would prevent pregnancy.

When a couple is undergoing IVF we usually recommend ICSI if the Kruger strict morphology is 8% of less in order to minimize the likelihood of no fertilization and to maximize the number of eggs that fertilize. Each individual is different and your physician will review the complete semen analysis results in order to make a specific recommendation.

The Andrology Lab at the Reproductive Care Center is supervised by an andrologist with over 10 years experience, assessing over 500-1,000 slides annually. The lab also participates in a proficiency testing program every 6 months, and routinely compares slides scored by Dr. Kruger’s lab.