Sperm Penetration Assays (SPA, “Hamster Tests”)

 There have been many attempts made to develop a Laboratory test that will accurately predict the ability of a human sperm to fertilize a human egg. Dr. Aitken and his group many years ago demonstrated a correlation between sperm movement characteristics and sperm fertilizing ability as evaluated by the zona pellucida-free hamster egg penetration test. In this test, the species specific barrier to penetration (not fertilization) is removed from the ova (eggs) of the hamster. These oocytes are then exposed to prepared sperm from the man being tested. One of the most widely used accessory tests in the evaluation of advanced sperm function, the fusion between human sperm and the hamster oocyte (egg) is nearly identical to that occuring with the human egg. Fusion with the vitelline membrane of the oocyte is normally initiated by the healthy sperm’s plasma membrane that lies over a special section (equatorial segment) of the sperm head in a sperm that has prepared itself for normal fertilization. This test relies upon the ability of sperm that are tested in the laboratory to undergo the necessary reactions to fertilize an egg. Because the sperm prepare themselves in a slightly different manner in the laboratory than in the body, false negatives (fail in the hamster test but normally fertilize the partner’s human egg) have been reported. This test may be used as a screen to asist in determining which men may need the assistance of “ICSI” fertilization. There is some feeling that if a man’s sperm are able to penetrate the hamster eggs in the laboratory, there is a higher likelihood that his sperm will ultimately be able to fertilize a human egg if so exposed. This test is not uniformly accepted, due to the high false negative (no penetration of the hamster egg, but wife gets pregnant anyway) rate and the sometimes seen false positive (penetrates the hamster egg but does not fertilize human eggs in vitro) rate of this test. Global experience has been that good performance in the hamster test can provide some limited reassurance of the likelihood that a man’s sperm will be able to achieve fertilization if given the chance. If men fail the hamster test, most centers rely upon in vitro fertilization with ICSI. This protocol has provides excellent success rates in men whose sperm function remains questionable. It should be noted that most men that fail the hamster test, are able to achieve normal fertilization with ICSI.

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4 Comments

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4 responses to “Sperm Penetration Assays (SPA, “Hamster Tests”)

  1. Hi, I arrived at this site by on a fluke when I was exploring on Google then I came onto your web site. I must tell you that your site is very cool I love your theme! Currently have much free-time at the moment to read through your sitebut I bookmarked it. I will be back in a day or two. Thanks for a great site.

  2. thestoughtons

    My husband was one of the lucky ones to score a 0% on the SPA test. We have yet to conceive naturally but other than that his sperm look really good. Is this article saying, we have a chance of a natural pregnancy? And is there any research as to ways to help his sperm penetrate an egg besides IVF with ICSI?

    • goralgandhi

      HEPT(Hamster egg penetration test) has a high false positive and false negative rate. It has therefore proved to be an insensitive and unreliable assay in identifying subfertile males. You could therefore still have a chance of natural pregnancy if all other factors of infertility are ruled out.
      HEPT seems to be just a useful screening test for prediction of IVF outcome. ICSI is found to achieve normal fertilization with those with a negative penetration test.

  3. Karen W

    goralgandhi,
    I know this post is a few months old, but I was hoping for your advice. Husband had borderline ok normal counts (volume, motility) but only 6% normal morphology based on WHO standards. Our RE recommended this test before we start IUI. We pay out of pocket for everything and this test is $250. With such a high false positive/negative rate is it worth it to do this test? If it was more reliable it would make sense… but I am questioning it’s value now. Thanks so much

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