The hamster zona-free ovum test (HZFO test), or hamster egg-penetration test, or sometimes just hamster test, is an

in-vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') studies are performed with cells or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology and its subdis ...

test used to study physiological profile of spermatozoa. The primary application of the test is to diagnose male

infertility In biology, infertility is the inability of a male and female organism to Sexual reproduction, reproduce. It is usually not the natural state of a healthy organism that has reached sexual maturity, so children who have not undergone puberty, whi ...

caused by

sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...

unable to penetrate the

ova , abbreviated as OVA and sometimes as OAV (original animation video), are Japanese animated films and special episodes of a series made specially for release in home video formats without prior showings on television or in theaters, though the ...

. The test has limited value, due to expense and a high

false negative A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test resu ...

rate.

Procedure

In this test, sperm are incubated with several

hamster Hamsters are rodents (order Rodentia) belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera. They have become established as popular small pets. The best-known species of hamster is the golden or Syrian ...

eggs. After seven to twenty hours, the number of sperm penetrations per egg is measured. The hamster eggs have had the

zona pellucida The ''zona pellucida'' (Latin meaning "transparent zone") is the specialized area surrounding mammalian oocytes (eggs). It is also known as an egg coat. The ''zona pellucida'' is essential for oocyte growth and fertilization. The ''zona pelluc ...

, the outer membrane, removed—hence, ''zona-free''. Having all eggs penetrated by multiple sperm is considered to be a positive sign for fertility. Results suggest that men whose sperm fail the hamster test are a third as fertile than those whose sperm pass. Although medical professionals often present the procedure as unable to create an embryo, these claims are not technically correct. If the human sperm succeeds in penetrating the hamster egg, a hybrid embryo is indeed created, known as a humster. These embryos are typically destroyed before they divide into two cells; were they left alone to divide, they would still be unviable.

Legal permit

The practice is made licensable in the United Kingdom by the

Human Fertilisation and Embryology Act 1990 The Human Fertilisation and Embryology Act 1990 (c. 37) is an Act of the Parliament of the United Kingdom. It created the Human Fertilisation and Embryology Authority which is in charge of human embryo research, along with monitoring and licensing ...

Use

The hamster zona-free ovum test was frequently performed by sperm banks when screening potential

sperm donors Sperm donation is the provision by a man of his sperm with the intention that it be used in the artificial insemination or other "fertility treatment" of one or more women who are not his sexual partners in order that they may become pregnant by h ...

. It was particularly useful in assessing the extent to which sperm from a potential donor could penetrate cervical mucus when artificial insemination was principally performed by ICI or IVI, rather than by IUI. It may still be used when the sperm of a donor is intended to be used in IVF procedures because it can illustrate the ease by which the sperm can penetrate the egg. However, owing to the unreliability of these tests and the advancement of computer tests for the screening of sperm, tests by sperm banks using these methods largely fell out of favour during the 1990s.

Significance

Donated sperm and

intracytoplasmic sperm injection Intracytoplasmic sperm injection (ICSI ) is an in vitro fertilization (IVF) procedure in which a single sperm cell is injected directly into the cytoplasm of an egg. This technique is used in order to prepare the gametes for the obtention of embr ...

techniques are considered more strongly for those whose sperm fail this test. This test evaluates the

acrosome reaction For fertilization to happen between a sperm and egg cell, a sperm must first fuse with the plasma membrane and then penetrate the female egg cell to fertilize it. While the fusion of the sperm cell with the egg cell's plasma membrane is relatively ...

of human spermatozoa. However, the incidence of acrosome reaction in freely swimming human sperm does not accurately reflect the fertilizing ability of the sperm. This test has a poor

predictive value Predictive value of tests is the probability of a target condition given by the result of a test, often in regard to medical tests. *In cases where binary classification can be applied to the test results, such yes versus no, test target (such as a ...

for the success of fertilization in IVF treatment at any insemination concentration. No strong correlation has been found between hamster egg penetration rates and the various semen parameters and the role of the hamster egg penetration test in the investigation of the causes of infertility should be evaluated further. However, a negative result on the hamster test correlates with a lower probability of the man's partner becoming pregnant.

References

{{reflist Medical tests Fertility medicine Semen

Procedure

Legal permit

Use

Significance

See also

References