For the man with a
poor semen sample, additional tests which may recommended
include specialized sperm tests; blood tests; and testis
biopsy.
Antisperm Antibodies Test The role of antisperm antibodies
in causing male infertility is controversial, since
no one is sure how common or how serious this problem
is. However, some men (or their wives) will possess
antibodies against the sperm, which immobilize or kill
them and prevent them from swimming up towards the egg.
The presence of these antibodies can be tested in the
blood of both partners, in the cervical mucus, and in
the seminal fluid. However, there is little correlation
between circulating antibodies (in the blood) and sperm-bound
antibodies (in the semen).
There are many methods of performing this test, which
can be quite difficult to standardize, as a result of
which there is a lot of variability between the result
reports of different laboratories. The older methods
of testing used agglutination methods on slides and
in test tubes.
Perhaps, the best method available today is one such
uses immunobeads, which allow determination of the location
of the antibodies on the sperm surface. If they are
present on the sperm head they can interfere with the
sperm’s ability to penetrate the egg; if they
are present on the tail they can retard sperm motility.
Of course, if the test is negative, this is reassuring;
the problem really arises when the test is positive!
What this signifies and what to do about it are highly
vexatious issues in medicine today, and doctors are
even more confused about this aspect than the patients.
Semen Culture Test Ion the semen culture test, the
semen sample is tested for the presence of bacteria,
and , if present, their sensitivity to antibiotics is
determined. Interpreting this test can also be problematic!
It is normal to find some bacterial in normal semen
samples - and the question which must be answered is
: are these bacteria disease- causing or not?
Tests which assess the sperm’s ability "
to perform" include the following sperm function
tests.
Postcoital Test (PCT) The postcoital test is the easiest
test of sperm function, since it is performed in vivo.
It is done when the wife is in the " fertile"
period, during which time the cervical mucus is profuse
and clear. The gynecologist examines a small sample
of the cervical mucus, under the microscope, a few hours
after intercourse. ( This can be embarrassing and awkward
for the patient, but it is not painful at all). Finding
5-10 motile sperm per high power microscopic field means
that the test is normal. A normal test implies normal
sperm function and can be very reassuring.
An abnormal test needs to be repeated and, if the problem
is persistent, one needs to determine if the defect
lies in the sperm or in the mucus, by cross-testing
with the husband’s sperm, donor sperm, wife’s
mucus and donor mucus.
Bovine Cervical Mucus Test The bovine cervical mucus
test is another form of testing for the ability of the
sperm to penetrate and swim through cervical mucus,
with the difference that in this case, the mucus used
is that of a cow (since this is commercially available
abroad in a test kit.) The sperm are placed in a column
of cervical mucus and how far the sperm can swim forward
through the column in a given amount of time is checked
with the help of a microscope.
Sperm Viability or Sperm Survival Test This is a simple
test, which provides crude (but useful!) information
on the functional potential of the sperm. The sperm
are washed using the same method which is used for IVF
(either a Percoll spin or sperm swim up) and the washed
sperm are then kept in a culture medium in the laboratory
incubator for 24 hours. After 24 hours, the sperm are
checked under the microscope. If the sperm are still
swimming actively, this means that they have the ability
to "survive" in vitro for this period- and
this is reassuring. If, however, none of the sperm are
alive after 24 hours, this suggest that they may be
functionally incompetent.
Sperm Penetration Assay (SPA, Hamster Assay) Since
the basic function of a sperm is to fertilize an egg,
scientists were very excited when they found that normal
sperm could penetrate a denuded (zona-free) hamster
egg. A zona-free hamster egg is obtained from hamsters
egg. A zona-free hamster egg is obtained from hamsters
and the covering (the zone) removed by using special
chemicals. The egg are then incubated with the sperm
in an incubator in the laboratory. After 24 hours, the
eggs are checked to ascertain how many sperm have been
able to penetrate the egg. The result gives a penetration
score, which gives an index of the sperm’s fertilizing
potential. This is a very delicate technique and is
not available in India. In any case, nowadays scientists
the world over are quite disenchanted with the test,
since the correlation between IVF results (the ability
to fertilize human eggs) and the SPA (the ability to
penetrate zona-free hamster eggs) is quite poor.
Testing for acrosomal status HOS test - hypo-osmotic
swelling test-which tests for the integrity of the sperm
membrane CASA - computer-assisted sperm analysis Hemizona
assay Electron microscopy of sperm The aforementioned
tests are highly sophisticated and are not easily available.
Another drawback is that these tests are often not standardized
adequately, so that interpreting their results can be
quite difficult.
The ultimate sperm function test is the IVF, since
this directly assesses whether or not the husbands"
sperm can fertilize the wife’s eggs. The best
way to perform this test is to culture some of the eggs
with the husband’s sperm and the others with donor
sperm of proven fertility, at the same time. If the
donor sperm can fertilize the eggs, and the husband’s
sperm fail to do so, then the diagnosis of sperm inability
to fertilize the egg is confirmed. However, even this
test is not infallible, since it has been shown that
about 5% of sperm samples which fail to fertilize an
egg in the first IVF attempt, can do so in a second
attempt at IVF. In any case, it is obviously not practicable
or feasible to use IVF as a test for sperm function
in clinical practice.
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