Análisis de semen

What is a sperm test?

A sperm test is also called a semen analysis. This is when a sample of ejaculate (semen) is examined under a microscope, to look for the number, shape, and movement of sperm cells.

It's used to test for fertility problems in men, and also used after a vasectomy to determine if the procedure has been successful or not.

How do I produce semen for a sperm test?

• You will be given a specimen pot. Produce semen by masturbation into the pot. Do not use semen from a condom.

• Your doctor may ask you not to ejaculate (through masturbation or having sex) for a certain amount of time before you produce the sample. Usually this means you should not have ejaculated for at least 48 hours beforehand. The length of time you are asked to abstain from having sex may vary - your hospital should give you information on this. However, no more than seven days should have gone by since the last time you ejaculated.

  • This is because producing a sample too soon after the last ejaculation can make the sperm count appear lower than it normally is, and producing a sample too long after the last ejaculation can lead to a buildup of 'old' sperm in the sample.

• Ideally, you should deliver the sample to the laboratory within one hour of production. Usually the laboratory will want to know in advance of when you are going to arrive.

• The pot which contains the sample should not be left out in the cold but should be kept warm - for example, in a jacket pocket.

• If you live more than half an hour or so away from the laboratory, your clinic may be able to offer you a suitable private room where you can produce your sample.

What is a normal result?

The amount of semen is measured. There is usually between 1.5-4 mls. The sample is then looked at with a microscope in order to:

• Count the number of sperm.

• Look at the shape of sperm.

• Determine the percentage that are actively moving (motile).

In the test report, these are usually reported as the sperm concentration, the sperm morphology, and the sperm motility respectively.

The results can help detect whether there are any problems with the sperm likely to cause difficulties for a couple trying to get pregnant (infertilidad). Home testing kits are available but they only measure the number of sperm present. They do not measure any of the other factors and can miss common causes of male infertility.

The results of the test generally fall into one of three categories:

• Normal.

• Definitely abnormal. This may mean that:

  • There are very few sperm (oligospermia) or no sperm (azoospermia).

  • The shape and size of sperm (this is referred to as sperm 'morphology') are not normal (teratozoospermia).

  • Very few of the sperm are moving normally (asthenozoospermia).

  • It is not unusual for an abnormal result to be due to a combination of the above.

• Somewhere 'in between'. The more normal sperm there are and the higher the percentage that are actively moving, the greater the chance of fertility.

Your doctor should be able to explain what your results mean.

If the test results show that the specimen was not normal, you may be asked to repeat the process. This is because sperm production can vary due to a number of different factors. If a semen analysis does need to be repeated, it is usual to wait for three months. This is because it takes three months for a new cycle of sperm to be made.

Sometimes, if the sperm count is only mildly abnormal, some of the following factors may be worth considering:

• Was the sample ideal? See above on how to produce an ideal sample. It may be worth repeating to check this. Was it taken to the laboratory in time? Was it kept warm? Cooling the sample or a delay in getting it to the laboratory can alter the number of active sperm and give a false result.

• High temperature of testicles (testes). Sperm are made in the testes, which are in the scrotum. This is the body's way of keeping the testes slightly cooler than the rest of the body, which is best for making sperm. It is often advised for men who have a low sperm count to wear loose-fitting underpants and trousers and to avoid very hot baths, saunas, etc. This aims to keep your testes slightly cooler than the rest of your body, which is thought to be good for sperm production. It is not clear whether these measures improve a man's fertility.

• Smoking can affect the sperm count. If you smoke, you should stop completely for optimum sperm production.

• Alcohol. More than fourteen units per week (equivalent to about seven pints of normal-strength beer or fourteen small glasses of wine) may interfere with optimum fertility.

• Obesidad. Men who have a índice de masa corporal (IMC) of 30 or more are likely to have reduced fertility. Losing weight may help.

• Medicines and drugs. Most do not interfere with sperm production but some may do. These include: sulfasalazine, nitrofurantoin, tetracyclines, cimetidine, colchicine, allopurinol, some chemotherapy medicines, cannabis, cocaine and anabolic steroids. If you have a low sperm count, tell a doctor if you take any medicines or drugs regularly.

After a vasectomy

Semen analysis is done after a vasectomy to check that the procedure has worked. After a vasectomy, you must use alternative forms of contraception until testing has shown that the vasectomy has been successful.

Semen analysis is usually done at least 12 weeks after the procedure, and after at least 20 ejaculations - to get rid of any sperm from before the procedure that are remaining in the tubes.

The results of the post-vasectomy semen analysis may show:

• No sperm at all in the sample. This indicates that the procedure has been successful, and that you are sterile.

• Mobile (active) sperm cells in the sample. This indicates that the procedure was unsuccessful, and you need to continue using alternative contraception.

• Non-mobile sperm cells in the sample. If this happens, you will usually be asked to repeat the sample later. If the second sample shows a low number of non-mobile sperm cells, it means that you are exceptionally unlikely to be capable of producing a pregnancy, and are usually given 'special clearance' to stop using alternative contraception.