Fig 2. The anatomy of a sperm.

If there are enough sperms. If the sample has less than 20 million sperm per ml, this is considered to be a low sperm count. Less than 10 million is very low. The technical term for this is oligospermia (oligo means few). Some men will have no sperms at all and are said to be azoospermic. This can come as a rude shock because the semen in these patients look absolutely normal - it is only on microscopic examination that the problem is detected.

Whether the sperms are moving well or not ( sperm motility) . The quality of the sperm is often more significant than the count. Sperm motility is the ability to move. Sperm are of 2 types – those which swim, and those which don’t. Remember that only those sperm which move forward fast are able to swim up to the egg and fertilise it – the others are of little use. Motility is graded from a to d, according to the World Health Organisation ( WHO) Manual criteria , as follows. Grade a ( fast progressive) sperms are those which swim forward fast in a straight line - like guided missiles. Grade b ( slow progressive) sperms swim forward, but either in a curved or crooked line, or slowly (slow linear or non linear motility) . Grade c ( nonprogressive) sperms move their tails, but do not move forward ( local motility only). Grade d ( immotile ) sperms do not move at all . Sperms of grade c and d are considered poor. Why do we worry about poor motility ? If motility is poor, this suggests that the testis is producing poor quality sperm and is not functioning properly – and this may mean that even the apparently motile sperm may not be able to fertilise the egg.

Whether the sperms are normally shaped or not - what is called their form or morphology. Ideally, a good sperm should have a regular oval head, with a connecting mid-piece and a long straight tail. If too many sperms are abnormally shaped (round heads; pin heads; very large heads; double heads; absent tails) this may mean the sperm are abnormal and will not be able to fertilise the egg. Many labs use Kruger "strict " criteria ( developed in South Africa ) for judging sperm normality. Only sperm which are "perfect" are considered to be normal. A normal sample should have at least 15% normal forms ( which means even upto 85% abnormal forms is considered to be acceptable !)

Sperm clumping or agglutination. Under the microscope, this is seen as the sperms sticking together to one another in bunches. This impairs sperm motility and prevents the sperms from swimming upto through the cervix towards the egg.

Putting it all together, one looks for the total number of "good" sperms in the sample - the product of the total count, the progressively motile sperm and the normally shaped sperm. This gives the progressively motile normal sperm count which is a crude index of the fertility potential of the sperm. Thus, for example, if a man has a total count of 40 million sperm per ml; of which 40% are progressively motile; and 60% are normally shaped; then his progressively motile normal sperm count is : 40 X 0.40 X 0.60 = 9.6 million sperm per ml. If the volume of the ejaculate is 3 ml, then the total motile sperm count in the entire sample is 9.6 X 3 = 28.8 million sperm.

Whether pus cells are present or not. While a few white blood cells in the semen is normal, many pus cells suggests the presence of seminal infection.

Some labs use a computer to do the semen analysis. This is called CASA, or computer assisted semen analysis. While it may appear to be more reliable ( because the test has been done "objectively" by a computer), there are still many controversies about its real value, since many of the technical details have not been standardised, and vary from lab to lab.

A normal sperm report is reassuring, and usually does not need to be repeated. If the semen analysis is normal, most doctors will not even need to examine the man, since this is then superfluous. However, remember that just because the sperm count and motility are in the normal range, this does not necessarily mean that the man is "fertile". Even if the sperm display normal motility, this does not always mean that they are capable of "working" and fertilising the egg. The only foolproof way of proving whether the sperm work is by doing IVF ( in vitro fertilisation) !

Poor sperm tests can results from

incorrect semen collection technique , if the sample is not collected properly, or if the container is dirty

too long a time delay between providing the sample and its testing in the laboratory

too short an interval since the previous ejaculation

recent systemic illness in the last 3 months (even a flu or a fever can temporarily depress sperm counts)

If the sperm test is abnormal, this will need to be repeated 3-4 times over a period of 3-6 months to confirm whether the abnormality is persistent or not . Don’t jump to a conclusion based on just one report - remember that sperm counts do tend to vary on their own ! It takes six weeks for the testes to produce new sperm - which is why you need to wait before repeating the test. It also makes sense to repeat it from another laboratory, to ensure that the report is valid.

What if the sperm count is persistently poor ? Then other tests may be advised, to try to pinpoint what the problem is; and these are described in the next chapter.