The test, developed from a technique used on bull semen, works much like a home pregnancy test, with results that check against a colour chart. The man deposits a sample of semen into a vial, which he 'incubates' at body temperature in a beaker for an hour.
The kit has a dye that changes from purple to pink when oxygen in the sample falls below a certain level. The more vigorous the sperm, the more oxygen they consume. So a sample that holds lots of active sperm will turn pale pink.
When couples have difficulty conceiving, the problem lies with the man as often as with the woman. It is usually the woman, however, whose fertility is checked first. The developers hope that their kit will spare many women the distress of such tests.
'We hope it will take away a lot of marital stress,' the co-developer, Frank Comhaire, head of endocrinology at the Academic Hospital in Ghent, Belgium, says in a report in today's issue of New Scientist.
The test draws on work on bull semen by a team of German veterinarians. A test for humans had to be far more sensitive, since bull sperm are stronger and more active than human ones.
The scientists have found that in a millilitre of semen, 20 million highly mobile sperm are needed to turn the sample pink. At this level of fertility, a couple would have a 90 per cent chance of conceiving within a year. Semen of infertile men, containing fewer than 10 million mobile sperm per millilitre, will cause no colour change.
Dr Comhaire and Robert Ericsson, an independent biologist based in Florida, did the fine tuning needed for a human version of the test.
Men whose test result is negative or uncertain are advised to try again before consulting a doctor. A pack of two tests costs about pounds 20.Reuse content