And only a fifth of the 436 men turned up for both of the tests needed to finally put them in the clear, according to a study carried out by researchers at the Cleveland Clinic Glickman Urological Institute in Ohio, USA.
Of the 75 per cent that did attend their first, eight-week test, a quarter provided samples that still contained sperm. 80 of the 83 men were producing nonmotile (present but inactive) sperm, but three were producing motile (present and active) sperm, including one who was eventually diagnosed with a vasectomy failure.
65 of the 80 men producing nonmotile sperm were clear at their 12-week checks, but six months after their procedure eight men were still producing positive sperm samples. By ten months, all but the vasectomy failure were finally in the clear.
"Our results show that only three-quarters of the men in the study turned up for their eight-week sperm test, which means that a quarter of them had no idea whether the procedure had worked and whether their partner could still fall pregnant" says lead author Dr Nivedita Dhar, Chief Resident in Urology at the Clinic.
"It is impossible to assess the true vasectomy failure rate in the full study sample as many failed to turn up for follow-up tests, despite careful counselling.
"But what concerns us most is that a quarter of the men who had vasectomies did not return for any tests, despite us stressing the important of these follow-ups" adds Dr Dhar.
According to the researchers up to 90 per cent of urologists require two semen samples to confirm sterility and up to 95 per cent request further samples if nonmotile sperm are present. Doctors recommend that couples use additional contraception until vasectomy patients receive the all clear.
"The result of the study are consistent with other research which has estimated that non-compliance among vasectomy patients is between 25 and 40 per cent" says Dr J Stephen Jones, vice chairman of the Glickman Urological Institute, who directed the study.
"It may, however, be possible to improve full compliance among those who return for at least one test by simplifying the follow-up tests in line with current medical evidence and making sure that this is backed up by adequate counselling.
"For example, our study found that 65 of the men tested at eight weeks needed re-testing, but this fell to 15 when it came to the 12-week test. This suggests that a single test at 12 weeks may be adequate in the majority of cases.
"However, it is very important to stress that couples need to use additional contraception until the vasectomy patient has been given the all clear."
To speak to the authors contact Vicky Agnew,
Senior Media Relations Manager, Cleveland Clinic
00 (1) 216-444-0898 firstname.lastname@example.org
Notes to editors
Determining the success of vasectomy. Nivedita Bhatta Dhar, Amit Bjatt and J Stephen Jones. Glickman Urological Institute, Cleveland Clinic, Ohio, USA. BJU International. Volume 97. Pages 773-776. (April 2006).
Cleveland Clinic Glickman Urological Institute is a not-for-profit multi-speciality academic medical center in Ohio that integrates clinical and hospital care with research and education. Together with Cleveland Clinic Florida it employs full-time 1,5000 physicians representing more than 100 medical specialties and sub-specialties.
Established in 1929, BJU International is published 12 times a year by Blackwell Publishing and edited by Professor John Fitzpatrick from University College Dublin, Ireland. It provides its international readership with invaluable practical information on all aspects of urology, including original and investigative articles and illustrated surgery. www.bjui.org