[Influence of the analytical process in the appearance and disappearance of the spermatozoa after vasectomy]

To evaluate if the analytical process might justify that in some patients rare non motile sperm might be seen in some but not all their post-vasectomy semen samples.

Post vasectomy ejaculates received in our Center from january 2002 to december 2004 were reviewed. We used our own guidelines for post vasectomy semen assessment based upon those of the British Andrology Society for the evaluation of post vasectomy semen samples and the World Health Organization guidelines for semen analysis.

During the 3 years of follow up, 984 patients underwent vasectomy. We received 1.430 semen samples, 2 samples per patient on average. Regarding the pre analytical phase, 134 samples (9.4%) were not completely collected; ejaculate volumes of less than 2 mL were delivered by 269 patients (18.8%); in these cases, we were not sure whether the whole ejaculates were submitted: pre analytical conditions of 11 samples (0.8%) were inappropriate: incorrectly labeled, spilled, provided into inadequate containers... Regarding the analytical phase, 432 ejaculates (30.5%) were extremely viscous and sperm detection might have been affected; 62 semen samples (4.3%) contained many cells which obstructed the visualization of the entire microscopy field. Regarding the post analytical phase, 153 patients (20.9%) had alternative negative/positive results with rare non motile sperm.

An elevated percentage of incidences involving both the pre analytical and the analytical phase were observed during post-vasectomy seminal analysis. Inadequate conditions may affect the results and justify that spermatozoa may be seen in some but not all the ejaculates of the same patient. We recommend that two semen samples per patient are required to ensure that he is correctly evaluated. We propose to report a negative result as a spermatozoa count bellow the detection limit of our analytical procedure similar to other laboratory magnitudes to minimize the effect of fluctuations in such a low count of rare non motile sperm.