McMartin C, Lehouillier P, Cloutier J et al: Can a low sperm concentration without assessing motility confirm vasectomy success? A retrospective descriptive study. J Urol 2021; 206: 109.

The American Urological Association (AUA) recommends that vasectomized men be considered sterile when a first fresh, noncentrifuged semen analysis done 8 to 16 weeks after the vasectomy shows 100,000 nonmotile sperm/ml or less.¹ The presence of motile sperm at this time indicates a failure of occlusion of the vas deferens due to a surgical error or, most frequently, to a recanalization.^2,3

To assess sperm motility, men must provide their sample at an appointment site typically no later than 1 hour after ejaculation.¹ The inconvenience of producing a fresh sample (including time constraints, distance, busy schedule, embarrassment) is the main reason why many men do not comply with the post-vasectomy semen analysis (PVSA).^4–7 In North America, only about two-thirds of men have at least 1 PVSA.¹

Two alternatives to PVSA exist that may increase compliance by reducing the barriers associated with producing a fresh sample. However, they do not assess sperm motility. First, vasectomized men can send their semen sample by mail. Men can then stop using other methods of contraception only if the PVSA shows no sperm.¹ Second, men can use SpermCheck® Vasectomy, a home qualitative immunodiagnostic test. The test evaluates if the sperm count is either below or above 250,000/ml, indicating the success or failure of the vasectomy, respectively.⁸

A sperm concentration under which motile sperm are never or very rarely observed after vasectomy could decrease the need for additional testing in men who provide their sample by mail. It could also support the use of SpermCheck® Vasectomy as an alternative to increase compliance with PVSA.⁵ The objective of our study was to determine the probability of observing motile sperm according to sperm concentration in a large number of PVSAs performed on fresh sperm specimens.

We conducted an observational retrospective study of PVSA performed at the andrology laboratory of the Centre hospitalier universitaire de Québec-Université Laval, Quebec City, Canada between May 2016 and November 2019. Sperm concentration and motility were assessed on fresh noncentrifuged 10 μL samples at 400× magnification. An anonymized database of the PVSA reports was created for analysis. We calculated the proportion and 95% confidence interval of PVSA showing motile sperm according to sperm concentration for all prescribed PVSAs by any physician and limited to the first PVSA prescribed by the physicians who performed the most vasectomies (identified as vasectomists thereafter).

We identified 6,492 PVSAs prescribed by 169 physicians. The 5 vasectomists prescribed 95.6% (6,204) of the PVSAs, from which 96.1% (5,965) were first tests; 68.9% (4,108) were performed between 8 and 16 weeks after the vasectomy, as recommended by the AUA.¹ Vasectomy occlusion technique was performed with mucosal cautery and fascial interposition in at least 93.7% (6,080/6,492) of the PVSAs.

Figure. Proportion of post-vasectomy semen analysis (PVSA) results with motile sperm according to sperm concentration.

Motile sperm were observed in 150 (2.3%, including and 6.2% excluding the “None observed” category) of all PVSAs and in 103 (1.7% and 4.8%, respectively) of the first PVSA prescribed by the 5 vasectomists. In this last group of first PVSA, 95.7% (5,708) met the 100,000 nonmotile sperm/ml vasectomy success criteria recommended by the AUA.¹

Motile sperm were present at all sperm concentration strata in both groups of PVSAs analyzed (see figure). The proportion of PVSAs with motile sperm was, however, very small at lower sperm concentrations. Among men who had a first PVSA prescribed by one of the 5 vasectomists, only 17 (0.9%) of the 1,917 men with a sperm concentration between 100 and 100,000 sperm/ml and 19 (1.0%) of the 1,952 with a sperm concentration between 100 and 250,000 sperm/ml had motile sperm. Including the “None observed” category in the denominator, the proportion of men with motile sperm at their first PVSA decreased to 0.3% among both the 5,725 men with less than 100,000 sperm/ml and the 5,760 with less than 250,000 sperm/ml. The proportion of PVSAs with motile sperm increased with larger sperm concentrations, reaching very high proportions at sperm concentrations of 1 million sperm/ml or more (see figure).

To our knowledge, this is the first study to estimate the probability of observing motile sperm after vasectomy stratified by sperm concentration. It showed that motile sperm are present in all sperm concentration strata after vasectomy. However, the probability of observing motile sperm ranges from very small at lower sperm concentrations to very high at large sperm concentrations.

Our results have important clinical implications. First, although a fresh sample is usually recommended for additional PVSAs,^1,9,10 if the first PVSA on a mailed sample shows less than 1 million sperm/ml, we recommend requesting additional samples by mail. With higher sperm concentrations in the first PVSA, submitting a fresh sample makes more sense, however, as the risk of recanalization is much higher. Second, we observed that the probability of missing motile sperm with a first negative SpermCheck Vasectomy home-based test result would be very low (0.3%). The risk of falsely concluding a vasectomy was a success with 2 consecutive negative test results, as recommended by the manufacturer, is minimal.

In conclusion, the very low probability of falsely concluding that a vasectomy was a success at low sperm concentrations when the vas deferens was occluded with thermal mucosal cautery and fascial interposition supports the use of mailed sperm sample and home-based test. The optimal PVSA strategy for the patient must, however, involve shared decision making, balancing the inconvenience of providing a fresh sample with the risk of a false negative result.¹¹