Comparison of sperm concentration in fresh and postal post-vasectomy semen samples: a prospective agreement study.

Abstract

Background: Most guidelines recommend post-vasectomy semen analysis (PVSA) on fresh samples to confirm success. Postal submission increases compliance although reliability remains controversial. We assessed agreement between first PVSA sperm concentrations on the same sample, freshly and following postage, and determined if any sperm concentration levels other than 'no sperm seen' on a postal sample could be used to advise cessation of other contraceptive methods.

Methods: 12 weeks after vasectomy, men submitted fresh semen samples to laboratory A. Samples were analysed within 2 hours. The remainder of each sample was posted to laboratory B for analysis 72 hours later. Both laboratories examined one aliquot of 25 µL using 100 µm CellVision counting chambers. Sperm counts for the entire slide were reported. No exact count was performed at concentrations estimated >100 000/mL.

Results: We analysed the results of 197 paired PVSA. The Bland-Altman plot showed high agreement between fresh and postal sperm concentrations, with only seven samples outlying 95% CIs. Fresh PVSA sperm concentrations were classified higher than postal in 47 (22.1%) pairs and lower in 42 (19.8%). Most discrepancies were observed at sperm concentrations <1000 sperm/mL. 'No sperm seen' was reported in 86 (43.7%) pairs with false negatives encountered in both laboratories (McNemar's test p=0.045). Negative predictive values of postal compared with fresh results were >99% at all cut-off values from 1000 to 100 000 sperm/mL CONCLUSION: Our study showed high agreement in sperm concentrations of first PVSA performed on the same samples submitted fresh or by postal submission. The current postal testing strategy could be modified to encompass clearance on postal PVSA showing very low sperm concentrations.