Diagnostic accuracy of an initial azoospermic reading compared with results of post-centrifugation semen analysis...

Semen analysis is a common laboratory procedure but few data are available to support recommendations as to whether centrifugation is necessary in the post-vasectomy context. We evaluated the accuracy of a pre-centrifugation determination of azoospermia compared with post-centrifugation results.

We conducted a secondary analysis of data from 3,205 semen analyses performed during a randomized clinical trial of 2 vasectomy techniques--ligation and excision with fascial interposition vs ligation and excision without fascial interposition. We performed brief, initial microscopic examinations to categorize sperm numbers per high power field to decide whether centrifugation or dilution was needed before estimation of sperm concentration. For specimens initially categorized as azoospermic, we reviewed the post-centrifugation semen analysis results to estimate the accuracy of the initial finding.

Of 2,104 samples categorized as azoospermic before centrifugation, post-centrifugation analysis demonstrated that all but 4 (99.8%) were azoospermic or had a sperm concentration of less than 100,000 sperm per ml. Four samples from 1 study site had counts between 104,000 and 315,000 sperm per ml. Of 1,610 apparently azoospermic samples obtained at 10 weeks or later after vasectomy there were 12 (0.7%) that had some motile sperm identified after centrifugation but the numbers of motile sperm were low (mean 1,124 motile sperm per ml, range 238 to 3,710).

Microscopic examination of uncentrifuged specimens is a reliable method for identifying semen samples after vasectomy with more than 100,000 sperm per ml.