ALBUMIN GRADIENTS DO NOT ENRICH Y-BEARING HUMAN SPERMATOZOA

The aim of this study was to evaluate objectively whether or not disco ntinuous albumin gradients enrich the proportion of Y-bearing human sp erm, A blinded, collaborative trial design was employed whereby a lice nsed centre prepared the sperm fractions using licensed procedures, co ded the sperm slides and then sent them to an independent laboratory f or determination of the X:Y ratio in each sperm fraction using X and Y chromosome-specific probes and double label fluorescence in-situ hybr idization (FISH), The identification codes and FISH results were colla ted by an independent third observer, Two albumin gradient methods whi ch are currently used by licensed centres for male sex pre-selection? protocol 3 and modified protocol 3, were tested, Essentially the same results were obtained for the two methods, Highly motile sperm fractio ns were recovered from the albumin gradients, and the recoveries of mo tile spermatozoa (1.3-8.5%) were within the optimal range reported to produce maximal enrichment of Y-bearing spermatozoa. FISH analysis, ho wever, revealed no enrichment for Y-bearing spermatozoa with either me thod, and the overall X:Y ratios were not significantly different from 1.0, Some samples showed marginal enrichment of Y-bearing spermaotozo a, whereas others showed marginal enrichment of X-bearing spermaotozoa . In conclusion this collaborative study has demonstrated that the pro tocol 3 and modified protocol 3 albumin gradient procedures do not enr ich Y-bearing spermatozoa, The clinical use of albumin gradients for m ale sea preselection should be reconsidered in the light of this and o ther evidence.