Post-thaw recovery of rare or very low concentrations of cryopreserved human sperm.

OBJECTIVE To analyze cases in which no sperm could be identified after thawing among cryopreserved samples of rare or very low concentrations of sperm. DESIGN Retrospective, single-institution, cross-sectional. SETTING Male infertility clinic. PATIENT(S) We identified couples that underwent intracytoplasmic sperm injection (ICSI) with the use of either ejaculated or testicular cryopreserved-thawed sperm. Inclusion criteria were men with <100,000 total ejaculated sperm or men with azoospermia due to spermatogenic dysfunction who underwent microsurgical testicular sperm extraction with similarly low pre-cryopreservation sperm counts. Pre-cryopreservation specimens were categorized as "rare sperm only" (Group 1) or <100,000 total sperm (group 2). "Rare sperm only" applied to cases in which only one to three sperm were identified in a search of >20 high-power fields. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Cases in which no sperm were able to be found post-thaw (i.e., complete cellular loss) for use at the time of a programmed IVF cycle. RESULT(S) We analyzed 55 men (83 ICSI cycles). There were five ICSI cycles (6.0%) among five different couples in which no sperm could be identified post-thaw. Of these, four cases were from group 1 (8.5%) and one from group 2 (2.8%). Complete cellular loss occurred in 5.8% of testicular sperm samples and 7.1% of ejaculated sperm samples. There were no statistical associations between the ability to locate sperm post-thaw and the pre-cryopreservation parameters or sperm source. CONCLUSION(S) Failure to retrieve any sperm after thawing of rare or very low concentrations of cryopreserved sperm is an infrequent event and largely limited to those patients with rare quantities of sperm.