Inter-and Intra-Laboratory Standardization of TUNEL Assay for Assessment of Sperm DNA Fragmentation

The functional aspects of sperm activity such as sperm chromatin integrity and ability to fertilize cannot be characterized by routine semen parameters. Men with unexplained infertility and idiopathic infertility, as well as men with normozoospermic semen profiles, show high DNA fragmentation. Molecular anomalies in the sperm can be detected by a sperm DNA fragmentation (SDF) assay which can be used in adjunct to conventional semen analysis. While the sperm chromatin structure assay (SCSA) remains the "gold standard," the TUNEL assay using flow cytometry is becoming popular among the different tests that are currently available to measure sperm DNA fragmentation. In this unit, we describe the inter-laboratory and intra-laboratory standardization of the TUNEL assay using a benchtop cytometer. The article also provides a step-by-step protocol for measuring sperm DNA fragmentation using the TUNEL assay and a bench-top flow cytometer, and also points out the inherent challenges with this test. © 2017 by John Wiley & Sons, Inc.