Assessing sperm chromatin and DNA damage: clinical importance and development of standards.

Over the past 20 years, numerous new methods have been developed to identify changes in the organization and composition of sperm chromatin as well as to determine the extent of DNA damage in the nuclei of spermatozoa. Although these methods are being used effectively in assessing how toxicants act on sperm chromatin quality in agricultural settings, their use as complementary biomarkers of sperm quality in assessing male fertility remains controversial. We review some key aspects of the assessment of sperm chromatin quality and DNA damage and identify some of the most widely used tests to monitor these endpoints. An approach to validate three tests by standardizing methodology and determining interlaboratory variation for each test using a standard set of samples is outlined.