Dual use of Diff-Quik-like stains for the simultaneous evaluation of human sperm morphology and chromatin status

BACKGROUND: Sperm chromatin status and nuclear DNA damage can be detected using well-established assays. However, most techniques are time-consuming and/or involve elaborate protocols and equipment. We have recently developed a simple and fast method to monitor sperm chromatin status in field conditions using the Diff-Quik assay which is employed in fertility clinics to assess sperm morphology with standard bright field microscopy. In the present study, we demonstrate that any Diff-Quik-like stain can easily, reproducibly and routinely monitor human sperm chromatin status as well. METHODS: Different Diff-Quik-like stains were used to assess sperm morphology and the presence of abnormal dark nuclear staining in human sperm from four ART centres. The TUNEL assay was per-formed in the same samples, and fertility outcomes were assessed. RESULTS: A significant correlation was found between TUNEL-positive sperm and dark sperm nuclei. Moreover, associations were also found between the percen-tage of dark sperm nuclei and seminal parameters, embryo development rate, embryo quality and clinical pregnancy, as well as with cryptorchidism, and there was a tendency towards an association with age. A value of 32 % abnormal staining is suggested as a predictive threshold for embryo development and pregnancy. CONCLUSIONS: Our result