What is measured
The test reports two values: the DNA Fragmentation Index (DFI) is the percentage of sperm with detectable DNA damage, and High DNA Stainability (HDS) is the percentage of sperm with immature chromatin.
How the test works
The method follows the sperm chromatin structure assay (SCSA) principle. Sperm are briefly exposed to acid, which converts fragmented DNA to single strands while intact DNA stays double-stranded. They are then stained with acridine orange. Under 488 nm laser light in a flow cytometer, acridine orange bound to double-stranded DNA fluoresces green (515 to 530 nm) and bound to single-stranded DNA fluoresces red (630 to 650 nm). The ratio of red to total (red plus green) fluorescence, measured in at least 5,000 sperm, is used to calculate the DFI.
When it is requested
The instructions for use list unexplained infertility; persistent infertility even after treatment of the female partner; couples considering IUI, IVF or ICSI; recurrent miscarriage or early pregnancy loss; men over 40, men who smoke, or men taking certain prescription medicines that can affect sperm; men treated for cancer, exposed to toxic agents or who have had a urinary tract infection; and men considering varicocele repair.
Samples and handling
Fresh semen is transported at 37 °C and processed within five hours. A sperm preservation reagent allows storage at 2 to 8 °C for up to 72 hours, at −20 °C for up to seven days or at −80 °C for up to 30 days, without liquid nitrogen.