Matched to what? The U.S. is believed to have collected DNA samples from several of bin Laden's family members during the decade since the terrorist attacks of 9/11. According to an ABC News affiliate in Boston, one of those samples belonged to bin Laden's sister, who died of brain cancer about a year ago at Massachusetts General Hospital; after her death, government officials were reported to have taken some of her brain tissue for genetic testing.
Typical lab-based DNA matching tests like this can take up to 14 days; they're painstaking and need to be repeated several times to ensure the sample's not contaminated from any other DNA sources. But that's not necessarily the only way to do these tests: late in 2010, a University of Arizona team presented research on a machine that can do the analysis in just two hours in a largely automated way. It's possible that knowing they were engaged on a mission to capture bin Laden, U.S. forces arranged for access to a machine like this to be on quick alert — probably for flying blood, cheek cells, and other samples taken from the body to the lab for expedited analysis.