Smart kid, but he had to learn to slow down. "Listen Son, I know your fast but sometimes you've got to take your foot off the gas. Your identity is one of your most important assets. Don't be exposed just because someone saw you use your speed when you could have taken three steps."
Barry took the swab from the boy, sealing it in a sterile container. He took a sample from his own cheek and repeated the trick. With both containers labelled, he deliberately slowly walked over to the computer and sent an email to his superiors explaining he wasn't feeling well and was heading home to recover. He didn't particularly like lying, but Bart's appearance made getting to the bottom of this mystery much more important.
"We're not going to test them here, I'm too close to it all." Ever the scientist, he was eliminating variables. "We're going to ask Batman. Do you know the way to Gotham?"