How reliable is Political Hotwire? There's nothing quoted there in which Dr. Carson refutes the possibility that the child is his, just that he doesn't trust the DNA testing (pretty strange attitude for a doctor). His "he doesn't trust gov testing" doesn't sound any more true than a lot of stuff he says, since he could get second tests if he doubted the results.
I don't know who Dr. Carson really is any more than I know who Obama really is.