Leaving threatened range with Opportunistic Withdrawal


The Opportunistic Withdrawal feat from D&D 4e PHB3 says:

While you are adjacent to an enemy granting combat advantage to you your movement doesn’t provoke opportunity Attacks from that enemy.

If an enemy grants me advantage, does Opportunistic Withdrawal allow me to move out of the threatened area without suffering OA? An OA is an immediate interruption so technically I’m still adjacent, so how does it work in this case?