Three months after deadly superbug outbreaks sparked alarm nationwide, U.S. hospitals are still searching for how best to clean a controversial medical scope and keep patients safe. Federal regulators have declined to pull the difficult-to-clean duodenoscopes off the market, and there's no indication that manufacturers can quickly redesign the reusable devices, which are employed in nearly 700,000 procedures annually. Absent clear guidance from health officials, hospitals are resorting to a wide variety of cleaning and testing approaches — including some that remain unproven. Doctors and hospitals are hoping to get more answers Thursday and Friday from a federal advisory panel that's being asked to recommend ways to ensure patient safety during ERCP, or endoscopic retrograde cholangiopancreatography.