Siblings Size-up Margins of Safety

Bob and Sarah worked together again (see the announcement of our first collaboration here) on a post over at Medical Law Perspectives: Uncleanable ERCP Duodenoscopes: Manufacturer, Hospital, and Physician Liability?  This time, Bob clarified the comparison of two margins of safety. 

In an editorial published in JAMA last October, William A. Rutala, PhD, MPH, Professor of Medicine, University of North Carolina School of Medicine, Chapel Hill; Director, North Carolina Program for Infection Control and Epidemiology; Director, Hospital Epidemiology, Occupational Health and Safety Program Hospital Epidemiology, University of North Carolina Health Care; and David J. Weber, MD, MPH, Professor of Medicine, Division of Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, stated that the margin of safety associated with cleaning and high-level disinfection of gastrointestinal endoscopes is 0-2 log10. Rutala WA, Weber DJ. Gastrointestinal endoscopes: a need to shift from disinfection to sterilization? JAMA. 2014 Oct 8;312(14):1405-6. PMID: 25291575. Rutala and Weber compared this low margin of safety to the 17 log10 margin of safety associated with cleaning and sterilization of surgical instruments. 

But I had no idea how 2 log10 compared to 17log10. Bob explained that, at best, the margin of safety of endoscope reprocessing is 15 to 17 orders of magnitude less than the margin of safety for reprocessing of surgical instruments. Not 15 to 17 times less. 15 to 17 orders of magnitude less. That is literally over a quadrillion times less. So, the margin of safety associated with the cleaning protocol for duodenoscopes recommended in instructions provided by the manufacturer (Olympus Corporation) and the FDA is over a quadrillion times less than the margin of safety for reprocessing surgical instruments.