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This article was originally published in The Gray Sheet

Executive Summary

ENDOSCOPE INTERNAL COMPONENT CONTAMINATION STUDIES SHOULD BE CONDUCTED to determine the extent to which the interior parts of endoscopes remain contaminated with bacteria or virus after routine cleaning procedures, David Spach, MD, University of Washington, et al., conclude in a study published in the Jan. 14 Annals of Internal Medicine. The study declares that "despite appropriate cleaning and disinfection procedures," some endoscopes, because of their complex internal structure, remain contaminated, and "further studies should be done to evaluate the effectiveness of cleaning and disinfection procedures on the internal components." One study suggested by the authors would involve contaminating an endoscope then cleaning and disinfecting it. Subsequently, the device could be dismantled so that the internal channels and valves could be cultured. The conclusions in the study are based on a comprehensive literature review of articles related to the transmission of infections by flexible gastrointestinal endoscopes and bronchoscopes in order to determine common infecting microorganisms and "circumstances of transmission," as well as methods of risk reduction. In total, Spach et al. examined 265 articles published between January 1966 and July 1992. The reviewers found 281 infections and five deaths caused by insufficiently cleaned gastrointestinal endoscopes, and 96 infections and two deaths caused by bronchoscopes. Salmonella species and Pseudomonas aeruginosa were found to be the "most common" causative agents of infections transmitted by gastrointestinal microscopy, while mycobacterium tuberculosis, atypical mycobacteria, and P. aeruginosa were the most common causes of infections transmitted by bronchoscopy. Spach states, "overall...the number of reported infections is remarkably small, considering the millions of endoscopic procedures done annually, which...suggests a low incidence of infections transmitted by endoscopy." Spach asserts, however, that these reported cases "probably represent a minority of all infections transmitted by endoscopy, because they were primarily due to easily recognized bacterial infections characterized by short incubation periods and often occurring in large or unusual clusters." The study maintains that "low-level endemic transmission is almost certainly more difficult to detect and may be considerably underestimated" and "asymptomatic or brief self-limited illnesses would likely go unrecognized." Viral diseases with long incubation periods also would be hard to trace, as linking their transmission to a procedure done weeks or months before "is difficult." Also, he notes, "from the practitioner's perspective, the incentive for recognizing and reporting these infections is minimal." The study concludes that "large prospective studies should be conducted in which cultures are obtained from patients and patients are monitored for clinical disease after endoscopy." In addition, such studies should culture endoscopes and accessories to evaluate the compliance with cleaning and disinfection guidelines. In a conference on infection control and medical devices held in June 1992, FDA announced that it was developing a guidance document outlining requirements for reusable device labeling. This document would describe the information that should be included to allow for adequate device reprocessing between uses ("The Gray Sheet" July 6, p. 17). The document currently is in draft form. FDA's interest in creating a guidance was spurred in part by a study completed in March 1992 to "observe and assess the actual disinfection/sterilization of endoscopes." The study was conducted at 26 health care facilities in three states. A collaborative effort between FDA's device center and the state health departments of Iowa, Maryland and Massachusetts, the investigation found "actual disinfection/sterilization procedures for endoscopes are not always optimal...and high-level disinfection of gastrointestinal endoscopes is not always achieved" ("The Gray Sheet" March 23, p. 9). According to Spach, problems related to equipment design have played "an important role" in outbreaks of infections associated with the use of automated washers. Some of the problems include: "the difficulty in disassembling, cleaning and decontaminating the machine, the reuse of detergent, disinfection and tap water by the automated washer, and the presence of reservoirs that remain filled with fluid for extended periods of time." Spach states that "emphasis needs to be placed on manual cleaning before automated disinfection...and on frequent monitoring of the machines. Furthermore, the machines should be designed to ensure their resistance to internal contamination and...have an internal monitoring system...that automatically cancels the cycle when parameters are not acceptable." Spach also mentions that several manufacturers have "redesigned" the endoscope to enable a "verifiable system of disinfection," by creating a sterile sheathed endoscope. This device consists of a reusable endoscope without channels and a disposable sterile sheathed set that includes a sheath, air and water channels, a biopsy-sucking channel, a distal window, and a cover for the endoscope control body. Natick, Massachusetts-based Vision-Sciences already has received FDA clearance for use of its disposable Endosheath with a reusable flexible sigmoidoscope and is "planning to expand its offerings in gastrointestinal endoscopy" ("The Gray Sheet" Nov. 2, p. 14).

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