Detachable distal cap duodenoscopes: a step in the right direction?

Over the past decade, numerous outbreaks of carbapenem-resistant enterobacteriaceae infections transmitted via duodenoscopes have been reported worldwide [1]. These outbreaks have identified a variety of potential etiologies for infection transmission, but a primary culprit has been the complexity of the elevator mechanism of duodenoscopes and the challenges of cleaning this element of the scope [2]. The initial US Food and Drug Administration (FDA) guidance involved performing enhanced reprocessing of duodenoscopes via one of four methods: “double” high-level disinfection (HLD), ethylene oxide sterilization, liquid chemical sterilization (via agents such as peracetic acid), or assessing the adequacy of HLD via microbial culturing of reprocessed devices. However, multiple subsequent studies (including randomized controlled trials) have questioned the benefit of these added steps [3] [4] [5]. Subsequently, an FDA post-market surveillance study identified potentially pathogenic bacteria on culture in up to 6 % of fully reprocessed duodenoscopes. These results led the FDA to recommend healthcare facilities to transition away from duodenoscopes with fixed distal caps [6]. These findings have also led manufacturers to develop disposable/detachable distal cap devices aimed at reducing the potential for transmission of infections via these devices. However, similarly to the enhanced reprocessing steps mentioned above, the magnitude of any potential benefit from such modifications remains to be determined.

“...this study is an important step forward, suggesting that the use of a detachable distal cap may reduce residual bacterial contamination or organic residue in duodenoscopes after high-level disinfection.”

In this issue of Endoscopy, Ridtitid et al. assessed the ability of a newly designed duodenoscope with a detachable distal cap (ED 580XT, Fujifilm, Tokyo, Japan) to reduce organic residue or bacterial contamination after standard HLD [7]. In this single-center study conducted over 5 months, 108 used duodenoscopes were assessed, of which half underwent manual cleaning with the distal cap attached while the other half had the distal cap removed to facilitate elevator cleaning. After HLD had been completed, samples were obtained from the elevator for culture and adenosine triphosphate (ATP) testing. While no pathogenic bacteria were isolated from either group, there was a significant reduction in median ATP relative light unit (RLU) values (45.2 vs. 141.0; P < 0.001) as well as the proportion of scopes with ATP RLU values of < 40 (20/54 [37.0 %] vs. 41/54 [75.9 %]; P < 0.001; relative risk ratio 0.49 [95 % confidence interval 0.33 – 0.71]) in the detachable cap group.

Of note, the post-HLD rates of bacterial contamination in this study were low and may be explained by a variety of factors. First, the scopes were relatively new and therefore may not have had the opportunity for significant wear and tear and the development of mechanical imperfections in the elevator tip. Second, it is unclear exactly how many of the new detachable cap duodenoscopes were in circulation and whether the two groups were created by randomization or another method. It is likely there were only a few of these new devices in use and that they comprised only a fraction of the total institutional fleet, given that it took 5 months to enroll 108 used devices for the study. One can then infer the possibility that a scope that was in the “fixed distal cap” group on one use could have been in the detachable distal cap group after a subsequent use. This allows for the potential of intermittently enhanced cleaning that could have lowered the observed rates of bacterial contamination. Third, albeit of unclear benefit, a significant proportion of the devices (61/108) underwent a second round of HLD given ATP RLU levels ≥ 40. Fourth, all control group devices appear to have undergone “a second cap-off cleansing based on the manufacturer’s reprocessing instructions” after culturing but before being reused, meaning each group ultimately received similar cleaning prior to the next reuse. Fifth, the instrument channels of the device were not sampled. Although the elevator appears to be the primary mechanism associated with infection transmission, defects and potential biofilm can certainly develop in the instrument channel. Finally, the study sample size was rather small given the anticipated 15 % difference in contamination rates between the groups and a larger study may have observed cases of bacterial contamination after HLD.

The study findings highlight two challenges of research involving duodenoscope reprocessing. The first is that the clinically relevant outcome, a device-transmitted infection, is (fortunately) exceedingly rare, making studies powered to assess this end point impractical. The second challenge is that while a practical surrogate marker of this outcome related to device contamination is needed, it has yet to be established. Most commonly, ATP testing or microbial culturing have been used for this purpose. However, these two markers have not correlated well with respect to assessing the adequacy of HLD. This author group has previously reported in abstract form that an ATP RLU < 40 has a 100 % sensitivity for subsequent bacterial culture positivity with a corresponding 100 % negative predictive value [8]. Of note, they suggest that this can be used as a valid point of care assessment of reprocessing adequacy. This is an important observation that needs to be validated via peer-review in future studies. Having a valid and rapid test to assess reprocessing adequacy is critical in establishing a “gold standard” that can be used to compare the efficacy of future interventions aimed at improving duodenoscope reprocessing. Ideally, this test would be simple, performed by one person, and relatively resistant to contamination/false positives.

In summary, this study is an important step forward, suggesting that the use of a detachable distal cap may reduce residual bacterial contamination or organic residue in duodenoscopes after HLD. Future studies, including post-market surveillance studies, should similarly assess duodenoscopes with disposable caps from other manufacturers as well as newer models with disposable elevator mechanisms. These studies should directly compare these devices against duodenoscopes with fixed distal caps. In addition, they should include sampling from the instrument channels to determine what level of contamination risk this region of the duodenoscope poses. This information will help to determine what added benefit, if any, a single-use device provides compared with devices that only replace the distal components of the duodenoscope. Obtaining accurate data regarding this information will be critical in allowing health care organizations to make sound economic decisions regarding modernization of their current fleet of duodenoscopes and in maximizing patient safety during endoscopic retrograde cholangiopancreatography procedures.

Publication History

Article published online:
26 August 2020

• References

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• 3 https://www.fda.gov/medical-devices/safety-communications/fda-recommending-transition-duodenoscopes-innovative-designs-enhance-safety-fda-safety-communication , accessed May 31, 2020
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