To the Editor—We appreciate the commentary by Whiteley et alReference Whiteley, Derry and Glasbey ¹ on our study in which several rapid indicators were used to detect residual contamination in gastrointestinal endoscopes following manual cleaning.Reference Visrodia, Ofstead, Yellin, Wetzler, Tosh and Baron ² The authors raise several concerns about an adenosine triphosphate (ATP) measuring device used in our study, including our use of a single commercially available ATP device, our reliance on only 1 ATP test per component sampled, possible variability in ATP results, and the inability of ATP monitors to identify specific microbes or quantify colony counts.Reference Whiteley, Derry and Glasbey ¹ Indeed, rapid indicator testing in endoscope reprocessing is a relatively new arena, and more research is undoubtedly needed to evaluate the utility of various devices and determine the association between residual organic debris, viable microbes, and patient outcomes.

Our study was a small pilot project designed to evaluate materials and methods that could be used to assess endoscope cleaning effectiveness. At that time, we sought to determine whether the recommended practice of visual inspection was an adequate standard for verifying whether manual cleaning had sufficiently removed residual contamination prior to exposing endoscopes to high-level disinfection. ^{3 ,} Reference Rutala and Weber ⁴ In addition to inspecting each component and the sampling materials for visually apparent evidence of residual contamination, our team conducted rapid indicator tests for blood, protein, and ATP. Multiple types of rapid indicators were used in order to assess various approaches for monitoring cleaning effectiveness and to compare their results. In summary, we foundReference Visrodia, Ofstead, Yellin, Wetzler, Tosh and Baron ² that endoscopes with and without visually apparent debris had levels of blood, protein, and ATP exceeding previously validated benchmarks.Reference Alfa, Fatima and Olson ^{5 ,} Reference Alfa, Degagne and Olson ⁶ Although high ATP levels may indicate the presence of viable microbes,Reference Hansen, Benner, Hilgenhoner, Leisebein, Brauksiepe and Popp ^{7 ,} Reference Fushimi, Takashina and Yoshikawa ⁸ such results could also reflect the presence of blood or other types of cells.Reference Turner, Daugherity, Altier and Maurer ⁹ Indeed, we found ATP levels were quite high in every sample that also tested positive for blood.

As noted by Whiteley et alReference Whiteley, Derry and Glasbey ¹ and acknowledged in the limitations section of our article, we did not include the performance of microbial cultures, because the goal was to evaluate multiple rapid indicators and sample collection methods. Furthermore, the value of conducting microbial cultures prior to high-level disinfection seems limited. In a subsequent study conducted by our team (as yet unpublished) we used microbial cultures as one of the indicators of endoscope reprocessing effectiveness.

The main goal of our study was to identify user-friendly materials and methods that could be used to evaluate manual cleaning effectiveness in the clinical setting. The chosen ATP monitoring system provided a numerical result reflecting the amount of ATP present. We found this to be superior to monitoring systems that measure residual protein or blood, which require users to interpret color changes on swabs or dipsticks.

Given the imperative for cost containment and to improve efficiencies on the front lines, we believe it would not be desirable to perform duplicate or triplicate testing as suggested by Whiteley et al.Reference Whiteley, Derry and Glasbey ¹ Their concern about variability within and between ATP measuring devices deserves additional study. However, we found that post–manual cleaning ATP and protein levels far exceeded benchmarks for manually cleaned endoscopes and perhaps are less likely to be affected by the degree of variability cited.

Quality assurance in endoscope reprocessing is needed, and rapid indicator testing is an area of growing interest and understanding. ATP testing offers potential, but given its relatively recent application to this field, additional research is necessary to better define its role.