Simulated-use validation of a sponge ATP method for determining the adequacy of manual cleaning of endoscope channels

BACKGROUND: The objective of this study was to validate the relative light unit (RLU) cut-off of adequate cleaning of flexible colonoscopes for an ATP (adenosine tri-phosphate) test kit that used a sponge channel collection method. METHODS: This was a simulated-use study. The instrument channel segment of a flexible colonoscope was soiled with ATS (artificial test soil) containing approximately 8 Log(10)Enterococcus faecalis and Pseudomonas aeruginosa/mL. Full cleaning, partial cleaning and no cleaning were evaluated for ATP, protein and bacterial residuals. Channel samples were collected using a sponge device to assess residual RLUs. Parallel colonoscopes inoculated and cleaned in the same manner were sampled using the flush method to quantitatively assess protein and bacterial residuals. The protein and viable count benchmarks for adequate cleaning were <6.4 ug/cm(2) and <4 Log(10) cfu/cm(2). RESULTS: The negative controls for the instrument channel, over the course of the study remained low with on average 14 RLUs, 0.04 ug/cm(2) protein and 0.025 Log(10) cfu/cm(2). Partial cleaning resulted in an average of 6601 RLUs, 3.99 ug/cm(2), 5.25 Log(10) cfu/cm(2)E. faecalis and 4.48 Log(10) cfu/cm(2)P. aeruginosa. After full cleaning, the average RLU was 29 (range 7–71 RLUs) and the average protein, E. faecalis and P. aeruginosa residuals were 0.23 ug/cm(2), 0.79 and 1.61 Log(10) cfu/cm(2), respectively. CONCLUSIONS: The validated cut-off for acceptable manual cleaning was set at ≤100 RLUs for the sponge collected channel ATP test kit.