Testing of the cleaning efficacy and the cleaning-disinfecting efficacy of washer-disinfectors for thermolabile endoscopes (EWD) by using flexible endoscopes

Cleaning is of essential importance in the framework of reprocessing flexible endoscopes. Only properly cleaned endoscopes can be disinfected safely and
provide an adequate hygienic status assuring the safety of the next patient. Based on the instruction for reprocessing of the manufacturers of flexible endoscopes precleaning and manual cleaning need to be conducted prior to automated reprocessing in washer-disinfectors for flexible endoscopes (EWD). The requirements for the cleaning efficacy as well as for the complete process efficacy – as combined effect of cleaning and disinfection – of EWD have first been defined in ISO 15883-4 “Washer-Disinfectors: Requirements and tests for washer-disinfectors employing chemical disinfection for thermolabile endoscopes” in 2008 and extended in the revision of this standard in 2018. A method based on references [1] and [2] to evaluate whether the EWD meets the requirements defined in the above mentioned standard is described and hereafter modified for using flexible endoscopes itself as test pieces.

A1 Principle
Tests on cleaning efficacy [3] and complete process efficacy [4] should be performed using test pieces (PCD) first, followed by tests using surrogate channel systems as described in the revision of the ISO 15883-4:2018, Annex H [5], prior to using soiled flexible endoscopes as described hereafter. Only after having met acceptance criteria for cleaning and complete process efficacy using PCD and surrogate channel systems, subsequent tests with soiled endoscopes are performed. Selection of endoscopes should represent instruments of all relevant type test groups.
For testing the cleaning efficacy on flexible endoscopes, the instrument channel is soiled with reactivated sheep blood. Testing the complete process efficacy is done using reactivated sheep blood containing test organisms. The soiled endoscopes are loaded into the EWD to be tested. For the evaluation of the cleaning efficacy endoscopes are removed after the cleaning and the subsequent intermediate rinse.
For the evaluation of the complete process efficacy endoscopes are removed after the final rinsing but before the drying. The endoscopes are removed from the EWD, inspected for visual cleanliness – especially at the channel openings/valve openings – and subsequently tested for residual protein content by using the modified OPA-method (see C1.5.2) to assess cleaning efficacy or tested for reduction of test organisms (see C1.6) to assess the efficacy of the complete process.

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