In this case, the result might be hugely misleading as haemoglobin, unlike other proteins in the blood and other soft tissues, dissolves well in water. With enough time, haemoglobin dissolves and disappears from the token, even if water alone is used. What makes the problem much worse is that the remaining proteins not only stick to the surfaces firmly but are often translucent and so they are very difficult to see by the naked eye.

The 360-degree approach Most PCDs for cleaning simplify the complexity of many surgical instruments to a flat piece of material with a test soil on it. To simulate the complexity of surgical instruments, some PCDs use holders that artificially recreate challenges of narrow gaps or partial shadowing – in most cases, instruments are simplified to one surface only. This approach is problematic since spatial orientation, especially in case of automated washing, is critical since the mechanical force of jets from spray arms or even in ultrasonic washers, albeit to a smaller degree, is not distributed equally in all directions. In reality, all instruments are three dimensional, and all need to be clean everywhere – therefore, PCDs should reflect this as well.

Case study: what looks clean and is in fact not

This study was carried out as a part of the evaluation of a new range of cleaning chemicals. The first stages of the process were looking at optimisation of the process to find the cycle parameters that would clean the tags such that no proteins are detected by the protein detection dye, VeriTest Blue.

VeriTest PCDs use a natural blend of blood and homogenised tissue to represent real contamination accurately. Critically, they are composed of a mixture of water-soluble and insoluble proteins that replicate the behaviour of patients’ blood and tissue on instruments after surgery.

VeriTest AW Tags were selected as the reference tool for the study. They were loaded to a VeriTest Multi Basic block that evaluates four different surfaces at the same time (top, bottom, side and shadowing). The blood and tissue homogenate soil was selected to reflect the complex composition of the contamination on surgical instruments. VeriTest AW was developed specifically to test automated washers after instruments. Additionally, this natural test soil allows the evaluation of cleaning performance with protein detection systems. During the study, a PCD was placed in Aseptium’s Laboratory Washer Disinfector on a bespoke rack that made sure the location of the block was the same for each iteration of cycle parameters. This washer was selected for the study as its spray arms were developed to provide consistent cleaning performance, ensuring the load is cleaned all-around, from all directions. Using Aseptium’s Matrix approach for process optimisation,1

the following parameters were

proven to deliver best results. Results were analysed using protein detecting dye that

Water control cycle As a part of the study, we wanted to find out how the PCD would behave when no chemical was added to the process, in order to evaluate whether the PCD would detect a process without chemicals. Picture 3 shows the results of that process with the following cycle parameters: l Initial rinse: 2min at 25˚C l Wash: - Stage 1: 5min at 42˚C - Stage 2: 5min at 55˚C

Picture 2. Clean VeriTest PCDs after an optimised cycle and verified with VeriTest Blue.

l Rinse 1: 1min at 25˚C l Rinse 2: 1min at 25˚C

Picture 3. VeriTest AW tags after the process – magnification 2x. Dry tags left, VeriTest Blue dye right.


In Picture 3, dry tags show traces of contamination, but only when observed under direct light. The change in light reflection from the surface can poentially highlight the area where proteins have adhered to the surface. However, without checking for reflections, it was very difficult – if not impossible – to see any contamination, as this layer of residual proteins is translucent. VeriTest Blue dye confirms the case and the outlines of the contaminated area are clearly highlighted in blue. The shape of the tags and the area covered by


binds to proteins and dyes them blue (Picture 2). VeriTest Blue saturates after around 30 min, so all pictures in the study were taken after 30 min exposure to the protein detection dye.

A clean result with chemicals The following represents the cycle profile used in Picture 2: l Initial rinse: 2min at 25˚C l Wash: - Stage 1: 5min at 42˚C - Stage 2: 5min at 55˚C

l Detergent was dosed at 35˚C at a concentration of 4ml/l

l Rinse 1: 1min at 25˚C l Rinse 2: 1min at 25˚C

All VeriTest AW tags used are visually clean. Visual inspection was carried under a spotlight, and results were verified with VeriTest Blue protein detection dye. No blue discolouration was noticed.

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