Study examines ideal surface damage testing protocol

All manufacturers of healthcare patient care equipment should provide instructions for use (IFU) that list compatible disinfectants for cleaning equipment. However, compatibility testing is not standardised across the industry, does not use validated methods, does not generally include newer disinfectant technologies, often is only qualitative, and may only list active ingredients which does not take into account the other ingredients in a disinfectant that may cause surface damage. This makes it challenging to compare surface damage information among disinfectant manufacturers and equipment manufacturers.

In some cases, equipment manufacturers list ingredients not compatible with their equipment in the IFU, yet recommend disinfectants including the same ingredients, resulting in confusion for healthcare facilities to evaluate and choose disinfectant products.

It is difficult to predict the clinical impact of surface damage because there is no clear definition of what constitutes surface damage. In theory, surface damage can cause equipment to fail to operate correctly and can shelter microorganisms, thus preventing proper disinfection. Both types of surface damage can create safety risks for patients and staff in healthcare facilities.

Surface damage can be defined as a quantifiable physical or chemical change from the original manufactured state of an object (surface or device). Surface damage that results in aesthetic changes, such as colour loss or change in colour, may not affect the performance of the equipment and thus may not be of any clinical significance.

We recommend using surface roughness as an appropriate parameter to determine surface damage. Changes in surface roughness can indicate a loss of material from the surface, an increase in the number of cracks or fissures, or irreversible changes in the chemical bonding in organic surface materials, which can change the performance of the surface.

The link between surface roughness and microbial risks has been explored by previous studies. Verran and Boyd¹ reviewed data showing that surface roughness can create defects in the surface that provide protection from shear forces, such as from cleaning, and may provide more secure adhesion points for bacteria. Aykent,² from the field of dental finishing, showed that the amount of bacteria on a surface was positively correlated with the surface roughness. Gonzalez³ showed that rougher surfaces were harder to clean of blood soil, but did not quantify the degree of surface roughness necessary to see this difference. Notably, the size scale of the change in surface roughness is often below the detection limit of humans via sight or touch.

Surface damage can make it more difficult to disinfect a surface or create some other definable safety risks (such as surface damage exposing wiring or cracking tubing), both of which have clinical significance. When surface damage is minor, it may be detectable, but not have achieved any clinical significance. However, if the surface damage continues, it may reach a point of clinical significance at some later time. Even minor surface damage should be considered important because of the potential for surface damage to reach the threshold point. Therefore, surface roughness, which is related to the ability to disinfect the surface, is an appropriate parameter to address the question of proper disinfection to avoid surface damage, although what constitutes significant damage remains undetermined at this point.⁴

Surface damage measurement

Ideally, a detector should be placed on a surface in question, and by pressing a button, quantitative data would be generated that would compare the original condition of the surface to the changes in the surface over time. Using a database of information tested using this method, it would be possible to quantify the amount of additional risk associated with the degree of damage. However, no such device or database exists today.

The field of materials science has worked extensively on methods to characterise surfaces. What makes this characterisation valuable is the ability to tie the characterisation method to a specific parameter (or parameters) that allow for differentiation among surfaces in a meaningful manner. It is unlikely that a single test would allow for a relevant determination of surface damage. It would either be too sensitive, identifying surfaces as damaged that do not have clinically relevant damage, or conversely, it would only identify surface damage when it was so extreme that the surface could no longer be used. It is important to address this concern, as it relates to healthcare surfaces and the disinfectants and wiping cloths used on them.

Proposed sample preparation method

Based on the evaluation criteria discussed above, we believe that applying the disinfectant through wiping and allowing the surface to air dry is an appropriate methodology.

A four-pass wiping method (left, right, left, right) would provide adequate contact between the surface and the disinfectant chemical and factor in the wiping cloth impact as well, and is consistent with the current EPA wipes test method.

The surface should be allowed to air dry for a defined period of time, such as 10 minutes, before reapplication of the product.

This process should be repeated 200 times to simulate the damage that could occur by disinfecting the surface daily for six months. Other numbers of repetition may be just as predictive of surface damage, but 200 cycles should be representative of any likely damage due to normal use.

Surfaces roughly two inches wide by 12 inches long would be appropriate during this sample preparation. The sample after disinfection wiping can be cut into appropriate pieces for testing. All testing should be run in triplicate.

It may be desirable to additionally test samples immersed in disinfectant chemicals for a period of time but this would only be done as part of overtesting and would not replace the standard wiping method of application. Immersion, while not reflective of the type of exposure for surfaces from normal use of disinfectants, can provide an indicator of what surface damage a worst-case exposure might be expected to cause.

If standard wiping and immersion both do not show any significant surface damage, then this provides strong evidence that the disinfectant/surface combination is not likely to cause surface damage under normal use or under extreme exposure conditions.

To view the full paper, visit http://www.diverseyvericlean.com/images/DiverseyHumming/Coronavirus/63313_LIT_Surface_Damage_Article_A4-en_LR.pdf.

References

1. Verran J, Boyd RD, “The relationship between substratumsurface roughness and microbiological and organic soiling: A review”, Biofouling, 2001; 17 (1): 59-71.
2. Aykent F, Yondem I, Ozyesil AG, Gunal SK, Avunduk MC, Ozkan S, “Effect of different finishing techniques forrestorative materials on surface roughness and bacterial adhesion”, J of Prosthet Dent, 2010; 103: 221-227.
3. Gonzalez EA, Nandy P, Lucas AD, Hitchins VM, “Designing for cleanability: The effects of material, surface roughness, and the presence of blood test soil and bacteria on devices”, Am J of Infect Control, 2017; 45: 194-196.
4. Sattar SA, Maillard JY, “The crucial role of wiping in decontamination of high-touch environmental surfaces: Review of current status and directions for the future”, Am J Infect Cont, 2013; 41: S97-S104.

Peter Teska (MBA), Jim Gauthier (CIC), Kay Bixler and Xiaobao Li (PhD) are from Diversey, Inc.; John Howarter (PhD) and Haley Oliver (PhD) are from Purdue University.