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A1) It is the ProReveal test protocol to rewash any instrument that has been sprayed and tested. Tests have shown that after rewashing the level of fluorescent residual proteins potentially still present is negligible and will be well below acceptable limits.
A2) Toxicology data and Health and Safety information is available. To find out more how the product works call Synoptics Health to arrange an on-site presentation. The fluorescent spray has a PH of only 9.2. Instrument manufacturers recommed using chemistries below a PH of 10 in their reprocessing instructions. The reagent doesn't contain any chemistry that is not compatible with all types of surgical instruments. Instruments are rewashed after testing in a validated washer disinfector, so the patients will not come into contact with any residue spray.
A3) ProReveal is detecting residual protein left on an instrument after washing. ATP of course is not a protein but a purine nucleotide.
A4) The ProReveal system can be set to a detection level which is agreed either at a local level or any level set by regional or national health authorities. The user has full control over the setting of this level.
A5) The simple answer is no. A common perception is that the sterilisation process makes an instrument safe to re-use. However, research has shown that relying on autoclaving at 121 degrees C for prion decontamination could be unsafe.
Jackson et al., determined that ‘prions are highly resistant to conventional chemical and physical procedures designed to inactivate viruses and bacteria, including treatment with organic solvents, formaldehyde and detergents and sterilisation at 121 degrees C’. Clink here to link to Paper. It is therefore important that due to the highly resistant nature of prions, that a test such as ProReveal is used to check the effectiveness of the washer disinfection process which is performed after the washing step but before sterilisation.
From recent testing with the ProReveal, two instruments were tested to determine whether any residual protein was present or not. The first instrument tested was a Cuscoe Speculum which had been washed, packed and sterilised by steam Autoclave in a SSD. The ProReveal clearly shows that significant amounts of residual protein are present on the instrument even after sterilisation, hence can remain a major source of contamination. (Figure 1).
Figure 1 - ProReveal image of a Cuscoe Speculum after sterilisation
The yellow and red areas show the presence of residual protein
The second instrument tested was a pair of Tissue scissors supplied as pre-sterile from a manufacturer. The ProReveal again showed that residual protein is present on the scissors which are considered to be new and unused. (Figure 2).
Figure 2 - ProReveal image of Tissue scissors supplied pre-sterile
The yellow and red areas show that residual protein is present
The conclusion we draw from this is that SSD departments should not rely on the effectiveness of their washer disinfection process (including sterilisation) without having some sort of check process like ProReveal in place.
Q6) I use ninhydrin to check my instruments after the washer disinfection process. Is this the best test to use?
A6) Ninhydrin has been used for many years in SSDs and it has been widely thought to be a suitable test for detecting protein. However, from recent research it has been determined that ninhydrin does not provide sensitive detection of proteins and can generate high numbers of false negatives when used in decontamination practices.
Nayuni et al., have shown that ‘ninhydrin kits, currently used in SSDs, are infective at detecting residual proteins due not only to the insensitivity of ninhydrin towards proteins but also to the poor desorption of adhered proteins by swabbing’.
Figure 1 - Protein detection using a commercial ninhydrin kit
BSA (10-1000 microgram) was pipetted into each tube in a Browne ninhydrin protein detection kit. The tubes plus the supported positive and negative controls were incubated according to the manufacturer’s instructions. The commercial kit gave no coloration even with 1000 microgram BSA pipetted directly into the supplied reaction vials whereas the positive control arginine (amino acid) gave an intense purple colour (Nayuni et al, 2012).
Q7) ContaminationLimit is given as SignalMass (µg) – can this be changed?
A7) Yes this can be changed on the setting tab by selecting ’Configure Contamination Limit’.
Q8) ContaminationLimitValue is set at 2, is pass/fail purely based on whether ContaminationMeasurement is above or below 2?
A8) Yes if the value is below 2, it will pass and if it is above 2, it will fail.
Q9) Is ContaminationMeasurement exactly the same as SignalMass (µg) for every report and if so why have 2 descriptions?
A9) The ContaminationMeasurement is the value measured to test against the contamination limit, so the actual value will depend on the algorithm configured for the contamination limit settings – so not always the same as SignalMass.
Q10) What is the difference between SpecimenArea (mm²) and SignalArea (mm²), and what is the significance of the SignalAreaPerSpecimenArea (mm²/mm²) figure?
A10) In all cases: “Specimen” refers to the whole region within the boundary of the surgical instrument, “Signal” refers to detected contamination.
Therefore, the SpecimenArea is the size calculated for the surgical instrument and the SignalArea is the size covered by contamination.
The SignalAreaPerSpecimenArea can be interpreted as the fraction of the whole surgical instrument surface which is contaminated.
Q11) SignalMassPerSpecimenArea (µg/mm²) and SignalMassPerSignalArea (µg/mm²) are calculated so could one of these be used to assess Pass/Fail instead of SignalMass (µg) which would seem to take no account of the size of the device?
A11) Yes, SignalMassPerSpecimenArea (contamination per unit area of surgical instrument) or SignalMassPerSignalArea (density of contamination) can be configured as a contamination limit.
Q12) Can the pass/fail decision be based on contamination detected on areas of the device which contact patient tissue rather than the total or average per mm² on the device generally e.g. by defining a certain area of the device to analyse?
A12) The ProReveal unit is normally intended to test an object which has been through the washing process rather than to test specific parts of individual surgical instruments. There is no way to identify significant parts of the sample under test.
Q13) How dependent is the result on how the operator sprays the device? Could they deliberately just spray the area of the device of interest and how would this relate to the SpecimenArea (mm²) and SignalArea (mm²)?
A13) The ProReveal unit is normally intended to provide a simple pass/fail indication for the washing process rather than make precise measurements. The operator should be encouraged to spray the whole sample thoroughly to minimise variations in the spray pattern from measurement to measurement.
Q14) Would it be correct to say that a device could pass from one side and fail from the other?
A14) Any surgical instrument (or any other object) might have more contamination on one side compared to the other, depending on how it has previously been used and handled. All measurements are made from a single two-dimensional view of the top surface of the surgical instrument, so no account can be made of any parts of the object such as base or sides which are not directly visible to the camera.
Q15) How representative is the ProReveal Tag compared to the washing of a surgical instrument?
A15) The protein bound to the tag is much stronger than the normal soil contamination on a surgical instrument. It is optimised such that when a good wash condition is established all of it can be removed and verified. The ProReveal Tag has been compared to “Edinburgh soil” and “Pereg Tosi strips” and 11 other indicators available on the market. The combination of hydrophobic proteins, salts, lipids and carbohydrates make it a true representation of a stick tissue such as a brain. Quite simply if you can clean a ProReveal Tag, you can clean a dirty surgical instrument.
Q16) How often should a ProReveal Tag be used?
A16) It is suggested that an instrument check is done at least once a week along with a ProReveal Tag test. The tags are a process validation that gives added weight to audits, confidence and troubleshooting. Tags can be used to identify weak spots and bad loading.