Advanced Instrument Processing Solutions

In September 2011 I received this question from a SPD Tech. in reference to an approved value for the amount of residual soil on surgical instruments by the FDA. My answer was that the US FDA had no approved value number. Although this may be true for hospitals and ASC’s, I was recently informed that there is an FDA approved value for residual proteinaceous soil on surgical instrumentation . This FDA standard is for third party Single Use Device reprocessors and it set at less than six point four micrograms of protein per square centimeter (<6.4µg protein/cm²).

Although I had heard this value before in reference to the cleaning of flexible endoscopes (Alfa et al. 2002) as the average soil marker for biopsy/suction channel of clean flexible endoscopes, I did not know that this value had been set as the FDA standard for SUD reprocessors.

This value is also the basis of cleaning verification tests for flexible endoscopes (eg. Healthmarks ChannelCheck™ ). Who knows, maybe one day this verification value will apply to all surgical instruments processed in Healthcare facilities and not just the SUD Reprocessors it applies to now?…only time can tell.

Adenosine triphosphate, or ATP, testing only detects the presence of cells on surfaces; it will not detect the presence of protein or carbohydrates. Adenosine triphosphate is a co-enzyme that transports chemical energy within cells for metabolisim.

An ATP test consists of the following steps:

1. An object/surface is swabbed
2. The swab is then brought into contact with an enzyme called luciferase (the firefly enzyme)
3. The swab is then placed in a luminometer
4. Any ATP present on the swab will react with the luciferase and produce light which is read by the luminometer: the more light  produced, the more living organisms are present

This is a great test if you are trying to see how many living organisms are left on a surface following disinfection. What an ATP test won’t tell you is what they are. Furthermore, ATP will not detect the presence of viruses (viruses do not produce ATP).

To check for residual soil on instruments, you are better off with a test specifically targeted for residual protein and hemoglobin. These are also swab tests, and although they do not give quantitative amounts, they are quite sensitive (i.e. ProCheckII™ from Healthmark Industries is sensitive to 1µg of protein). Additionally, these tests do not require the purchase of extra equipment (e.g. luminometer) to interpret the results.

Lastly, the simplest test for blood residue on instruments is still the 3% hydrogen peroxide test.
To perform this test:

1. Place the instrument in question in a basin
2. Pour 3% hydrogen peroxide over it
3. If the solution begins to bubble around the instrument, this indicates there is residual blood soil

At present, there are no quantitative limits of residual protein on surgical instrumentation after decontamination in the United States. Both AAMI ST79 and ISO15883-1 identify “clean” as “the removal of contamination from an item to the extent necessary for its further processing and its intended subsequent use;” however, to this date in the United States, this has been interpreted as “visually clean.”

Recent publications* have demonstrated that even “visually clean” instruments are still capable of harboring unseen protein, lipid and carbohydrate soils. The average residual protein contamination of visually clean instruments in the Baxter study was 380µg. Because of studies like these, and the risks of vCJD transmission, two European nations (Germany and Austria) have begun to set limits of proteinaceous soil on instrumentation.

Germany (DGSV, DGKH, AKI)                             Austria (ÖGSV)
100µg per Instrument                                           50µg per Instrument
20µg per Opthalmic Instrument

As for the testing frequency of instruments or the method presently used to measure residuals in these countries, there is no definitive answer.

I myself recently posed this question of residual protein limits on surgical instruments at an FDA meeting on instrument reprocessing, and I also received no definitive answer.

 
*Publications:

1. Baxter RL, Baxter HC, Campbell GA, Grant K, Jones A, Richardson P, et al. Quantitative analysis of residual protein contamination on reprocessed surgical instruments. J Hosp Infect 2006;63(4):439-44.
2. Alfa MJ et al., Cleaning efficacy of medical device washers in North American healthcare facilities, J Hosp Infect 2009, doi:10.1016/j.jhin.2009.06.030)