- Diagnostic Parasitology
In the wake of a report of endoscopy-related transmission of hepatitis C virus1, we have received requests for information about the efficacy of glutaradehyde based disinfectants, such as Wavicide-01, against HCV. The incident in question was caused by poor processing of the scope and not by disinfectant failure2. The endoscope had not been properly cleaned and had been immersed in disinfectant for only five minutes. According to APIC, glutaraldehyde is still recommended as one of the preferred agents for high level disinfection of endoscopes3.
- Bronowicki JP, et al. Patient-to-patient transmission of hepatitis C virus during colonscopy. N Eng J Med 1997; 337:237-240.
- Alvarado CJ. Reichelderfer M. APIC guideline for infection prevention and control in flexible endoscopy. Am J Infect Control 2000; 28:138-55 (http://www.apic.org/pdf/gdendosc.pdf).
- Ibid, pg. 147.
A common question that is routinely asked is what is the difference between a 14 days and a 28 days glutaraldehyde solution? Which should I use? Why is Wavicide-01 a 30 days solution? Please explain?
Originally, when the first glutaraldehyde product appeared on the market, it was a 14 day alkaline solution. It was discovered that when the pH of a glutaraldehyde solution is raised to very high levels, above 9, the cidal activity is increased.. but the glutaraldehyde begins to polymerize at a much faster rate. Two weeks after activation, whether is has been used or not, the MEC (Minimum Effective Concentration) of the glutaraldehyde is now below the threshold where the product is effective as a disinfectant and the solution should be discarded. With the addition of some surfactants and a lower pH the glutaraldehyde product becomes a 28 days solution, after activation whether it has been used or not. 100% Tuberculocidal inactivation goes from 45 minutes for the 14 days solution to 90 minutes for the 28 days solution.
Wavicide-01 works at an even lower pH and is pre-activated, the unused product remaining in the bottle is good for one year from the manufacturing date. Like a 14 days solution, TB is inactivated in 45 minutes, yet the product is good for thirty days from the date of first use. It is very important that the concentration of all glutaraldehyde disinfectants be monitored daily or even more often depending on your application using monitor strips to make sure it remains above MEC (a glutaraldehyde product below its Minimum Effective Concentration is ineffective). For applications like endoscope disinfection where typically a pre-washed wet device is submerged in the solution, the product is continually being diluted and the glutaraldehyde concentration will drop at a very high rate, much shorter than the 14, 28 or 30 days mentioned on the label.
We would like to steer users away from the notion of “days of use” to the importance of monitoring glutaraldehyde concentration which is the important factor in determining whether or not the product is effective. The “day of use” period reflect the maximum period of time the product can be in use regardless of the fact its concentration is still above MEC.
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