CMDRT - Certified Medical Device Reprocessing Technician High-Level Disinfection Questions and Answers 2 — Questions and Answers

Question 1: Which of the following is an example of a high-level disinfectant approved for use in Canadian healthcare facilities?

Isopropyl alcohol 70%
Ortho-phthalaldehyde (OPA) (Correct answer)
Quaternary ammonium compounds
Household bleach at standard dilution

Correct answer: Ortho-phthalaldehyde (OPA)

OPA is a widely used high-level disinfectant in Canadian healthcare. It is effective against a broad spectrum of microorganisms, has a shorter contact time than glutaraldehyde, and is less irritating to mucous membranes.

Ortho-phthalaldehyde (OPA, commonly sold as Cidex OPA) is one of several Health Canada-approved high-level disinfectants used in medical device reprocessing. OPA offers several advantages over glutaraldehyde: it has a shorter contact time for HLD (typically 12 minutes at 20°C versus 45 minutes for many glutaraldehyde formulations), produces less irritating vapour, does not require activation, and has a longer reuse life. However, OPA can stain proteins grey, making it important that instruments are thoroughly cleaned before immersion. Other approved HLD agents include glutaraldehyde (2.4% or higher), hydrogen peroxide (7.5%), and peracetic acid. Quaternary ammonium compounds and standard bleach dilutions are low-level disinfectants only. The choice of HLD agent must be compatible with both the device and the AER if one is used.

Question 2: What is the critical difference between high-level disinfection and sterilization?

There is no meaningful difference
High-level disinfection eliminates most microorganisms but may not kill all bacterial spores, while sterilization destroys all forms of microbial life including spores (Correct answer)
Sterilization is faster than high-level disinfection
High-level disinfection is only used for non-critical devices

Correct answer: High-level disinfection eliminates most microorganisms but may not kill all bacterial spores, while sterilization destroys all forms of microbial life including spores

Sterilization achieves complete destruction of all microorganisms including highly resistant bacterial endospores. High-level disinfection eliminates vegetative bacteria, viruses, fungi, and mycobacteria but may not eliminate all spores, making it suitable for semi-critical but not critical devices.

The distinction between high-level disinfection and sterilization is fundamental to medical device reprocessing and is defined in CSA Z314.8. Sterilization is the complete destruction or elimination of all forms of microbial life, including the most resistant — bacterial endospores (e.g., Bacillus and Clostridium species). It is achieved through validated physical or chemical processes (steam, ETO, hydrogen peroxide plasma, etc.) and is required for critical medical devices that enter sterile body areas. High-level disinfection eliminates vegetative bacteria, mycobacteria (including M. tuberculosis), all fungi, and all viruses (both lipid and non-lipid enveloped), but may not destroy high numbers of bacterial spores. HLD is the minimum reprocessing requirement for semi-critical devices per the Spaulding classification.

Question 3: What must be done if the MEC test of a high-level disinfectant solution fails?

Add more water to dilute the solution
Continue using it for one more cycle only
Discard the solution immediately and replace with fresh disinfectant (Correct answer)
Heat the solution to restore its potency

Correct answer: Discard the solution immediately and replace with fresh disinfectant

A failed MEC test indicates the disinfectant can no longer achieve high-level disinfection. The solution must be discarded and replaced immediately — continuing to use it would put patients at risk of infection.

When a Minimum Effective Concentration (MEC) test fails, it means the active ingredient concentration has dropped below the threshold required to achieve high-level disinfection within the labelled contact time. This can occur through dilution from rinse water carry-over, chemical consumption by organic matter, evaporation, or simply reaching the end of the solution's reuse life. CSA Z314.8 is clear: the solution must be discarded and replaced with fresh disinfectant. There is no method to restore a depleted solution to its effective concentration — adding concentrate to used solution is not validated and is not acceptable. Any devices processed since the last successful MEC test must be recalled and reprocessed. The failed test must be documented, and the incident investigated per the facility's quality management program.

Question 4: Why is thorough cleaning essential before high-level disinfection?

Cleaning removes the need for disinfection
Organic soil remaining on devices can shield microorganisms from the disinfectant and inactivate the chemical agent (Correct answer)
Cleaning is optional if using a strong disinfectant
Cleaning only affects the appearance of instruments

Correct answer: Organic soil remaining on devices can shield microorganisms from the disinfectant and inactivate the chemical agent

Residual organic matter creates a physical barrier that prevents the disinfectant from contacting and killing microorganisms. Additionally, organic soil can chemically react with and deactivate some disinfectants, reducing their effectiveness.

The relationship between cleaning and high-level disinfection is one of the most important principles in medical device reprocessing. Cleaning must always precede disinfection for two critical reasons. First, organic matter (blood, tissue, biofilm) creates a physical barrier that prevents the disinfectant from making direct contact with microorganisms embedded in or beneath the soil. Second, many disinfectants — particularly glutaraldehyde and OPA — are partially inactivated by organic matter through chemical binding, which reduces the effective concentration of the solution. Studies have consistently shown that HLD is unreliable when performed on inadequately cleaned devices. CSA Z314.8 states that 'cleaning is the most important step in reprocessing' and that no amount of disinfection or sterilization can compensate for inadequate cleaning.

Question 5: What temperature and contact time parameters are critical for effective high-level disinfection?

Any temperature for any duration
The specific temperature and minimum contact time specified in the disinfectant manufacturer's instructions for use (Correct answer)
Room temperature for 5 minutes regardless of the product
Boiling temperature for 30 seconds

Correct answer: The specific temperature and minimum contact time specified in the disinfectant manufacturer's instructions for use

Each high-level disinfectant has validated parameters — specific minimum temperature and contact time — that must be met to achieve the claimed level of microbial kill. These parameters are determined by the manufacturer through standardized testing.

High-level disinfection effectiveness depends on four interrelated factors: the type and concentration of the disinfectant, temperature, contact time, and the nature of the microbial challenge (which is addressed by proper cleaning). Each HLD product has specific validated parameters that must be followed exactly. For example, 2.4% glutaraldehyde typically requires 45 minutes at 25°C for HLD, while OPA requires 12 minutes at 20°C. Peracetic acid may require only 5 minutes at specific concentrations. These parameters have been established through rigorous testing against standardized microbial challenges including mycobacteria (the benchmark organism for HLD). If the temperature falls below the minimum or the contact time is shortened, the disinfectant may not achieve HLD, even if the MEC is adequate. CSA Z314.8 requires facilities to follow the manufacturer's IFU and to monitor and document these parameters.

Question 6: How often should staff who perform high-level disinfection receive competency assessments?

Only during initial orientation
At least annually, and whenever new equipment or procedures are introduced (Correct answer)
Every five years
Competency assessments are not required for HLD

Correct answer: At least annually, and whenever new equipment or procedures are introduced

Annual competency assessments ensure that staff maintain their skills and knowledge of current procedures. Additional assessments are needed when new devices, chemicals, or equipment are introduced to the department.

Competency assessment for medical device reprocessing staff is a requirement under CSA Z314.8 and is mandated by most Canadian provincial regulatory frameworks. Staff must undergo initial training and competency verification before performing reprocessing tasks independently, followed by periodic reassessment — at minimum annually. Additional competency assessments are required when new devices, chemicals, equipment (such as a new AER model), or reprocessing procedures are introduced. Assessments should include both theoretical knowledge (understanding of HLD principles, chemical safety, IFU interpretation) and practical demonstration of skills (manual cleaning technique, MEC testing, AER operation, proper PPE use). Documentation of all training and competency assessments must be maintained. This is critical because studies have linked reprocessing breaches and infection outbreaks to inadequate staff training and competency.

CMDRT - Certified Medical Device Reprocessing Technician High-Level Disinfection Questions and Answers 2

Which of the following is an example of a high-level disinfectant approved for use in Canadian healthcare facilities?