NBSTSA Sterilization Methods & Instrument Processing — Questions and Answers
Question 1: Which sterilization method is considered the gold standard for heat- and moisture-tolerant surgical instruments?
- Ethylene oxide (EO) gas sterilization
- Steam (autoclave) sterilization (Correct answer)
- Hydrogen peroxide gas plasma sterilization
- Peracetic acid immersion sterilization
Correct answer: Steam (autoclave) sterilization
Steam sterilization (autoclaving) using saturated steam under pressure is the gold standard for heat- and moisture-stable instruments. It is the most widely used, cost-effective, well-validated, and fastest method available for standard instrument sets.
Question 2: Ethylene oxide (EO) gas sterilization is preferred for which category of items?
- Stainless steel surgical instruments
- Heat- and moisture-sensitive items such as flexible endoscopes and plastics (Correct answer)
- Instruments that must be available for immediate use
- Items potentially contaminated with prion disease
Correct answer: Heat- and moisture-sensitive items such as flexible endoscopes and plastics
EO is a low-temperature sterilization method suitable for items that cannot tolerate the heat and moisture of steam sterilization, such as flexible endoscopes, cameras, plastic components, and rubber items. A major drawback is the prolonged aeration time required (hours to days) before items are safe to use.
Question 3: A Class 5 chemical integrator placed inside a sterilization package changes to the correct endpoint color. What does this confirm?
- The outside of the package was exposed to steam
- All critical sterilization parameters (time, temperature, and steam) were met (Correct answer)
- The item inside is guaranteed to be sterile
- The package was exposed to the correct temperature only
Correct answer: All critical sterilization parameters (time, temperature, and steam) were met
Class 5 integrating indicators react to all critical parameters of a steam sterilization cycle: time, temperature, and the presence of saturated steam. Reaching the endpoint color confirms all three were achieved. However, they do not guarantee sterility — only a biological indicator (spore test) can verify that.
Question 4: A biological indicator (BI) from a sterilization load returns a positive (failed) result. What is the required immediate action?
- Re-sterilize the load and release the items
- Quarantine all items from that load and investigate the sterilizer failure (Correct answer)
- Run an additional chemical indicator test before releasing items
- Notify the surgeon and proceed if instruments appear visually clean
Correct answer: Quarantine all items from that load and investigate the sterilizer failure
A positive BI means living bacterial spores survived the cycle, indicating sterilization failure. All items from that load — and potentially previous loads back to the last negative BI — must be quarantined and recalled. The sterilizer must be taken out of service and investigated.
Question 5: Immediate Use Steam Sterilization (IUSS), formerly called flash sterilization, should be used in which circumstance?
- As a routine method for all instrument sets to save time
- Only when an item is urgently needed and no sterile replacement is available (Correct answer)
- For all implantable devices to ensure the highest sterility level
- Whenever standard sterilization packaging materials are unavailable
Correct answer: Only when an item is urgently needed and no sterile replacement is available
IUSS is intended only for emergency situations where a needed item is contaminated or dropped intraoperatively and no pre-packaged sterile replacement is available. It should never be used routinely because items are transported without packaging, increasing contamination risk, and cycle monitoring is reduced.
Question 6: Which low-temperature sterilization method uses vaporized hydrogen peroxide combined with plasma energy and produces only water vapor and oxygen as byproducts?
- Ethylene oxide (ETO) sterilization
- Dry heat sterilization
- Hydrogen peroxide gas plasma (Sterrad) (Correct answer)
- Peracetic acid immersion (Steris)
Correct answer: Hydrogen peroxide gas plasma (Sterrad)
Hydrogen peroxide gas plasma sterilization (brand name Sterrad) uses vaporized hydrogen peroxide energized into a plasma state at low temperatures. It is effective for moisture-sensitive instruments, requires no aeration period, and produces only non-toxic byproducts (water vapor and oxygen).
