22 Asepsis & Sterile Technique Practice Questions & Answers

1. 1. Which area of a properly donned sterile gown is considered sterile?

   • A.The front from the neckline to the hem, including the axillary region covered by the drape
   • B.The sleeves and the knit stockinette cuffs, which stay sterile after the gloves are pulled on
   • C.The entire garment from the neckline to the hem once the back closure has been fastened
   • D.The front from chest level to the field and the sleeves from cuff to two inches above the elbow✓ Answer

   A sterile gown is sterile in front from mid-chest to the level of the sterile field and on the sleeves from the cuff to about two inches above the elbow. The back, neckline, shoulders, axilla and the knit cuffs are not sterile because they cannot be kept under direct observation and the cuffs absorb moisture, which is why a gowned person never turns the back to the field.

   Source: AST Standards of Practice for Gowning and Gloving — sterile boundaries of the surgical gownReport a problem with this question

2. 2. During setup a sterile towel slips over the edge of the back table and hangs down the side. What should the CST do?

   • A.Consider the towel contaminated, leave it hanging, and open a replacement towel✓ Answer
   • B.Treat only the portion hanging below the table edge as contaminated and reuse it
   • C.Lift the towel back onto the table and cover the area with a second sterile drape
   • D.Retrieve it with a sterile gloved hand, since the towel never contacted the floor

   Draped tables are sterile at table-top level only. Anything that falls below the edge of the table is out of sight and outside the sterile boundary, so it is considered contaminated and is never lifted back onto the field; the CST leaves it undisturbed and opens a replacement.

   Source: AST Guidelines for Best Practices in Establishing the Sterile Field — table-top level sterile boundaryReport a problem with this question

3. 3. Two scrubbed team members must exchange positions at the sterile field. How should they move?

   • A.They pass back to back or front to front, keeping their sterile fronts accounted for✓ Answer
   • B.They pass front to back, each keeping one hand flat on the sterile drape while moving
   • C.One turns to face the wall while the other steps behind and takes the vacated place
   • D.Both step back from the field and walk around the foot of the operating table drape

   Only the front of a sterile gown from mid-chest to field level is sterile and the back is not, so scrubbed persons pass one another back to back or front to front. Passing front to back would turn a sterile front against an unsterile back and contaminate it.

   Source: AST Standards of Practice for Gowning and Gloving — movement of sterile persons at the fieldReport a problem with this question

4. 4. Irrigation fluid has soaked completely through a drape to the non-sterile surface beneath it. How is that area regarded?

   • A.Sterile, provided the drape is blotted dry with a sterile towel before use continues
   • B.Contaminated by strike-through; the wet area is covered with sterile drape or replaced✓ Answer
   • C.Sterile, because the fluid spilled on the field came from a sterile irrigation container
   • D.Contaminated only if the fluid also reaches the floor beneath the operating table

   Strike-through is the passage of fluid through a barrier, and the moisture creates a continuous path that lets microorganisms migrate from the non-sterile surface up into the field. Once a drape is soaked through, that area is contaminated regardless of the sterility of the fluid itself and must be covered with additional sterile drape or replaced.

   Source: AST Standards of Practice for Gowning and Gloving — strike-through contamination and barrier integrityReport a problem with this question

5. 5. The CST is the only person who sees a circulator's sleeve brush the edge of the sterile back table. What is the correct action?

   • A.Say nothing, because contact by a clean scrub-suit sleeve is not a true break in technique
   • B.Move the instruments away from that corner of the table and quietly continue the setup
   • C.State the contamination out loud at once so the affected area can be covered or replaced✓ Answer
   • D.Wait until the procedure is over and report the event privately to the charge nurse

   Any team member who observes a break in technique is obliged to identify it immediately and out loud, whatever the role or seniority of the person who caused it. Delay allows contaminated items to be used, so the break is named at once and the affected area is covered, replaced, or the person regowned.

   Source: NBSTSA CST Examination Content Outline, Intraoperative Procedures item 1 — handling breaks in sterile techniqueReport a problem with this question

6. 6. A scrubbed CST's glove is punctured during a procedure while the gown sleeve stays intact. What is the correct remedy?

   • A.Cover the puncture with a sterile adhesive strip and finish the current step first
   • B.Step back from the field, have the glove removed, and be regloved by a sterile member✓ Answer
   • C.Change the gown and both gloves, since a glove breach always contaminates the gown
   • D.Pull a second sterile glove over the punctured one and return to the field at once

   A glove breach with an intact gown is corrected by a glove change: the scrubbed person steps back from the field, the contaminated glove is removed, and a sterile team member regloves them. Pulling a fresh glove over a punctured one traps contamination against the hand, and the gown is changed only when the gown itself is contaminated.

   Source: AST Standards of Practice for Gowning and Gloving — remedy for a contaminated glove with an intact gownReport a problem with this question

7. 7. After the surgical scrub, which gloving method is preferred for the initial gown and gloves?

   • A.Open gloving followed by a second closed glove pulled over the first for security
   • B.Closed gloving, with the hands kept inside the gown cuffs throughout the procedure✓ Answer
   • C.Assisted gloving by the circulator, who holds each glove open at the sterile cuff
   • D.Open gloving, with the cuffs folded back so the bare fingertips can seat the glove

   Closed gloving is the method of choice for the initial gown and gloves because the scrubbed hands remain inside the gown cuffs and never touch the outside of the glove or extend past the knit cuff, which is not sterile. Open gloving is reserved for tasks such as urinary catheterization or for regloving without changing the gown.

   Source: AST Standards of Practice for Gowning and Gloving — closed gloving as the method of choiceReport a problem with this question

8. 8. Where should the CST's own gown and gloves be opened before scrubbing?

   • A.On a separate small table or Mayo stand set apart from the sterile back table✓ Answer
   • B.On the corner of the sterile back table, directly on top of the back table drape
   • C.Inside the sterile ring basin so that water dripping from the arms is contained
   • D.On the draped operating table so the CST gowns close to the planned incision

   The CST's gown and gloves are opened on a separate flat surface away from the back table so that water dripping from the scrubbed arms cannot wet the back table drape and cause strike-through, and so that the CST never has to reach over a sterile field while gowning.

   Source: AST Guidelines for Best Practices in Establishing the Sterile Field — opening gown and gloves on a separate surfaceReport a problem with this question

9. 9. A tray in an impervious wrapper is dropped on a dry floor; on inspection the wrapper is intact and dry. What is correct?

   • A.It may go back on the sterile shelf if its external indicator still shows a color change
   • B.It may be used after the outer wrapper is wiped down with an approved disinfectant
   • C.It may be used at once for that case and must never be returned to the storage shelf✓ Answer
   • D.It must be reprocessed, because any package that contacts the floor becomes unsterile

   The decision turns on the wrapper, not on the floor. A package in impervious material that is inspected and found intact and dry may be used immediately for that case, because moisture and airborne contaminants did not penetrate the barrier; it may not go back into storage, since the drop and the handling are contaminating events. A pervious woven wrap dropped on the floor is unsterile and must be reprocessed.

   Source: AST Guidelines for Best Practices for Sterile Wrapped Items Dropped on the FloorReport a problem with this question

10. 10. A circulator pours sterile saline into a basin on the field and solution remains in the bottle. What must be done with the remainder?

    • A.It is capped and labeled with the opening time for use later in the same case
    • B.It is left uncapped on the back counter and poured again during the procedure
    • C.It is discarded, because a recapped bottle cannot be guaranteed to remain sterile✓ Answer
    • D.It is poured into a second sterile basin so that none of the solution is wasted

    Once a sterile solution is opened the entire contents are poured out or the remainder is discarded. The lip of the container and its cap are no longer sterile, and the sterility of a recapped bottle cannot be guaranteed, so leftover solution is never saved for later use.

    Source: AST Guidelines for Best Practices in Establishing the Sterile Field — pouring sterile solutionsReport a problem with this question

11. 11. Opening an instrument set, the CST sees that several ratcheted clamps are closed on the first ratchet. What is the correct conclusion?

    • A.The clamps may be used once they are opened and rinsed with sterile water
    • B.The tray is acceptable if its internal chemical indicator has changed correctly
    • C.Only the closed instruments are unsterile and they are handed off to the circulator
    • D.The whole tray is considered unsterile and is returned for cleaning and reprocessing✓ Answer

    Sterilant must contact every surface of an instrument, so ratcheted instruments are processed open and unlocked. A clamp closed on its ratchet shields the box lock and jaw surfaces, so sterilization cannot be assumed for that set and the entire tray is returned to be cleaned and reprocessed.

    Source: AST Guidelines for Best Practices in Establishing the Sterile Field — instruments processed open and unlockedReport a problem with this question

12. 12. A stored package is still within its printed date, but its wrapper has a small tear. What governs whether it may be used?

    • A.The external indicator; a changed indicator confirms the contents are still sterile
    • B.The load record; a negative biological indicator keeps it sterile until the date passes
    • C.Event-related sterility; the tear is a contaminating event, so the item is reprocessed✓ Answer
    • D.Time-related sterility; the printed date has not passed, so the package may be used

    Current practice uses event-related sterility: a package stays sterile until an event compromises it, not until a date passes. A tear, moisture, or excessive handling is a contaminating event, so the printed date is irrelevant here and the item is returned for reprocessing.

    Source: ANSI/AAMI ST79 event-related sterility, applied in AST Guidelines for Best Practices in Establishing the Sterile FieldReport a problem with this question

13. 13. The external chemical indicator tape on a wrapped tray has changed color. What has this demonstrated?

    • A.That the package was exposed to the process; only a biological indicator proves lethality✓ Answer
    • B.That every critical variable of the cycle reached the value set by the manufacturer
    • C.That the sterilant penetrated to the center of the package during the exposure phase
    • D.That the contents are sterile and the tray may be delivered to the sterile field

    An external Class 1 chemical indicator such as autoclave tape is a process indicator: it distinguishes a processed package from an unprocessed one and proves nothing about the conditions inside the package or about killing. Only a biological indicator, which contains resistant spores, directly demonstrates that the process was lethal.

    Source: AST Guidelines for Best Practices in Monitoring Sterility — chemical indicator classes; CDC Guideline for Disinfection and SterilizationReport a problem with this question

14. 14. Which spore-forming organism is used in the biological indicator for a steam sterilization load?

    • A.Bacillus atrophaeus, selected for its high resistance to saturated steam exposure
    • B.Staphylococcus aureus, selected for its frequency as a surgical site pathogen
    • C.Geobacillus stearothermophilus, selected for its high resistance to moist heat✓ Answer
    • D.Clostridium sporogenes, selected for its anaerobic growth inside wrapped trays

    Steam sterilization is monitored with Geobacillus stearothermophilus because its spores are highly resistant to moist heat; if they are killed, less resistant organisms have been killed as well. Bacillus atrophaeus is the spore used for ethylene oxide, and candidates commonly reverse the two.

    Source: CDC Guideline for Disinfection and Sterilization in Healthcare Facilities — biological indicators for steam and ethylene oxideReport a problem with this question

15. 15. Which monitoring requirement applies to a sterilizer load that contains an implant?

    • A.A Bowie-Dick test run ahead of the load, which confirms air removal for implant trays
    • B.A Class 5 integrating indicator in the tray, which allows the implant to be released now
    • C.An external process indicator on the container, checked by the CST during the setup
    • D.A process challenge device with a biological indicator, the implant held until it is read✓ Answer

    Every load containing an implant is monitored with a process challenge device holding a biological indicator together with a Class 5 integrating indicator, and the implant is quarantined until the biological result is read. A Class 5 indicator contains no spores, so it can never substitute for the biological indicator; early release is a documented emergency exception.

    Source: AST Guidelines for Best Practices in Monitoring Sterility — implant loads and quarantineReport a problem with this question

16. 16. A biological indicator from a steam sterilizer is reported positive. What is the correct response?

    • A.Repeat the test and keep using the sterilizer while the repeat result is still pending
    • B.Recall only the single load that contained the positive biological indicator and rerun it
    • C.Recall every item processed in that sterilizer since the last negative biological indicator✓ Answer
    • D.Recall the load, then release the items whose Class 5 integrating indicators passed

    A positive biological indicator means spores survived, so the sterilizer's performance is in doubt back to the last time it was proven lethal. Every item processed in that sterilizer since the last negative biological indicator is recalled, the sterilizer is taken out of service, and the cause is investigated.

    Source: AST Guidelines for Best Practices in Monitoring Sterility — response to a positive biological indicatorReport a problem with this question

17. 17. A lumened instrument arrives in decontamination with dried blood in its channel. What must happen FIRST?

    • A.A rinse of the lumen with sterile water and packaging for a longer sterilizer cycle
    • B.Immersion in a high-level disinfectant to lower the bioburden inside the lumen
    • C.Thorough cleaning that removes all organic soil from the lumen and outer surfaces✓ Answer
    • D.A lengthened sterilizer exposure time that compensates for the residual soil

    Cleaning always precedes disinfection and sterilization. Organic soil such as dried blood shields microorganisms from the sterilant and can prevent contact altogether, so no cycle and no disinfectant immersion can be relied on until the lumen and all surfaces have been thoroughly cleaned; point-of-use pre-treatment keeps soil from drying in the first place.

    Source: CDC Guideline for Disinfection and Sterilization — cleaning precedes disinfection and sterilization; NBSTSA CST Exam Content Outline, Equipment Sterilization and MaintenanceReport a problem with this question

18. 18. Under the Spaulding classification, how is a laryngoscope blade that contacts mucous membranes categorized?

    • A.Critical, calling for terminal sterilization before every single patient use
    • B.Noncritical, calling for detergent cleaning and thorough drying between uses
    • C.Noncritical, calling for intermediate-level disinfection of the outer surfaces
    • D.Semicritical, calling for sterilization or at minimum high-level disinfection✓ Answer

    Spaulding classifies devices by the risk of the tissue they contact. Items that touch mucous membranes or non-intact skin, such as laryngoscope blades and flexible endoscopes, are semicritical and require sterilization or at least high-level disinfection; critical items enter sterile tissue or the vascular system and must be sterilized.

    Source: CDC Guideline for Disinfection and Sterilization — Spaulding classificationReport a problem with this question

19. 19. A flexible, heat- and moisture-sensitive lumened device requires sterilization. Which method is indicated?

    • A.Dry heat sterilization, because no moisture ever reaches the interior of the lumen
    • B.Immersion in 70 percent alcohol, which is broad spectrum and non-corrosive to it
    • C.A low-temperature method such as hydrogen peroxide gas plasma or ethylene oxide✓ Answer
    • D.A prevacuum steam cycle, because dynamic air removal protects the delicate lumen

    Steam is the method of choice only when the device tolerates heat and moisture. A flexible heat- and moisture-sensitive lumened device is processed by a low-temperature method such as hydrogen peroxide gas plasma, ethylene oxide, or peracetic acid immersion. Alcohol is not sporicidal and therefore never sterilizes.

    Source: CDC Guideline for Disinfection and Sterilization — low-temperature sterilization of heat- and moisture-sensitive devicesReport a problem with this question

20. 20. Which statement about immediate-use steam sterilization (IUSS) is correct?

    • A.It is limited to a genuine immediate need and does not replace terminal sterilization✓ Answer
    • B.It removes the need for the biological monitoring required of wrapped steam loads
    • C.It is the preferred process for implants because the item is unwrapped and handled fast
    • D.It is an accepted routine method whenever instrument inventory is short for a case

    Immediate-use steam sterilization is intended for an item that is needed right away and cannot be processed by the usual route. It is not a substitute for terminal sterilization, it is not to be used for convenience or to make up for inadequate instrument inventory, and it is not the routine method for implants.

    Source: CDC Guideline for Disinfection and Sterilization — immediate-use steam sterilization (IUSS)Report a problem with this question

21. 21. The umbilicus lies inside the prep field for an abdominal procedure. When is it prepped?

    • A.Last, after the surrounding skin, because it is treated as a contaminated area
    • B.First, with soaked applicators, before the surrounding abdominal skin is prepped✓ Answer
    • C.At the same time as the surrounding skin, using the same expanding circular strokes
    • D.Never, since it is covered with a sterile adhesive drape before the prep begins

    Contaminated areas are normally prepped last, but the umbilicus is the recognized exception. When it lies within the prep field it is cleaned first, usually with solution-soaked cotton-tipped applicators, so that its debris and soiled solution do not run or splash onto abdominal skin that has already been prepped.

    Source: AST Standards of Practice for Skin Prep of the Surgical Patient — the umbilicus is prepped firstReport a problem with this question

22. 22. A major break in sterile technique occurs during an otherwise clean abdominal procedure. How is the wound classified?

    • A.Class II, clean-contaminated, the class used for controlled entry of a tract
    • B.Class IV, dirty-infected, because organisms entered an already infected field
    • C.Class I, clean, because the wound stayed closed and free of any inflammation
    • D.Class III, contaminated, which is the class assigned when a major break occurs✓ Answer

    A major break in sterile technique reclassifies the wound as Class III, contaminated, along with open fresh accidental wounds, gross gastrointestinal spillage, and acute non-purulent inflammation. Class I remains clean only when no such break occurs and no tract is entered.

    Source: CDC surgical wound classification, Class I–IV; NBSTSA CST Exam Content Outline, Microbiology — surgical wound classificationReport a problem with this question

Practice questions based on the NBSTSA Certified Surgical Technologist exam content outline, AST standards of practice, and durable operating-room principles. CST is a mark of the National Board of Surgical Technology and Surgical Assisting; this site is not affiliated with or endorsed by NBSTSA or AST. Surgical counts, documentation, and what a technologist may perform are governed by your facility's policy and by state law, and sterilization parameters follow the manufacturer's written instructions — confirm all of these locally rather than from a practice test, and confirm current eligibility and exam requirements with the certifying board. About the CST exam →