21 Asepsis & Sterile Technique Practice Questions & Answers

1. 1. Which outcome does a sterilization process guarantee that a high-level disinfection process does NOT?

   • A.Killing of vegetative bacteria and lipid-enveloped viruses only
   • B.Reduction of the number of microorganisms to a safe level
   • C.Destruction of all microbial life, including bacterial spores✓ Answer
   • D.Removal of all visible soil and organic debris from the item

   Sterilization is defined by the destruction of ALL microbial life, and bacterial spores are the benchmark because they are the most resistant common form of microbial life (only prions are harder to kill). High-level disinfection kills vegetative bacteria, most viruses and fungi and the tubercle bacillus, but cannot be relied on to kill large numbers of spores; cleaning only removes soil and sanitization only reduces counts. This is why Spaulding classifies any item entering sterile tissue or the vascular system as critical and requires sterilization for it.

   Source: Spaulding classification of instrument processing — sterilization versus high-level disinfectionReport a problem with this question

2. 2. In which area of the surgical suite is a mask required IN ADDITION to a scrub suit and head covering?

   • A.The unrestricted area, including the preoperative holding area and offices
   • B.The semi-restricted area, including peripheral corridors and sterile storage
   • C.Every area of the surgical suite, including locker rooms and lounges
   • D.The restricted area, including the operating rooms, sub-sterile rooms and scrub sink areas✓ Answer

   The surgical suite is divided into unrestricted (street clothes permitted), semi-restricted (surgical attire and head covering) and restricted areas, and the mask is added in the restricted area because that is where sterile supplies are opened and sterile fields are established, so droplets from the nose and mouth could reach them directly. The scrub sink and sub-sterile rooms are part of the restricted zone for that reason, even though no incision is made there. Attire escalates zone by zone because the purpose is to protect open sterile items from the personnel, not simply to mark territory.

   Source: AORN and AST guidance on surgical attire and the traffic zones of the surgical suiteReport a problem with this question

3. 3. Which requirement applies to EVERY member of the surgical team, in every role?

   • A.The warm-up jacket may be tied at the waist during the surgical scrub
   • B.Shoe covers must be worn because they lower the surgical site infection rate
   • C.Artificial nails and nail overlays may not be worn✓ Answer
   • D.Nail polish is prohibited under all circumstances

   Artificial nails and overlays are prohibited for all perioperative personnel in all roles because higher numbers of pathogens, including gram-negative bacilli and yeasts, are recovered from the subungual area and from the seam between the natural and artificial nail, and neither hand hygiene nor a surgical scrub reliably removes them. Nail polish is treated differently — it is governed by facility policy and is acceptable only when freshly applied and unchipped, since chipped or aged polish harbors organisms. Shoe covers protect the wearer from blood and body fluids but have never been shown to reduce infection rates or floor bacterial counts, and the warm-up jacket must be completely removed before scrubbing rather than tied.

   Source: AST Standards of Practice for Surgical Attire, Surgical Scrub, Hand Hygiene and Hand WashingReport a problem with this question

4. 4. During closed gloving, the scrubbed CST keeps both hands inside the gown sleeves until the gloves are in place. The reason is that

   • A.the stockinette cuffs of the gown are not considered sterile✓ Answer
   • B.the cuffs are sterile but tear easily against the fingernails
   • C.the back of the gown can be contaminated by the circulator
   • D.the sleeves must stay dry to prevent strike-through contamination

   The stockinette cuff is not an effective microbial barrier — it absorbs perspiration and is considered nonsterile from the moment the hands pass beyond it — so closed gloving keeps the hands behind the cuff and uses them through the fabric to draw the sterile glove over the cuff without the skin ever touching the glove's outside. The sterile areas of a donned gown are the front from the chest down to the level of the sterile field and the sleeves from above the elbow to the cuff; the cuff itself is excluded. This is also why a glove change at the field is done by the closed or assisted method rather than by open gloving over an exposed cuff.

   Source: AST Guidelines for Best Practices — sterile areas of the surgical gown and closed glovingReport a problem with this question

5. 5. While retracting, the CST feels a glove tear. No one else has noticed. What should the CST do FIRST?

   • A.Wait for a pause in the procedure before mentioning it
   • B.Remove the glove and apply a new one by the open glove method
   • C.Announce the contamination immediately and step back from the sterile field✓ Answer
   • D.Pull a second glove over the torn glove and continue retracting

   Surgical conscience requires the individual who breaks technique to report it immediately, even when no one else saw it, because the contaminated glove is in direct contact with the wound and every additional second increases inoculation of the patient. The CST steps back, extends the arm so the circulator can deglove without touching the sterile gown, and is re-gloved by the closed or assisted method; open gloving is wrong here because the exposed stockinette cuff is nonsterile and would contaminate the new glove. Waiting for a convenient moment or double-gloving over the tear leaves contaminated material at the field.

   Source: AST Guidelines for Best Practices — surgical conscience and correction of breaks in sterile techniqueReport a problem with this question

6. 6. A scrubbed CST's gown sleeve becomes contaminated during a procedure. In what order are the gown and gloves removed so that re-gowning can take place?

   • A.Gown and gloves are pulled off together by the circulator
   • B.The gown is removed first, then the gloves✓ Answer
   • C.Neither is removed; the sleeve is covered with a sterile towel
   • D.The gloves are removed first, then the gown

   The gown is removed first, pulled forward and turned inside out so that the contaminated outer surface rolls away from the wearer, and the gloves are deliberately left on during this step so the hands are protected from that contaminated exterior. The gloves are removed only afterward, and the CST is then re-gowned and re-gloved by a scrubbed team member or by the closed method after regloving. Covering a contaminated sleeve is not acceptable because the sleeve moves continuously over the wound and the cover cannot be secured or monitored.

   Source: AST Guidelines for Best Practices — managing contamination of the gown during a procedureReport a problem with this question

7. 7. An alcohol-based skin prep has been applied. Before the drapes are placed, it is ESSENTIAL that

   • A.the prepped area is covered with a warm, moist towel
   • B.the solution has dried completely and any pooled solution has been blotted away✓ Answer
   • C.the prep solution is applied a second time over the incision line
   • D.the electrosurgical unit is set to its lowest available power setting

   Alcohol-based preps give off flammable vapor while they are wet, and draping over a wet prep traps that vapor in an oxygen-enriched space under the drapes where an electrosurgical active electrode or laser can ignite it — this is a leading cause of surgical fires. Solution that pools beneath the patient or wicks into linens and under electrodes also remains a fuel source and can cause a chemical burn, so it is blotted before draping. Drying time is determined by the product's own instructions, not by a fixed interval the team chooses.

   Source: AORN guidance on skin antisepsis with flammable prep agents and surgical fire preventionReport a problem with this question

8. 8. A midline abdominal incision is planned in a patient whose colostomy lies within the area to be prepped. How is the prep performed?

   • A.Prep the clean skin first in widening circles, then prep the stoma last with a separate sponge✓ Answer
   • B.Prep the whole area with one sponge, returning to the incision line between strokes
   • C.Prep the stoma first, then move outward from it over the clean skin
   • D.Cover the stoma with a towel and prep only the intended incision line

   The prep starts at the intended incision site and moves outward in widening concentric circles, and the sponge is discarded at the periphery and never returned to the center, because a sponge that has crossed less clean skin would carry those organisms back to the site of the incision. A colostomy, like the umbilicus, an open wound, the anus or the vagina, is a heavily colonized area and is prepped last with a separate sponge for the same reason. The prepped area is also made wider than the anticipated incision so the field can accommodate extension of the incision or placement of drains without re-prepping.

   Source: AORN guideline for preoperative patient skin antisepsis — prepping the contaminated area lastReport a problem with this question

9. 9. A drape is released slightly off target and sits a little too low over the operative site. What should be done?

   • A.Lift the drape clear of the patient and lay it down again on target
   • B.Have the circulator pull the drape into place from underneath
   • C.Slide the drape upward into the correct position
   • D.Leave the drape where it is and cover the exposed area with an additional sterile drape✓ Answer

   Once a drape has been placed it is never moved or repositioned, because sliding it toward the operative site drags the nonsterile skin surface it has touched across the prepped area, and lifting it exposes the underside and creates air currents that carry contaminants over the field. The accepted correction is to leave the misplaced drape in position and cover the gap with another sterile drape, or to have the drape removed carefully away from the field and discarded before re-draping. Drapes are handled by holding them high, above table and waist level, with the gloved hands cuffed under the drape edge to protect them.

   Source: AST Guidelines for Best Practices — draping; a drape is not moved once it has been placedReport a problem with this question

10. 10. A pair of scissors slips off the back table and is caught in the drape hanging over the side, well below the tabletop. The CST should

    • A.leave the scissors in the fold of the drape and report the count as correct
    • B.wipe the scissors with a moist sterile sponge and return them to the Mayo stand
    • C.lift the scissors straight back onto the table, since they never reached the floor
    • D.consider the scissors contaminated and have the circulator remove them from the field✓ Answer

    Only the top of a draped table is sterile; the portion of the drape hanging below the tabletop cannot be seen or monitored and is nonsterile, so anything that falls below the table edge is contaminated and is never retrieved and brought back up. Wiping does not restore sterility, and an item of doubtful sterility is by rule treated as contaminated. The circulator removes the scissors from the field, but they stay in the room and are included in the count until the procedure ends.

    Source: AST Guidelines for Best Practices for Establishing the Sterile Field — only the top of a draped table is sterileReport a problem with this question

11. 11. Which part of a properly donned sterile gown is considered NONSTERILE?

    • A.The sleeve from above the elbow down to the cuff
    • B.The front of the gown from the chest to the level of the sterile field
    • C.The front of the forearm while the hands are held in view
    • D.The area under the arms and across the back of the gown✓ Answer

    The back of the gown and the underarm area are nonsterile because they cannot be kept under continuous observation, and the governing principle is that a sterile area must be watched to be trusted; the neckline, shoulders and the stockinette cuffs are excluded for the same reason. The sterile areas are the front from chest level down to the level of the sterile field and the sleeves from above the elbow to the cuff. This is the rationale behind keeping the hands above waist level and in sight, never turning the back to the field, and passing another sterile person back to back.

    Source: AST Guidelines for Best Practices — sterile areas of the surgical gownReport a problem with this question

12. 12. Two scrubbed team members must change places at the operating table. They should

    • A.step away from the field, lower their hands, and walk around the back table
    • B.turn back to back and pass, each keeping the gown front toward the sterile field✓ Answer
    • C.pass front to front so that each can watch the other's gloved hands
    • D.ask the circulator to hold the drapes aside while they pass front to back

    Sterile team members pass back to back because the back of the gown is nonsterile and unobservable, so turning back to back keeps each person's sterile front facing the sterile field and prevents a nonsterile back from brushing a sterile front. The complementary rules are that a sterile person faces the sterile field at all times and never turns away from it or leans over a nonsterile area, while an unsterile person faces the field, keeps a safe distance, never reaches over it, and never walks between two sterile fields. Lowering the hands below waist level would itself contaminate them.

    Source: AORN Guideline for Sterile Technique — movement within and around the sterile fieldReport a problem with this question

13. 13. The room has been set up but the case is delayed. What is the correct handling of the sterile field?

    • A.It must be continuously monitored, or covered with a sterile drape that does not extend below the table edges✓ Answer
    • B.It should be covered with a drape long enough to hang over all four table edges
    • C.It may be left uncovered for a fixed maximum number of hours before it must be discarded
    • D.It may be left unattended as long as the operating room doors stay closed

    A sterile field that is not continuously observed is considered contaminated, because contamination is an event that can only be detected by someone watching for it. If the field cannot be watched, it is covered with a sterile drape that stays at or above the table edges — a cover that hangs below the edge is itself nonsterile below that line and could not be lifted off without drawing that portion up across the sterile tabletop — and the cover is removed by lifting it straight up and away from the table. Research has not established a maximum length of time a covered field may stand, so no fixed number of hours can be relied on.

    Source: AST Guidelines for Best Practices and AORN Guideline for Sterile Technique — monitoring and covering the sterile fieldReport a problem with this question

14. 14. Irrigation solution spills and soaks through the back table cover to the table surface beneath. The affected area is

    • A.contaminated only if the solution was poured from a nonsterile container
    • B.contaminated, because moisture provides a path for microorganisms to pass through the barrier✓ Answer
    • C.sterile, because the irrigation solution that was poured onto it was itself sterile
    • D.sterile, provided the area is blotted dry at once with a sterile towel

    This is strike-through: fluid wicking through a barrier creates a continuous moist path along which microorganisms migrate from the nonsterile surface below to the sterile surface above, so the sterility of the fluid itself is irrelevant. Blotting does not reverse it, because the organisms have already been drawn upward and the barrier has failed. The area is covered with a sterile drape or the affected portion of the setup is re-established, and prevention means using moisture-resistant barriers and not placing basins of solution where gowns, drapes or wrapped items can wick from them.

    Source: AST Guidelines for Best Practices — strike-through contamination of sterile barriersReport a problem with this question

15. 15. Sponges and sharps are counted at four points during a procedure. Instruments are routinely counted at which points?

    • A.Before the procedure begins and at the beginning of skin closure only
    • B.Only at the end of the procedure, when the field is broken down
    • C.Before the procedure begins and before closure of a body cavity✓ Answer
    • D.At the beginning of each closing layer and again at skin closure

    Instruments are counted before the procedure begins and again before a body cavity is closed, because an instrument is large enough that the realistic retention risk is inside a cavity rather than within a suture line, whereas sponges and sharps are counted at four points — before the incision, when closure of a cavity begins, when fascial closure begins, and as skin closure begins — since they can be retained in any layer. Additional counts are taken whenever items are added to the field and whenever scrub or circulating personnel are relieved. All counts are performed by the scrub and the circulator together, audibly and concurrently, with each item seen by both, and the specific policy is set by the facility.

    Source: AST Recommended Standards of Practice for Counts — count intervalsReport a problem with this question

16. 16. The closing sponge count is incorrect. What must be done FIRST?

    • A.Notify the surgeon immediately so that closure is not completed✓ Answer
    • B.Document the count as incorrect and allow the procedure to finish
    • C.Have the circulator search the trash and linen while closure continues
    • D.Recount everything on the back table before saying anything to the team

    The surgeon is informed at once because only the surgeon can stop or reverse closure and explore the wound, and every layer closed over a missing item makes retrieval more invasive for the patient. After notification, the scrub and circulator search the sterile and nonsterile field together — the field, the floor, under drapes, kick buckets, linen and trash — while the surgeon explores the cavity; if the item is still not found, an intraoperative radiograph is obtained before the patient leaves the room. An incorrect count is never accepted or dismissed, and the record must show the result, the measures taken to resolve it, and who performed the counts, according to facility policy.

    Source: AST Recommended Standards of Practice for Counts — incorrect count procedureReport a problem with this question

17. 17. During a long procedure, instruments on the Mayo stand are becoming coated with drying blood. What should the CST use to keep them clean at the point of use?

    • A.Sterile normal saline on a moist sponge
    • B.Sterile water, or an enzymatic product intended for point-of-use instrument care✓ Answer
    • C.An alcohol-based hand rub applied with a dry towel
    • D.Hot water carried in from the sub-sterile room

    Saline is avoided because its chloride ions attack the passive oxide layer of stainless steel and cause pitting and corrosion, which creates surfaces that harbor soil and cannot be cleaned. Hot water is also wrong because heat coagulates blood protein onto the instrument, making it far harder to remove during decontamination. Sterile water or an enzymatic product keeps blood and tissue from drying so that soil is removed later — and point-of-use care matters because an instrument that has not been thoroughly cleaned cannot be reliably sterilized, since soil shields microorganisms from the sterilant.

    Source: AST and AAMI guidance on point-of-use instrument care and decontaminationReport a problem with this question

18. 18. A delicate heat- and moisture-sensitive device with a long narrow lumen must be sterilized. Which consideration is MOST important in choosing the method?

    • A.Any low-temperature method may be substituted for any other low-temperature method
    • B.Steam is preferred because it is the least expensive method available
    • C.The device manufacturer's written instructions for use, which state the methods validated for that device✓ Answer
    • D.High-level disinfection may replace sterilization when the device has a lumen

    The manufacturer's written instructions for use are the authority because only the manufacturer has validated that a given process reaches every surface of that specific device without damaging it, and low-temperature methods are not interchangeable: hydrogen peroxide gas plasma cannot process cellulose, linen or paper and has restrictions on long narrow lumens, ethylene oxide penetrates well but requires prolonged aeration because of toxic residuals, and peracetic acid immersion produces an item that must be used immediately because it cannot be packaged or stored. A device that enters sterile tissue or the vascular system is a critical item, so high-level disinfection is not an acceptable substitute for sterilizing it. Choosing by cost or habit risks either an unsterile lumen or a destroyed instrument.

    Source: Spaulding classification and device manufacturer instructions for use in sterilization method selectionReport a problem with this question

19. 19. Why is immediate-use steam sterilization NOT an acceptable substitute for routine terminal sterilization?

    • A.It does not reach conditions capable of killing bacterial spores
    • B.The item is processed without protective packaging for direct transfer, so its sterility cannot be maintained or stored✓ Answer
    • C.It cannot be monitored with chemical or biological indicators
    • D.It may be used only for implants and never for standard instruments

    Immediate-use processing exists for an urgent, unplanned need — typically a single contaminated or one-of-a-kind instrument required right away — and the item is processed without a protective wrapper so that it can be delivered directly to the sterile field; with no barrier, there is nothing to maintain sterility over time or during storage and transport. It is monitored and it does reach sporicidal conditions, so those are not the objections; the objections are inadequate inventory, convenience, complete instrument sets, and routine implant processing. Cycle conditions vary with the load and the sterilizer and are set by the manufacturer's instructions.

    Source: AAMI guidance on immediate-use steam sterilization and its restricted indicationsReport a problem with this question

20. 20. A load containing an orthopedic implant has just completed a steam sterilization cycle. Before the implant is released for use, what should be verified?

    • A.That the package expiration date has not been passed
    • B.That the sterilizer printout shows the cycle ran to completion
    • C.The biological indicator result, because only a spore test demonstrates that the process was lethal✓ Answer
    • D.That the external indicator tape on the package changed color

    Only a biological indicator gives direct evidence of lethality, because it challenges the cycle with live, highly resistant spores — Geobacillus stearothermophilus for steam and hydrogen peroxide processes, Bacillus atrophaeus for ethylene oxide and dry heat — and shows whether they were actually killed. Implant loads should include a biological indicator and be quarantined until the result is read, because a retained implant infection is catastrophic and cannot be corrected without further surgery. External indicator tape is a process indicator that proves only exposure to a sterilizing process, and the printout is mechanical monitoring showing what the chamber conditions were, neither of which demonstrates that organisms died; documented emergency release using an integrating indicator is an exception, not the routine.

    Source: AAMI sterilization monitoring guidance — biological indicators and release of implant loadsReport a problem with this question

21. 21. During an elective procedure on an uninflamed, unopened surgical site, a major break in sterile technique occurs at the field. How is the wound MOST likely classified?

    • A.Class I, clean
    • B.Class IV, dirty-infected
    • C.Class III, contaminated✓ Answer
    • D.Class II, clean-contaminated

    A major break in sterile technique moves the wound into Class III, contaminated, alongside fresh open accidental wounds, gross spillage from the gastrointestinal tract, and incisions in which acute nonpurulent inflammation is found — the reasoning is that the wound has received a significant microbial load even though no established infection is present. Class I is a clean wound with no break and no entry into the respiratory, alimentary or genitourinary tract; Class II is one of those tracts entered under controlled conditions without unusual contamination; Class IV is an old traumatic wound with devitalized tissue or an existing clinical infection or perforated viscus. Accurate classification matters because it drives surgical site infection surveillance and the risk adjustment applied to the case.

    Source: CDC 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 →