DHA Central Sterile Services Technician exam questions

6 worked Central Sterile Services Technician practice questions

Original exam-style questions from the bank, spread across the blueprint domains. They are not real or recalled exam questions. Try each one, then open the answer for the rationale and reference. None of them appear in the free mock exam, so reading them will not spoil it.

1. Question 1 · Decontamination: Cleaning and Disinfection

   A washer-disinfector thermal stage must achieve an A0 of 3000 for items contaminated with heat-resistant viruses. Which time and temperature gives this value?

   1. A90 degrees Celsius for 5 minutes
   2. B80 degrees Celsius for 1 minute
   3. C70 degrees Celsius for 10 minutes
   4. D60 degrees Celsius for 30 minutes
   Show answer and explanation

   Correct answer: A. 90 degrees Celsius for 5 minutes

   An A0 of 3000 corresponds to 90 degrees Celsius held for 5 minutes. An A0 of 600, used for lower-risk items, equals 80 degrees Celsius for 10 minutes.

   Reference: ISO 15883-1: Washer-disinfectors, General Requirements

2. Question 2 · Inspection, Assembly and Packaging

   During inspection under lighted magnification, dried blood is found in the box joint of a clamp. What should be done?

   1. ADiscard the whole set
   2. BWipe it with alcohol and package it
   3. CPackage it, as sterilisation will kill microbes
   4. DReturn it for decontamination
   Show answer and explanation

   Correct answer: D. Return it for decontamination

   Any instrument with visible soil must be returned to decontamination and recleaned before packaging. Sterilisation cannot be relied on to penetrate soil.

   Reference: AAMI ST79: Comprehensive Guide to Steam Sterilization in Health Care Facilities

3. Question 3 · Inspection, Assembly and Packaging

   Why is an internal chemical indicator placed inside every package?

   1. ATo record the steriliser number
   2. BTo prove the contents are sterile
   3. CTo show sterilant reached the contents
   4. DTo replace the biological indicator
   Show answer and explanation

   Correct answer: C. To show sterilant reached the contents

   An internal chemical indicator shows that the sterilant conditions reached the inside of the pack. It does not prove sterility, and it does not replace biological monitoring.

   Reference: AAMI ST79: Comprehensive Guide to Steam Sterilization in Health Care Facilities

4. Question 4 · Low-Temperature Sterilisation

   A hydrogen peroxide low-temperature cycle repeatedly aborts with a load of flexible instruments. What is the most likely cause?

   1. AUsing polypropylene wrap
   2. BResidual moisture in the load
   3. CPlacing a chemical indicator inside
   4. DItems that are heat-sensitive
   Show answer and explanation

   Correct answer: B. Residual moisture in the load

   Residual water in lumens or on surfaces makes it hard to reach the required vacuum and commonly causes cycle cancellation, so items must be completely dry. Polypropylene wrap is compatible, and heat-sensitive items are the reason for using this method.

   Reference: AAMI ST58: Chemical Sterilization and High-level Disinfection in Health Care Facilities

5. Question 5 · Microbiology and Infection Prevention Principles

   Neurosurgical instruments have been used on brain tissue of a patient later suspected of having Creutzfeldt-Jakob disease. What is the correct handling while the diagnosis is pending?

   1. AHigh-level disinfect them and reuse
   2. BProcess them in a routine steam cycle
   3. CQuarantine and do not reuse them
   4. DClean them and send them to the ward
   Show answer and explanation

   Correct answer: C. Quarantine and do not reuse them

   Prions resist standard processing, so instruments used on high-risk tissue in a suspected case are quarantined until the diagnosis is known and incinerated if confirmed. Routine processing does not reliably inactivate prions.

   Reference: WHO Infection Control Guidelines for Transmissible Spongiform Encephalopathies 1999

6. Question 6 · Monitoring, Quality Assurance and Traceability

   A biological indicator from yesterday's steam load is positive. Which loads should be recalled?

   1. AOnly the load containing the positive BI
   2. BAll loads since the last negative BI
   3. COnly implant loads from today
   4. DNo loads, if the chemical indicators passed
   Show answer and explanation

   Correct answer: B. All loads since the last negative BI

   A positive BI means sterility cannot be assured, so all loads processed since the last negative BI from that steriliser are recalled and quarantined while the cause is investigated. Passing chemical indicators do not override a positive BI.

   Reference: AAMI ST79: Comprehensive Guide to Steam Sterilization in Health Care Facilities