Quick answer: A failed biological indicator means the spore population survived the cycle, so the load cannot be released. Before you re-sterilize, work through three confirmation steps: verify the control reader, check that the indicator and incubator settings were correct, and confirm the test pack was in the right position. Only then decide between a retest of the same load condition or removal of the sterilizer from service. Rushing straight to re-sterilization hides the cause and means the failure will repeat.
What does a failed biological indicator actually tell you?
A biological indicator carries a known population of resistant spores. After incubation, a colour or fluorescence change in the indicator means those spores were not killed. That is a direct statement about the lethality of the cycle, not a hint. A failed result means the process did not deliver the kill it was supposed to deliver.
The consequence is immediate: the load is not sterile and must not be released. Instruments either go back through a validated cycle after the cause is understood, or they are held. Releasing a load with a known failed indicator is the single most serious sterilization documentation error a clinic can make.
Step one: was the control indicator read correctly?
Every batch of biological indicators should be run with a control. The control is an unprocessed indicator from the same lot, incubated at the same time and temperature. It must show positive growth. If the control does not grow, the incubator or the lot itself is suspect, and a failing test indicator may be meaningless.
Record the control result on the same log line as the test. An entry that shows a test failure without a control result is not evidence of anything, and an inspector will treat it as an incomplete record.
Step two: were the indicator and incubator used correctly?
Read the packet. Incubation temperature matters — most steam indicators incubate in a narrow band around 56 to 60 C. An incubator running below the band can slow the change so a passing indicator looks inconclusive, while a unit running hot can stress the spores. Confirm the incubator set point against its display and, if you have a reference thermometer, verify it.
Then check the lot. An indicator stored above the recommended temperature, or used past its expiry, is not a valid test. Note the lot number and expiry on the log so this check is possible later.
| Check | What to confirm | If it fails |
|---|---|---|
| Control indicator | Positive growth from the same lot | Do not treat the test result as valid; investigate the lot or incubator |
| Incubation | Temperature inside the maker's band, correct duration | Re-run the test with a verified incubator |
| Indicator lot | Not expired, stored within range | Discard the lot and retest with a new one |
| Test pack position | Drain-side, per the maker's instructions | Re-run with a correctly placed pack |
| Cycle record | Time, temperature and pressure within the validated cycle | Treat as a cycle deviation and investigate |
Step three: was the test pack in the right place?
Position is the most overlooked cause. A pack placed against the chamber door or on top of a dense instrument set sees a different sterilant profile than one placed where the maker specifies. If the position was wrong, the failure may say more about the test than about the load.
Once all three steps pass but the indicator still fails, the balance of probability shifts to the sterilizer. At that point remove the unit from service, keep the failed indicator and the cycle record, and arrange a service call. Re-running the same load on the same machine without a fix is not a corrective action.
What should be recorded after a failed indicator?
The record should show the date, the sterilizer, the cycle number, the indicator lot and expiry, the control result, the incubation details, the action taken, and the outcome of the retest. That sequence is what converts a failure into a closed corrective action rather than an open question.
A clinic that can produce that record for every historical failure is in a strong audit position, because it demonstrates that the monitoring system detected a problem and the team responded. The absence of any recorded failures over years is, by contrast, a signal that monitoring may not be happening at all.
Related reading
Sterilization compliance hub; spore test incubation and failed results; spore test log fields; 24-hour biological indicators; BI 5-pack trial; sterilization monitoring collection.
Download the failure and retest record template from the compliance log centre, run the sterilization self-check to see whether your incubator checks are documented, and book a sterilization compliance consultation if you need help closing a corrective action.
Ordering for a clinic, lab or care home? Wholesale and multi-site ordering covers case pricing and account setup, and the B2B wholesale collection lists the lines stocked for institutional buyers. Reselling? become a distributor.
Frequently Asked Questions
Can I release a load if the biological indicator is only slightly off?
No. Any failure is a failure. The load is not sterile and must be held until the cause is understood and the instruments are reprocessed correctly.
Why does the control indicator matter?
The control proves the lot and the incubator can grow. Without a positive control you cannot tell whether a test failure reflects the cycle or a problem with the indicator itself.
What incubation temperature do steam biological indicators use?
Most steam indicators incubate in a narrow band around 56 to 60 C. Check the maker's instructions for your specific product and verify the incubator set point.
How many failed indicators justify a service call?
One unexplained failure after the three confirmation steps is enough to remove the unit from service and arrange an inspection.
CliniEco Medical is a licensed medical device establishment (MDEL #35334).
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