Bioindicator test and/or equilibration time: is meeting one of both enough in some cases?

Hi all,

Which of the following scenarios is possible? Is one (or both) acceptable?

Setup: one puts a thermocouple and bioindicator in close proximity inside a load item (e.g. tube), and you get one the following results (lets say standard sterilization cycle, 25 minutes):

  • You equilibration time is met (0 seconds), but the bioindicator is not inactivated. (Is this actually possible?)
  • Your bioindicator is inactivated, but the equilibration time was not met (higher than 30 seconds).

Bioindicators alone required for US market (FDA requirement)?
Equilibration time alone required for EU market (EN 285 requirement)?


I’m would be surprised if you have a passing equilibration time (but zero seconds, for all probes, even in an item?) and a failed bio-indicator. I would think this scenario would be caused by a lack of steam, which is caused by air entrapment typically. But again, this air entrapment is intended to be tested out using the equilibration time requirement.

I’m not surprised that you have a passing bio-indicator, but a failed equilibration time. This can easily be caused by heavy/dense mass that takes some time to come to temperature, but which eventually gets to temperature and then gets killed with a long enough sterilization hold time.

With the ICH push (to harmonize everything) I wouldn’t shoot for just US, or just EU criteria. I would push for both, even if the target market is just one or the other.

I would use Bioinidicators for all cycles (except pourous loads as discussed on other topics in here). I would also require that EN 285 for equilibration time is met.

My personal opinion is that equilibration time is good, but a cycle can hide equilibration time, and so is not as useful as BioIndicators. But that is my opinion and I realise that the regulatory boards don’t all agree with my opinion, and so I happily follow what is required.