When the method is precisely the same as described on the Certificate, you can compare the results with the property value on the Certificate of Analysis. Another technique, media, or incubation temperature, can give other effects and can provide another result.

Checklist for root cause analyses:

1. Media – the most common cause of differences

Check if the used media and possibly used filters fit your purpose. Therefore, performance testing of culture media according to ISO 11133 and performance testing of membrane filters according to ISO 7704 can be performed.

Search on the BiosistoStandard, which controls must be used as a minimum.

2. Incubation

Check the incubation temperature and time to see if they are correct.
Some microorganisms are sensitive to temperature. If the temperature of an incubator is set just a little too high, this can result in no growth

3. Used equipment

Check if the used equipment is fit for the purpose. For example, is the pipette calibrated?

4. frequency

How often does this problem occur? Is this structural, or is it an incident issue?

5. Comparison with other labs

How do your results compare with other laboratories? An easy way to compare your results with other laboratories is to use the BiosistoChart. Ask for a free account


If you cannot find a cause for the deviating CRM value as a result of the above questions, please do not hesitate to contact Biosisto.


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