D Value / Population

D Value testing determines the resistance of a biological indicator (or other test sample) with a known population of microorganisms to a stated dose of sterilant.  Biological indicators are well-characterized preparations of a specific microorganism at a known population level and a known resistance to a specific sterilization process. This testing information is critical when selecting biological indicators to be used in the validation of sterilization processes and in monitoring routine sterilization cycles for the release of product.

There are a number of different formulae used to calculate the D value of a particular lot of biological indicators based on either fraction negative methods or a determination of the surviving population following exposure. These tests may be conducted on commercially prepared biological indicators to verify label claims, inoculation onto various substrates/devices or organism isolates. iuvo has qualified steam and Ethylene Oxide BIER vessels to perform exposures.


USP 55

Population per strip

D Value – USP, Current Supplement Spearman-Karber Method

D Value – Survivor Curve Method

D Value – Survival and Kill Analysis for Biological Indicators (ISO 11138-1)

D Value – Survival and Kill Analysis for Biological Indicators

D Value – Stumbo, Murphy, Cochran (SMC) Method

D Value – Limited (USP) Spearman-Karber (LS-K) Method