
PDA Technical Glossary
PDA Technical Reports are highly valued membership benefits because they offer expert guidance and opinions on important scientific and regulatory topics and are used as essential references by industry and regulatory authorities around the world. These reports include terms which explain the material and enhance the reader’s understanding.
The database presented here includes the glossary terms from all current technical reports. The database is searchable by keyword, topic, or by technical report. Each definition provided includes a link to the source technical report within the PDA Technical Report Portal.
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Biological Qualification
A component of performance qualification that demonstrates, by use of biological indicators, that the required lethality (FBIO) is achieved consistently throughout the load. (TR1) (TR3) (TR30) A component of performance qualification that demonstrates, by use of biological indicators, that the required lethality (FBIO) or spore log reduction (SLR) is achieved consistently throughout the sterilized or sanitized portion of the SIP system. (TR61)
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Bracketing Approach
A scientific approach for defining product/load characteristics (e.g., viscosity, container sizes, container fill volumes, item sizes, loading configurations) that are tested (in a qualification study or validation study) at upper and/or lower limits. (TR1) (TR61) A validation method that tests the extremes of a process or product. The method assumes the extremes will be representative of all the samples between the extremes. (TR26)
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Cool-Down Phase
The phase of a sterilization cycle that occurs after completion of the exposure phase. Parameters of a cool-down phase are typically defined in order to meet applicable user requirements for load cooling and drying. (TR01) The phase of a sterilization cycle that occurs after completion of the exposure phase. [Synonym: post-conditioning phase, slow exhaust phase, drying phase, equalization phase] (TR48) The phase of an SIP cycle that occurs after completion of the exposure phase. Parameters (e.g., time, temperature, pressure) of a cool-down phase are typically defined in order to meet applicable user requirements for system cooling and drying. (TR61)
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DT Value
The time in minutes required for a onelogarithm, or 90%, reduction of the population of microorganisms used as a biological indicator under specified lethal conditions. For steam sterilization, the D-value should always be specified with a reference temperature, DT . For example, a BI system with a D121°C = 1.4 minutes requires 1.4 minutes at 121°C to reduce the population by one logarithm.(TR1) (TR61)
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F-Value (Lethality Factor)
A measurement of sterilization effectiveness, the F-value is the calculated equivalent lethality (using a specified z-value), in terms of minutes at a reference temperature (Tref), delivered by a sterilization cycle. (TR1) (TR3) (TR30) (TR48) (TR61)
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Gravity Displacement
A sterilization process based on the principle that cold air within the chamber is heavier than the steam entering and will sink to the bottom of the chamber. As steam enters the chamber, air is pushed out the bottom drain and exits, with the condensate, through a steam trap. (TR01) (TR48) (TR61)
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Heat-up Phase
The phase of a sterilization cycle that occurs prior to the exposure phase. Process parameters are developed for this phase in order to meet applicable user requirements for load conditioning (e.g., air removal and preheating.) (TR01) (TR3) (TR48) (TR61)
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Minimum Acceptable Cycle (MAC)
The minimum cycle conditions (in terms of delivered minimum lethality or minimum time and temperature) that would be considered acceptable. (TR01) (TR61)
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Operating Parameters (Key Parameters)
Values that are controlled and/or measured and are used to assure the ongoing “state of control” and consistency of runs. Failure to meet a key process parameter should result in an investigation with a documented rationale for the disposition of the load. (TR01) (TR3) (TR51) (TR48) Values that are controlled and/or measured and are used to assure the ongoing “state of control” of steam in place cycles. Failure to meet a key process parameter should result in an investigation. (TR61)
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Overkill Design Approach
A sterilization design approach where minimal information is required about the product bioburden. A worst-case bioburden assumption is used to determine the delivered lethality needed to achieve a PNSU of 10-6 on or in the items being sterilized. When using this approach, the qualification program must demonstrate that both the FBIO and FPHYS are greater than 12 minutes. The required lethality may vary regionally. (Note: For typical SIP systems, the FPHYS will need to be greater than the FBIO.) (TR01) (TR3) (TR30) (TR61)
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Saturated Steam
Steam that is at a temperature and pressure that corresponds to the vaporization curve of water. It is in a state of equilibrium between being a liquid and a gas, with no entrained liquid water. [Synonym: Dry Saturated Steam] (TR01) (TR48) (TR61)
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Steam: Pure Steam
Collected condensate that complies with the Compendial requirements for Water for Injecton (WFI). [Synonyms: clean steam, high quality steam] (TR01) (TR61) (TR48)
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Superheated Steam
Steam that is at a higher temperature than that indicated by the equilibration curve for the vaporization of water (at a given pressure).(TR01) (TR61)
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Survivor Curve
Graphical representation of the inactivation of a population of microorganisms with increasing exposure to a microbicidal agent under stated conditions. (TR01) (TR3) (TR51) (TR61)
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Z-Value
The number of degrees of temperature change necessary to change the D-value by a factor of 10. The z-value allows integration of the lethal effects of heat as the temperature changes during the heating and cooling phases of a sterilization cycle. (TR01) (TR3) The number of degrees of temperature change necessary to change the D-value by a factor of 10. The z-value allows integration of the lethal effects of heat over time (i.e., calculation of F0) as the temperature changes in a cycle. (TR61)