
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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- TR 15: Validation: TFF in Biopharmaceuticals (17)
- TR 26: Sterilizing Filtration of Liquids (11)
- TR 45: Depth Filtration (11)
- TR 41: Virus Filtration (10)
- TR 14: Validation: Protein Purification Chromatography (6)
- TR 22: Aseptic Process Simulation (5)
- TR 75: Mycoplasma Filter Rating Method (5)
- TR 62: Manual Aseptic Processes (4)
- TR 69: Bioburden/Biofilm Management (3)
- TR 1: Validation: Moist Heat (3)
- TR 47: Virus Spikes/Virus Clearance (2)
- TR 50: Alt. Methods Mycoplasma Testing (2)
- TR 60: Process Validation (2)
- TR 66: Single-Use Systems (2)
- TR 73: Prefilled Syringe User Requirements for Biotech Applications (2)
- TR 13: Environmental Monitoring (2)
- TR 28: Process Simulation for Bulk API (2)
- TR 30: Parametric Release (2)
- TR 77: The Manufacture of Sterile Pharmaceutical Products Using Blow-Fill-Seal Technology (2)
- TR 51: Biological Indicators (1)
- TR 54-4: QRM: Biotech Drug Substance (1)
- TR 61: Steam in Place (1)
- TR 70: Cleaning/Disinfection Programs (1)
- TR 74: Reprocessing of Biopharmaceuticals (1)
- TR 83: Virus Contamination in Biomanufacturing: Risk Mitigation, Preparedness, and Response (1)
- TR 88: Microbial Data Deviation Investigations in the Pharmaceutical Industry (1)
- TR 76: Identification and Classification of Visible Nonconformities in Elastomeric Components and Aluminum Seals for Parenteral Packaging (1)
- TR 42: Validation: Protein Manufacturing (1)
- TR 43: Glass Defects (1)
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- Manufacturing (52)
- Microbiology (29)
- Sterile Processing (21)
- GMP/Good Manufacturing Processes/cGMP (20)
- Packaging Science (18)
- Validation (14)
- Quality Risk Management/QRM (10)
- Virus (9)
- Combination Products (6)
- Supply Chain (6)
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- Prefilled Syringes/PFS (4)
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Acholeplasma laidlawii
A. laidlawii is a mycoplasma in class Mollicutes and order Acholeplasmatales. (TR75)
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Action Level (environmental monitoring)
An established microbial or non-viable particle level that, when exceeded, should trigger appropriate investigation and corrective action based on the investigation. (TR22)
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Action Limit
An internal (in-house) value used to assess the consistency of the process. The cause of the excursion should be investigated and documented and corrective action is generally required. Action limits are not specifications. (TR42)
An established internal (in-house) data-based value which is part of the control strategy and used to assess the consistency of the manufacturing process. An action limit excursion result in an investigation, identification of recovered isolates, root-cause analysis, assessment of a systemic failure and impact on product quality and patient safety. (TR69)
An established internal (in-house) data-based value that is part of the control strategy and used to assess the consistency of the manufacturing process. An action limit excursion result in an investigation, identification of recovered isolates, root-cause analysis, assessment of a systemic failure and impact on product quality and patient safety. (TR74)
A limit that, when exceeded, indicates a process is outside of its normal operating range. A response to such an excursion should involve a documented investigation and corrective actions based on the results of that investigation. (TR60)
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Aerobic Microorganism
A microorganism that utilizes oxygen as the final electron acceptor during metabolism; a microorganism that will grow primarily in the presence of oxygen. For the purpose of this report, this definition encompasses facultative anaerobes. (TR22) (TR62)
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Alert Level
An established microbial or nonviable particle level giving early warning of potential drift from normal operating conditions; not necessarily grounds for definitive corrective action but typically requires follow-up investigation. (TR13) (TR22) (TR69)
An established level that, when exceeded, is giving an early warning of a potential drift from normal operating conditions; while not necessarily grounds for definitive corrective action, it typically requires follow-up review. (TR 60)
An established microbial or nonviable particle level giving early warning of potential drift from normal operating conditions; not necessarily grounds for definitive corrective action, but typically requires follow-up investigation (3, 4, 7). (TR88)
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Anisotropic (Asymmetric) Membrane
A membrane in which the pore size and structure differ from one face to the other. These membranes are usually considered “directional” because of the difference in flow characteristics, depending on which surface of the membrane faces the feed stream. (TR15)
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Aseptic Processing
Handling sterile materials in a controlled environment, in which the air supply, facility, materials, equipment and personnel are regulated to control microbial and particulate contamination to acceptable levels. (TR28) (TR62) (TR69) Handling of sterile product, containers, and/ or devices in a controlled environment in which the air supply, materials, equipment, and personnel are regulated to maintain (product) sterility. (TR13)
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Aseptic Processing Area (APA)
Controlled environment, consisting of several zones, in which the air supply, facility, materials, equipment and personnel are regulated to control microbial and particulate contamination to acceptable levels. (TR22) (TR28) (TR62) (TR70)
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Aseptic Processing Simulation (APS)
A means for establishing the capability of an aseptic process as performed using a growth medium. (TR22) (TR62)
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Autoclave
A chamber for steam sterilization. (TR45)
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Back Pressure
Residual pressure opposing the free flow of liquid or gas at the outlet side of the filter. (TR45) Pressure applied downstream of a filter or other piece of equipment. (TR26)
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Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. The term is commonly used in its shortened form, “phage”. (TR41) (TR 47)
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Batch Filtration Process
In a batch filtration process, the entire volume to be filtered is held in a single feed tank. The retentate stream is recycled back to that single feed tank. (TR15)
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Bracketing
A demonstration of unit operation performance at two different values of a given parameter (e.g., ionic strength, dwell time or temperature), allowing the use any values of that parameter falling within this range. (TR41)
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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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Breakthrough Limited
A filtration operation resulting in a significant rise in filtrate turbidity accompanied by a small increase in differential pressure. This occurs when the adsorptive capacity of the filter is reached, resulting in the passage of particles smaller than the pore size of the filter that would normally be removed by adsorption. (TR45)
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Brevundimonas Diminuta (B. diminuta)
Small bacteria (0.3–0.4 &mum in diameter by 0.6–0.1 &mum long) used to challenge a sterilizing grade filter during validation testing. [Formerly Pseudomonas diminuta](TR45)
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Bubble Point
The measured differential gas pressure at which a wetting liquid (e.g., water, alcohol, product) is pushed out of the largest pores of a wetted porous membrane, and a steady stream of gas bubbles or bulk gas flow is detected.(TR15) (TR26) The minimum pressure at which a wetting liquid is pressed out of the pore system of a membrane while forming a steady bubble chain. (TR41)
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Cake
Solids deposited on the upstream side of filter media. (TR15) (TR45) (TR26)
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Challenge Concentration
The concentration in Colony Forming Units/mL of the test microorganism in the challenge fluid. (TR75)
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Challenge Level
The concentration of the test microorganism applied to the test filter (per centimeter squared) or the total number of cells applied to the test filter at the completion of the challenge. (TR75)
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Challenge Volume
The volume of challenge fluid applied to the test filter. (TR75)
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Chemical Compatibility
The relative stability of filter materials and/or filter assembly components when exposed to process fluids and process parameters. (TR45)
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Chemical Indicator
Test system that reveals change in one or more predefined process variables based on a chemical or physical change resulting from exposure to a process. (TR01) (TR30)
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Chemical Integrator
A device that is designed to react in a quantitative manner to multiple sterilization variables, (typically, time and temperature and, in some instances, moisture). (TR01) (TR30)
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Clarification
The removal of solid particulates from a liquid through filtration, sedimentation, centrifugation or other means. (TR45)
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Column Load
The solute that is passed through the column for separation. (TR14)
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Column Packing
Preparation of a column that includes the addition of resin slurry into a column to create a bed suitable for its intended use. Characteristics of a packed column bed include bed height and diameter, backpressure, and number of theoretical plates. (TR14)
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Compatibility (Filter)
The ability of a filter to be used with a particular process fluid without a change in the inherent properties of the filter. (TR41)
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Consumables
This refers to items (e.g., SUS, storage bags, tubing, filters, diaphragms, flasks, etc.) that form or are a part of process equipment and are used on a per batch basis. (TR66)
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Cross-Flow Rate
Volumetric rate of fluid flow parallel to the membrane surface. (TR15)
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Diavolume (DV)
A volume equal to the retentate volume to which a diafiltration buffer is added. (TR15)
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Differential Pressure
The difference in pressure between the upstream (feed or influent) and downstream (effluent) sides of the filter. (May be modified with the terms: applied, available differential pressure, clean differential pressure, dirty differential pressure, initial differential pressure, or maximum differential pressure). [Synonym: Delta P (Δ P), PSID, Pressure Drop] (TR45) (TR26)
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Diffusion Flow Test
A test to determine the integrity of a filter. The test is based on the measurement of the diffusive (diffusional) flow of a gas through a wetted filter, along with any bulk flow of gas through open (unwetted) pores. Either the gas flow or the downstream liquid, displaced by the gas flow, may be measured. [Synonym: Forward Flow Test] (TR45)
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Diffusion Test (or Forward Flow Test)
A test for membrane integrity that involves measuring the rate of gas diffusion through a liquid-wetted membrane.(TR15) An integrity test in which a filter is subjected to differential gas pressures below the bubble point and gas molecule migration through the water-filled pores of a wetted membrane is measured. This behavior follows Fick’s Law of Diffusion (i.e., the gas diffusional flow rate for a filter is proportional to the differential pressure and the total surface area of the filter). (TR41)
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Diffusive/Forward Flow Test
A test to determine the integrity of a filter. [Synonym: diffusive flow test, forward flow test.] (TR26)
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Dimensional Product Quality
The product conforms to the required drawing dimensions. (TR43)(TR76)
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Direct Flow Filtration (DFF) or Normal Flow Filtration (NFF)
In direct flow filtration, all fluid is directed through the membrane in a single pass. (TR41)
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Downstream Side (of Filter)
The effluent side of the process step (filter). (TR45) The filtrate or outlet side of the filter. (TR26)
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Elastomer
Thermoplastic material formulation (that may or may not contain rubber/natural latex) derived from elastic polymer; often used interchangeably with the term “rubber.” (TR73)
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Eluate
Solution (effluent) that flows out of the chromatographic column containing the drug substance. [Synonym: collected product fractions] (TR14)
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Elution
Desorption of a drug substance from a chromatographic column. (TR14)
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Fed-Batch Filtration Process
A modification of the batch filtration process in which a separate (typically larger) reservoir feeds a smaller recycle tank. The retentate stream is returned to the recycle tank. (TR15)
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Feed
The starting solution prior to filtration. (TR15)
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Feed (or Load or Feedstock or Feedstream)
The fluid introduced into a process. (TR41)
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Feed Pressure
The pressure measured at the inlet of the tangential flow filter device. (TR15)
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Filter
A porous medium used for the separation of components in a fluid stream.(TR15)
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Filtrate
Fluid that has been passed through a process step (filter). [Synonym: Permeate] (TR15) (TR26)
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Filtration
A process of removing particles from a fluid by passing it through a permeable material, such as a membrane film. (TR41) The process by which particles are removed from a fluid by passing the fluid through a porous material. (TR26)
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Flow Decay Test
An experiment to determine flow rate and throughput of a filter type or combination of filters on a specific liquid, usually by using a small area filter, to determine the sizing of a filter system by extrapolation. (TR45)