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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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Electronic Health Record (EHR)

Digitized patient records that include medical history, diagnoses, medications, treatment plans, immunization dates, allergies, radiology images, and laboratory test results. This information supports mor effective treatment when patients switch healthcare providers due to new therapies, re-location, or for epidemiological research and predictive health analytics.

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HETP (Height Equivalent to the Theoretical Plate)

A measurement of column packing efficiency or integrity, calculated from the column height divided by the number of theoretical plates. (TR14)

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Half-Cycle Qualification

A qualification method that uses fifty percent of the exposure time to demonstrate sterilization cycle efficacy. The physical and biological lethality values achieved in the half-cycle exposure time are doubled to project the lethality that will be achieved by the full cycle.(TR01)

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Hallucination

Instances where AI systems, particularly those based on advanced models like GPT-4, generate outputs that are incorrect, misleading, or nonsensical, despite displaying high confidence. Hallucinations can result from biases in the training data, model limitations, or inherent uncertainties in the problem space.

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Harm

Damage to health, including damage occurring from loss of product quality or availability. (TR44) (TR54) (TR54-2) (TR54-4) (TR68)

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Hazard

The potential source of harm. (TR44) (TR54) (TR54-2) (TR58) (TR61)

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Hazard Analysis and Critical Control Points (HACCP)

A systematic, proactive, and preventative tool for assuring product quality, reliability, and safety (TR54-3) (TR54) A management system in which potential hazards are addressed through the identification and control of key risk factors (critical control points) of the biological, chemical, and physical hazards from raw material production, procurement and handling, to manufacturing, distribution and consumption of the finished product. (TR55)

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Hazard and Operability Analysis (HAZOP)

A structured, systematic and qualitative technique for examination of a planned or existing process or operation in order to identify and evaluate problems that may represent risks to personnel or equipment, or prevent efficient operation. (TR54)

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Hazardous Situation(s) [Cause(s

Circumstances in which people, property, or the environment is exposed to a hazard. (TR54-2)

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Health Hazard Evaluation (HHE)

A tool for classifying a voluntary recall by a firm. The HHE guides the US FDA in determining the risk to the public from the defective product and appropriate actions for the firm and the FDA to take to protect public health. (TR55)

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Health Informatics

The intersection of information science, computer science, and healthcare that involves the use of technology to store, manage, and analyze health-related information.

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Heat Transfer

Energy that is transferred as a result of a temperature difference between an object and its surroundings. (TR48)

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Heat-Treated Wood Pallets

Two types of methods to include kiln drying versus steam heat. (TR55)

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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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Heating, Ventilating, and Air-Conditioning (HVAC)

Refers to technology of indoor and automated environmental control. (TR70)

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Hemadsorption

Adherence of red blood cells to virus-specific antigens on the surface of infected cells. In cellbased in vitro assays the reaction is used as an end point for virus detection. (TR47) (TR71)

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Hemagglutination

A clumping together or agglutination of red blood cells. In the context of this Technical Report hemagglutination indicates presence of virus that binds to erythrocytes. (TR47) The clumping of red blood cells by binding to virus particles. The hemagglutination reaction is used in cell-based in vitro assays as an end point for virus detection. (TR71)

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High-Efficiency Particulate Air (HEPA) Filter

A type of air filter that must satisfy certain standards of efficiency such as those set by the United States Department of Energy (DOE). The air filter must remove 99.97% of all particles greater than 0.3 micrometer from the air that passes through it. (TR62) (TR70)

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Highly Hazardous Drug Active

A drug active that can cause serious adverse effects at typical doses. Those adverse effects are generally not related to the main therapeutic activity of the drug, and includes effects such as carcinogenicity, mutagenicity, genotoxicity, reproductive hazards, allergenicity, and cytotoxicity. (TR29)

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Historian

A type of database designed to archive automation and process data. (TR84)

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Historical Data

For purposes of this guidance, data on impurities or physical attributes from three or more consecutive, representative pre-modification batches. (TR38)

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Hold-Up Volume (Residual Volume, Nonexpellable Volume, Dead Volume)

Amount of fluid remaining in the syringe when the plunger has reached the end of travel within the barrel. (TR73)

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Host Cells/Parental Cells

A non-transfected cell substrate that is generally well-characterized and banked. It can be manipulated to generate a cell substrate for production of a biological medicinal product. (TR83)

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Human Factors

A science discipline that examines human psychological, social, physical, and biological characteristics to evaluate the design, operation, or use of products or systems for optimizing human performance, health, safety, and/or habitability. [Synonym: Ergonomics] (TR62)(TR80)

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Human-in-the-Loop (HITL)

Human-in-the-Loop (HITL) is a capability and role whereby qualified personnel can meaningfully intervene within the system’s decision cycle during operation or oversight activities or to enhance trust and continuous improvement. These actions are in place to address uncertainty and limitations, override or adjust outputs, and provide feedback that supports continuous performance assurance. Professionals can actively guide, review, and verify the AI output. HITL is applied in a risk-based manner, with the level and timing of oversight, controls, and documentation proportionate to the system’s intended use and risk and evaluated on the performance of the human–AI team, not the model alone.

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Hybrid Approach (WHO)

The use of a computerized system in which there is a combination of original electronic records and paper records that comprise the total record set that should be reviewed and retained.(TR80)

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Hybrid Model

A computational model that combines elements from multiple modeling approaches, such as empirical, mechanistic, and machine learning techniques, to solve complex problems. By leveraging the strengths of each approach, hybrid models enhance predictive accuracy, robustness, and interpretability. Applications include integrating mechanistic drug metabolism models with machine learning algorithms trained on experimental data to predict the pharmacokinetic behavior of new drug candidates. Similarly, hybrid models can merge empirical data with physiological knowledge to simulate drug-disease interactions or optimize formulation designs.

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Hybridization

The formation of a double-stranded complex of complementary strands of nucleic acids (e.g., a primer and single-stranded DNA or RNA) (TR50)

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Hydraulic Pressure

Pressure that results from forcing liquid through an orifice, pipe or other channel. (TR45)

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Hydrophilic

Literally “water loving.” A filter that will wet with aqueous solutions to allow flow at a low pressure differential. (TR26)

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Hyperparameter Tuning

The process of optimizing the configuration settings (hyperparameters) of a machine learning model to maximize performance. Proper tuning prevents underfitting and overfitting, improving overall accuracy.