STAT 509 Lesson 3: Overview of Clinical Trial Designs

Comprehensive flashcards covering clinical trial design principles, study types, bias control, trial phases, and protocol management based on Lesson 3 notes.

Clinical Trial Design Origin

Originated in agricultural research, then influenced laboratory and industrial research before being applied to pharmaceutical trials in humans.

Control (Experimental Design Feature)

Management of the experimental process to reduce experimental error.

Replication (Experimental Design Feature)

Repetition of experimental units to provide information about variability and estimate response variability.

Randomization (Experimental Design Feature)

The assignment of treatments by chance to remove systematic error/bias and justify Type I error probabilities.

Human-response variability

Medical treatment responses generally vary more than responses in genetically identical plants/animals or tightly controlled physical/chemical experiments.

Ethics in Clinical Design

Paramount considerations that constrain what can be controlled, assigned, or measured in human research.

Patient Accrual and Follow-up

Precision requirements often necessitate long periods of recruitment and follow-up where subjects do not all enter on the same day.

Participant Withdrawal

A feature where volunteers choose to stop participating, which is generally not present in classical laboratory experiments.

Inaccuracy (Bias)

A major shortcoming of poor trials involving systematic errors in estimated treatment effects.

Imprecision

A major shortcoming of poor trials characterized by large variability in estimated treatment effects.

Clinical Trial Objective

Estimating the magnitude of treatment effects or differences between treatment effects.

Internal Validity

The assurance that an observed difference between study groups is real rather than caused by bias, chance, or confounding.

External Validity

How well results from a human trial generalize to a broader population.

Case Report

An uncontrolled observational report demonstrating that a clinical event is possible, primarily used to generate hypotheses.

Case Series

A collection of related cases that cannot establish treatment efficacy and is highly susceptible to selection bias.

Laetrile Case-Series Lesson

A historical example where multiple case series suggested cancer efficacy, but rigorous controlled testing failed to support it and revealed cyanide toxicity.

Database Analysis

Secondary analysis of an existing database to explore patterns and generate hypotheses; frequently biased if treatment was chosen by physicians rather than randomized.

Case-Control Study

A comparative observational study where investigators select cases with disease and controls without disease, then retrospectively assess prior exposure.

Recall Bias

Systematic differences in the accuracy or completeness of participants' recall of past exposures or events.

Prospective Cohort Study

An observational study where individuals are followed forward in time to relate baseline risk factors to subsequent outcomes.

Residual Confounding

A state in cohort studies where non-randomized covariates remain confounded with the factor of interest despite analysis efforts.

Controlled Clinical Trial

An experimental design where treatments are assigned by design and administration is governed by a protocol.

Experimental Unit

The unit randomized to a treatment regimen and receiving the treatment directly.

Observational Unit

The unit on which measurements are taken; in clinical trials, it is usually the same as the experimental unit.

Community Intervention Trial

A trial where communities or geographic regions are randomized (experimental units) while outcomes are measured on individuals (observational units).

Factor

A variable controlled and varied during an experiment, such as treatment.

One-way Design

A study design involving only one factor, typical of many clinical trials.

Two-way Factorial Clinical Trial

A trial studying combinations of levels of two factors, such as doses of two different chemotherapeutic agents.

Parallel Design

A design where patients are randomized to one treatment and remain on it throughout the trial.

Crossover Design

A design where patients are randomized to a sequence of treatments and switch from one to another over separate time periods.

Washout Period

A period between crossover treatments meant to reduce residual effects from the previous treatment.

Carry-over Effect

The residual effect of a treatment from an earlier period that influences a subject's response during a later treatment period.

Selection Bias

Systematic treatment-assignment differences caused when the type of patient receiving one treatment differs from those receiving another.

Blocking

A restriction of randomization designed to balance treatment assignments after a prescribed number of randomizations.

Stratification

Dividing participants into groups based on an important characteristic and randomizing within those groups to control unwanted variation.

Placebo Effect

Improvement caused by a patient's expectation of a positive response rather than an active treatment effect.

True Placebo

An inert/inactive treatment that mimics the route and appearance of the active treatment, such as a sugar pill.

Active Control

The use of an accepted therapy as the comparison group when using a placebo is unethical due to serious illness.

Sham Surgical Procedure

A procedure intended to mimic surgery as a placebo control.

Treatment Masking / Blinding

Keeping treatment identity hidden to preserve objectivity, especially for subjective outcomes.

Double-masked Trial

A trial where both investigators and patients are masked to the treatment assignment.

Confounding

The effect of other relevant factors on an outcome being incorrectly attributed to the difference between study groups.

Large Simple Trial

A trial enrolling large numbers with simplified management to detect small treatment advantages that matter to a large population.

Pragmatic Trial

A trial emphasizing treatment effectiveness in ordinary practice outside of academic medical centers.

Superiority Trial

A comparative study aiming to demonstrate that a new treatment is better than a control.

Noninferiority Trial

A trial aiming to show a new treatment is not worse than an accepted treatment by more than a prespecified margin.

Equivalence Trial

A study aiming to show commonality by keeping responses within prespecified margins in both directions relative to a comparison treatment.

Phase 0

Preclinical testing in animals to obtain pharmacokinetic information.

Phase I Trial

Small studies in humans investigating dose levels, safe dosage ranges, and common side effects.

Maximum Tolerated Dose (MTD)

A dose-finding target representing the highest dose that can be tolerated within the study safety framework.

Phase II Trial

Studies of preliminary efficacy and safety monitoring, often in patients with the disease of interest; may involve up to several hundred patients.

Phase III Trial

Rigorous randomized multi-center trials with control groups and definitive clinical endpoints used to demonstrate safety and efficacy for marketing approval.

Phase IV Trial

Post-approval expanded-safety research conducted to detect rare side effects and interactions in large populations (often $> 10,000$ patients).

Treatment Mechanism (TM) Trial

An early-stage study investigating treatment mechanisms, such as drug bioavailability or operative procedures.

Dose-finding (DF) Trial

An early-stage study seeking a specific dose, such as the maximum tolerated dose or minimum effective dose.

Safety and Efficacy (SE) Trial

A typical middle-stage study focusing jointly on safety and evidence of efficacy (Phase II).

Comparative Treatment Efficacy (CTE) Trial

A Phase III-type trial using controls to obtain precise estimates of clinical-outcome differences attributable to investigational therapy.

Expanded Safety (ES) Study

A large post-development safety study capable of identifying safety information not apparent in earlier trials (Phase IV).

Translational Study

A study whose primary outcome is a biological measurement or target derived from a model, often validating a compound's mechanism of action.

Prevention Trial

A study testing whether an intervention prevents disease onset, progression, or additional episodes.

Gold Standard

The reference diagnostic method assumed to be perfectly accurate for comparison in diagnostic trials.

Protocol

The document specifying the research plan and serves as the single most important quality-control tool for a clinical trial.

Protocol Violation

A departure from the planned protocol, which can result from differences in interpretation, carelessness, or unforeseen circumstances.

Manual of Operations (MOP)

A detailed operational document providing more specific instructions than the protocol for measurement and completion of data forms.

SPIRIT Statement

An international initiative providing a checklist of minimal elements for clinical-trial protocols.