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Related Concept Videos

Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches01:23

Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches

Biopharmaceutical studies constitute a vital field aiming to enhance drug delivery methods and refine therapeutic approaches, drawing upon diverse interdisciplinary knowledge. In research methodologies, the choice between controlled and non-controlled studies significantly influences the study's reliability and accuracy.
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
Blinding01:11

Blinding

Blinding is a commonly used method of not telling participants which treatment a subject is receiving. Blinding is a critical part of a randomized control trial or RCT. It reduces the bias that affects the results. In an RCT, blinding is used in the form of a placebo. A placebo effect occurs when untreated subjects falsely believe they have received the treatment and report improved symptoms. A placebo or a dummy treatment is administered to subjects to negate the bias caused by such an effect.
Confounding in Epidemiological Studies01:27

Confounding in Epidemiological Studies

Confounding in statistical epidemiology represents a pivotal challenge, referring to the distortion in the perceived relationship between an exposure and an outcome due to the presence of a third variable, known as a confounder. This variable is associated with both the exposure and the outcome but is not a direct link in their causal chain. Its presence can lead to erroneous interpretations of the exposure's effect, either exaggerating or underestimating the true association. This phenomenon...
Bias in Epidemiological Studies01:29

Bias in Epidemiological Studies

Biases can arise at various stages of research, from study design and data collection to analysis and interpretation. Recognizing and addressing these biases is essential to ensure the validity and reliability of epidemiological findings.Broadly speaking, biases in epidemiology fall into three main categories: selection bias, information bias, and confounding. A more detailed description of possible biases is:
Bioequivalence Experimental Study Designs: Completely Randomized and Randomized Block Designs01:20

Bioequivalence Experimental Study Designs: Completely Randomized and Randomized Block Designs

Bioequivalence experimental study designs are crucial methodologies used in evaluating and comparing the bioavailability of different drug products. These designs are categorized into various types: completely randomized, randomized block, repeated measures, cross and carry-over, and Latin square designs.Completely randomized designs involve randomly allocating treatments to all subjects participating in the experiment. This allocation is achieved by assigning unique random numbers to subjects...
Study Designs in Epidemiology01:20

Study Designs in Epidemiology

Epidemiological study designs are fundamental tools for investigating the distribution, determinants, and control of health conditions in populations. They help researchers understand the relationships between exposures and outcomes, and they broadly fall into two categories: "observational" and "experimental" studies.
Observational studies are those where the researcher does not intervene but rather observes natural variations. They include cross-sectional, cohort, and case-control studies.

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Related Experiment Videos

Many multicenter randomized controlled trials do not account for center effect: a methodological review.

Mohamad Ossman1, Primael Megninou1, Florian Lejeune1

  • 1Sorbonne Université, INSERM, Institut Pierre Louis d'Épidémiologie et de Santé Publique, UMR-S 1136, AP-HP, Hôpital Pitié-Salpêtrière, Département de Santé Publique, Paris, France.

Journal of Clinical Epidemiology
|June 30, 2026
PubMed
Summary
This summary is machine-generated.

Few recent multicenter randomized controlled trials adequately address center effects in randomization and statistical analysis. Subgroup analyses by center are rarely performed, impacting the reliability of medical intervention evaluations.

Keywords:
Multicenter randomized controlled trialcenter effectsmethodologyrandomizationstatistical analysis

Related Experiment Videos

Area of Science:

  • Clinical Trials Methodology
  • Biostatistics
  • Health Services Research

Background:

  • Multicenter randomized controlled trials (RCTs) are crucial for evaluating medical interventions.
  • Center effects, variations in outcomes across different study sites, pose methodological challenges in multicenter RCTs.
  • Standardization and appropriate statistical handling of center effects are essential for robust trial results.

Purpose of the Study:

  • To evaluate how center effects are managed during randomization and statistical analysis in recent multicenter RCTs.
  • To determine the frequency and outcomes of subgroup analyses conducted by center in these trials.

Main Methods:

  • Methodological review of primary reports from multicenter RCTs published in 2024 in five major general medical journals.
  • Searched MEDLINE via PubMed for relevant studies.
  • Data extraction performed in duplicate.

Main Results:

  • Out of 188 included multicenter RCTs, 49% used center stratification/minimization in randomization, more common in non-pharmacological trials (75%) than pharmacological (27%).
  • Only 20% reported accounting for center in primary statistical analysis, and 36% accounted for center effect post-stratification/minimization.
  • Center subgroup analysis was reported in 10% of trials, with one showing a significant interaction.

Conclusions:

  • A minority of recent multicenter RCTs effectively account for center effects in their design and analysis.
  • The infrequent use of center stratification/minimization and statistical adjustment for center effects may limit the generalizability of findings.
  • Subgroup analyses by center are seldom conducted, hindering deeper understanding of site-specific variations.