Related Experiment Video

Updated: Jul 27, 2026

A Clinical Trial Assessing the Safety, Efficacy, and Delivery of Olive-Oil-Based Three-Chamber Bags for Parenteral Nutrition
04:53

A Clinical Trial Assessing the Safety, Efficacy, and Delivery of Olive-Oil-Based Three-Chamber Bags for Parenteral Nutrition

Published on: September 20, 2019

Patterns of patient enrollment in randomized controlled trials

A B Haidich1, J P Ioannidis

  • 1Clinical Trials and Evidence-Based Medicine Unit, Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece.

Journal of Clinical Epidemiology
|August 25, 2001
PubMed

Insights

Early enrollment in randomized controlled trials (RCTs) strongly predicts if trials will meet their enrollment targets. This finding is crucial for assessing trial feasibility and future recruitment success.

Area of Science:

  • Clinical Trials
  • Epidemiology
  • Health Services Research

Background:

  • Recruitment challenges are common in clinical trials.
  • Predicting trial success early is vital for resource allocation.
  • Understanding enrollment patterns can optimize trial design.

Purpose of the Study:

  • To describe enrollment patterns in a large cohort of AIDS Clinical Trials Group (ACTG) randomized controlled trials (RCTs).
  • To evaluate if early recruitment predicts the ability of RCTs to reach their target enrollment.
  • To identify factors influencing RCT enrollment.

Main Methods:

  • Analysis of 77 efficacy RCTs initiated by the ACTG between 1986 and 1996.
  • Inclusion of 28,992 patients enrolled until November 1999.
  • Examination of enrollment trajectories and correlation with target attainment.

Main Results:

  • 17% of RCTs failed to reach half their target recruitment.
  • Initial accrual rates significantly determined subsequent enrollment rates (P < 0.001).
  • Early enrollment (first 1-3 months) strongly correlated with overall trial accrual (P < 0.001).

Conclusions:

  • Early enrollment is a strong indicator of a trial's feasibility and future recruitment pace.
  • Factors such as patient pool, eligibility criteria, trial attractiveness, and site adequacy influence enrollment.
  • Understanding early enrollment dynamics can improve the success rate of clinical trials.

More Related Videos

E-Patient Counseling Trial (E-PACO): Computer Based Education versus Nurse Counseling for Patients to Prepare for Colonoscopy06:28

E-Patient Counseling Trial (E-PACO): Computer Based Education versus Nurse Counseling for Patients to Prepare for Colonoscopy

Published on: August 1, 2019

A Video Protocol of a Randomized Controlled Clinical Trial - Electrochemotherapy of Cutaneous Metastases with Reduced Dose Bleomycin (BLESS Trial)04:11

A Video Protocol of a Randomized Controlled Clinical Trial - Electrochemotherapy of Cutaneous Metastases with Reduced Dose Bleomycin (BLESS Trial)

Published on: June 9, 2026

Related Concept Videos

Randomized Experiments01:13

Randomized Experiments

The randomization process involves assigning study participants randomly to experimental or control groups based on their probability of being equally assigned. Randomization is meant to eliminate selection bias and balance known and unknown confounding factors so that the control group is similar to the treatment group as much as possible. A computer program and a random number generator can be used to assign participants to groups in a way that minimizes bias.
Simple randomization
Simple...
Clinical Trials01:16

Clinical Trials

Clinical trials are prospective experimental studies conducted on humans to determine the safety and efficacy of treatments, drugs, diet methods, and medical devices. Using statistics in clinical trials enables researchers to derive reasonable and accurate conclusions from the collected data, allowing them to make wise decisions in uncertain situations. In medical research, statistical methods are crucial for preventing errors and bias.
There are four phases in a clinical trial. A phase one...
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.
Clinical Trials: Overview01:11

Clinical Trials: Overview

Clinical development focuses on how the drug will interact with the human body and encompasses four key phases of clinical trials, each serving a specific purpose in assessing the safety and effectiveness of new drugs. These phases overlap and build upon one another. Phase I involves a small group of healthy volunteers (typically 20-80 individuals) or, in cases where significant toxicity is expected, patients with the targeted disease, such as cancer or AIDS. The volunteers are tested for...
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...
Bioavailability Study Design: Healthy Subjects Versus Patients01:15

Bioavailability Study Design: Healthy Subjects Versus Patients

Bioavailability studies are essential for evaluating a drug's therapeutic efficacy and understanding its absorption patterns under various physiological conditions. Conducting such studies on target patient populations provides more relevant data by simulating real-world disease states. However, practical challenges often necessitate the use of young, healthy adult volunteers as study subjects.Patients may exhibit altered drug absorption patterns due to the effects of the disease itself,...