Related Experiment Video
Updated: Aug 23, 2026

Inverse Probability of Treatment Weighting (Propensity Score) using the Military Health System Data Repository and National Death Index
Published on: January 8, 2020
The reuse of subjects in clinical studies: is a bias introduced? Is there a threat to study validity?
1Department of Pulmonary/Critical Care Medicine and Harlem Lung Center, Columbia University, New York, New York 10037, USA. grp4@columbia.edu
Abstract:
The reuse of subjects in clinical studies to answer specific research questions is a common practice. This reuse can take many forms and is at least partly related to study efficiency. It is much easier to reuse known subjects who know the system(s) or are easy to find than to recruit new ones. A hypothetical question is: Are there instances when such practices may not be scientifically valid? This question will be addressed from the perspective of the case-control and experimental study design.
Related Concept Videos
Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
Bias in Epidemiological Studies
Bias
In statistics, a sampling bias is created when a sample is collected from a population, and some members of the population are not as likely to be chosen as others (remember, each member...
Blinding
Blind Procedures
Bioavailability Study Design: Healthy Subjects Versus Patients