Clinical Trials Methodology

The goal of a clinical study is to determine whether a new drug, treatment, or device is safe for human use or consumption. Clinical research can provide insights into the areas, including disease diagnosis, cause, care, and cure. Clinical trials are an important part of the clinical research process to evaluate the effectiveness and safety of medications or medical devices. They are generally developed along with the four-phase trials. Scientifically appropriate research methodology plays a vital role within biomedicine. Following the best medical practices contribute to avoidable morbidity and mortality. The research methods must be continually revised and updated as better methods become available.

Randomized Trials

The randomized trial is the cornerstone of evidence-based medicine and there is growing emphasis on evidence-based medicine and incorporation of high-quality evidence into clinical practice. In randomized trials, people are randomly allocated to receive or not receive any intervention/treatment. By the control group, researchers can determine the effect of the intervention and assess whether the results were accidental or the effect of the intervention. Randomized trials are the gold standard for clinical study and many therapies have historically been evaluated.

Randomization procedures. Fig.1 Randomization procedures. (Kao, 2008)

Systematic Reviews

There are other types of clinical studies such as systematic reviews that is critical assessment and evaluation of existing research. It attempts to address the clinical problems using an approach designed to reduce the likelihood of overall outcome bias. In addition, systematic reviews can help understand the interventions that are already known. The treatments or interventions will need further study if there is a gap in our understanding, or if the treatment effect is poor. Systematic review protocols should include details such as project objectives, detailed methods, and processes, study eligibility criteria, data extraction, and analyses.

Retrospective Studies

Retrospective studies are defined as using available data on current and past patients to answer questions. These studies are carried out by assembling and organizing information about past events. Further information about the past can be obtained by analyzing previously stored biological samples. In retrospective studies, the potential confounding factors are unavailable for analysis because they are not included in clinical records. Besides, the quality of records is often poor in retrospective studies and the reason is that most recording systems were designed for clinical purposes rather than research.

Prospective Studies

Prospective studies typically use new data from current and future patients over a future period to answer questions. In the sense of manipulating study-related treatments, prospective studies may be either non-interventional or interventional. Prospective studies have the advantage over retrospective studies in that they allow investigators to plan and manage data collection, and answer specific research questions more directly. However, reverse causation error may also occur in prospective studies of long-term exposures and/or chronic disease. Generally, clinical research errors are best avoided through robust study design and thoughtful statistical analysis.

Clinical trials are prospective. Fig.2 Clinical trials are prospective. (Levin, 2006)


  1. Kao, L., Tyson, J., Blakely, M. and Lally, K., 2008. Clinical Research Methodology I: Introduction to Randomized Trials. Journal of the American College of Surgeons, 206(2), pp.361-369.
  2. Levin, K., 2006. Study design III: Cross-sectional studies. Evidence-Based Dentistry, 7(1), pp.24-25.
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