The study designing process is essential in clinical trials. A lot of consideration is needed on the type of study that is needed for your desirable outcomes.
Overview of the Process
The following method describes the process involved in determining the correct design type for your future clinical trial. This includes determining the appropriate research strategy, writing justification and protocol, calculating sample sizes, deciding on criteria for subject selection, and choosing the correct comparison groups. Strategically, the studies could be RCT or non-RCT: Cohort, Case-control, Cross-sectional, Observational, and Quasi-experimental. In this article, an overview will be provided on the listed study types. This will enable key innovators in coming to an inclusive decision on the appropriate study design for their desired study outcomes.
Table of Contents
What Study Design Should You Go For?
Randomised Controlled Trials (RCTs)
Randomised controlled trials (RCTs) are the gold standard in clinical research. Dating back to 1923, RCTs involve randomly assigning participants to two or more groups (an experimental group and a control group) and comparing the outcomes of the groups to determine the effectiveness of a treatment or intervention. Although the first idea of randomization was introduced in 1923, the first randomized control trial was carried out on streptomycin in 1946.
Atlantia Clinical Trials often performs this design type. One such study is 'A randomised, double-blind, parallel, placebo-controlled study to investigate the efficacy of Lactobacillus paracasei N1115 in gut development of young children’. In this study, infants and young children between the ages of 6 months and 3 years were administered a probiotic consisting of the LP N1115 strain (n=30) or a placebo supplement (n=30) over an 8-week intervention period.
Observational Studies
Observational studies observe and collect data on participants without intervening or manipulating any variables. These studies can be either prospective or retrospective. The 3 types of observational studies are:
Cohort Studies
Cohort studies follow a group of people (a cohort) over time to observe the development of a disease or condition. They can be either prospective or retrospective.
A 2020 prospective cohort study found an association between lower physical fitness and depression. The study observed that people with depression at baseline were more likely to experience depressive symptoms several years later if they had lower fitness levels compared to those with higher fitness.
Case-Control Studies
Case-control studies compare a group of people with a disease or condition (the cases) to a group of people without the disease or condition (the controls) to identify potential risk factors. These studies are relatively quick, economical, and easy to design and implement.
Cross-Sectional Studies
Cross-sectional studies involve collecting data on a group of people at a single point in time to determine the prevalence of a disease or condition or to explore relationships between variables.
Quasi-Experimental Studies
Quasi-experimental studies involve manipulating a variable but do not involve randomization of participants to different groups. This study type is useful in settings where randomization is not feasible or ethical, such as studying policies or environmental changes.
Choosing the Correct Comparison Group
Choosing the appropriate comparison group is also a strategic decision:
Parallel Clinical Trials
Participants are randomly assigned into two or more groups, each receiving a different treatment or intervention. The groups are then observed and compared over a specified period to determine each treatment's effectiveness and safety.
A randomised, double-blind, parallel, placebo-controlled study with treatment and placebo groups.
Cross-Over Clinical Trials
Participants receive multiple treatments or interventions in a predetermined sequence. Each participant serves as their control, receiving both treatments, and the effects are compared within the same individual. This design reduces the number of participants needed for a study.
A study designed as a randomised, double-blind, placebo-controlled, cross-over trial.
Key Takeaways
- Study Design Importance: Choosing the right study design is critical for achieving reliable and valid results in clinical trials.
- RCTs as Gold Standard: Randomised Controlled Trials are highly regarded for minimizing bias and establishing causality.
- Observational Studies: Useful for understanding associations and long-term outcomes without intervention.
- Quasi-Experimental Designs: Beneficial when randomization is not feasible, allowing for practical evaluation of interventions.
- Comparison Groups: Parallel and cross-over trials help in understanding the effectiveness of treatments by comparing different groups or treatments within the same group.
FAQs
How do I choose the right study design for my clinical trial?
The choice of study design depends on the specific research question, the type of intervention, the condition being studied, and ethical considerations. Randomised Controlled Trials (RCTs) are ideal for testing the efficacy of interventions, while observational studies are suitable for exploring associations and risk factors.
What is the difference between prospective and retrospective cohort studies?
Prospective cohort studies follow a group of individuals over time from the present into the future to observe outcomes, while retrospective cohort studies look back at existing data from a group of individuals to assess outcomes.
Why are RCTs considered the gold standard in clinical research?
RCTs are considered the gold standard because they use randomization to minimize bias, allowing for a clearer determination of causality between the intervention and the outcome.
What are the advantages of case-control studies?
Case-control studies are relatively quick, economical, and easy to design and implement. They are particularly useful for studying rare diseases or conditions.
When should I use a cross-over trial design?
Cross-over trials are useful when the treatments being studied are expected to have similar effects or when there is concern about individual variability in response to treatments. They also help reduce the number of participants needed for a study.
What challenges might I face during the validation stage of a clinical trial?
Common challenges include multiple rounds of requests for information, documents not in the right format, missing cited publications, and improperly redacted confidential data. Ensuring complete and correctly formatted documentation can help streamline the process.
How has the Covid-19 pandemic impacted clinical trial submissions?
The Covid-19 pandemic has led to fewer submissions due to restrictions on human studies and research. Both EFSA and applicants are still adapting to the new process, and as familiarity with the system grows, timelines may improve.
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