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Research Guides@Tufts

Study Designs in the Health Sciences

An introduction to the main features and uses of study designs popular and unique to medicine and the health sciences.

Clinical Trials

What is a clinical trial?

“[A] clinical trial is any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcomes. Clinical trials may also be referred to as interventional trials. Interventions include but are not restricted to drugs, cells and other biological products, surgical procedures, radiologic procedures, devices, behavioural treatments, process-of-care changes, preventive care, etc. This definition includes Phase I to Phase IV trials.”[1] 

Trial Phases [1]:

I.  Clinical trials test a new biomedical intervention in a small group of people (e.g., 20-80) for the first time to evaluate safety (e.g., to determine a safe dosage range and to identify side effects).

II. Clinical trials study the biomedical or behavioral intervention in a larger group of people (several hundred) to determine efficacy and to further evaluate its safety.

III. Studies investigate the efficacy of the biomedical or behavioral intervention in large groups of human subjects (from several hundred to several thousand) by comparing the intervention to other standard or experimental interventions as well as to monitor adverse effects, and to collect information that will allow the intervention to be used safely.

IV. Studies are conducted after the intervention has been marketed. These studies are designed to monitor effectiveness of the approved intervention in the general population and to collect information about any adverse effects associated with widespread use.

Why use this study type?

  • Evaluating one or more interventions (for example, drugs, medical devices, approaches to surgery or radiation therapy) for treating a disease, syndrome, or condition. [2]
  • Finding ways to prevent the initial development or recurrence of a disease or condition. These can include medicines, vaccines, or lifestyle changes, among other approaches. [2]
  • Evaluating one or more interventions aimed at identifying or diagnosing a particular disease or condition.[2]
  • Examining methods for identifying a condition or risk factors for that condition.[2]
  • Exploring and measuring ways to improve the comfort and quality of life of people with a chronic illness through supportive care.[2]

Format and features

References

  1. World Health Organization (WHO). WHO International Clinical Trials Registry Platform Glossary. 2024. https://www.who.int/clinical-trials-registry-platform/about/glossary. Accessed November 6, 2024.
  2. ClinicalTrials.gov. Learn About Studies. 2024. https://clinicaltrials.gov/study-basics/learn-about-studies. Accessed November 6, 2024.
  3. University of California San Francisco. Clinical trial Protocol Development.2022. https://hub.ucsf.edu/protocol-development.Accessed November 6, 2024.
  4.  Centers for Disease Control and Prevention (CDC).TREND Statement Checklist. 2018. https://www.cdc.gov/trendstatement/pdf/trendstatement_TREND_Checklist.pdf. Accessed November 6, 2024.
  5. Equator Network. CONSORT 2010 Statement: updated guidelines for reporting parallel group randomised trials. 2024. https://www.equator-network.org/reporting-guidelines/consort/. Accessed November 6, 2024.

Example

Dose vitamin D supplementations improve peripheral diabetic neuropathy? A before-after clinical trial.

Ghadiri-Anari A, Mozafari Z, Gholami S, Khodaei SA, Aboutorabi-Zarchi M, Sepehri F, Nadjarzade A, Rahmanian M, Namiranian N.

Diabetes Metab Syndr. 2019 Jan-Feb;13(1):890-893. doi: 10.1016/j.dsx.2018.12.014.

Objective: Peripheral neuropathy is a common complication of diabetes mellitus. This study was set to assess the effect of vitamin D supplementation on peripheral neuropathy in patients with type 2 diabetes (T2DM).

Materials and methods: This study was a quasi-experimental trial in Yazd diabetic research center. Sixty T2DM subjects (30-65 years old) with painful diabetic neuropathy enrolled in this study from March 2017 till April 2018. Patients received weekly 50000 IU of vitamin D3 for 12 weeks orally. Evaluation of diabetic neuropathy was performed by using Michigan Neuropathy Screening Instrument (MNSI) before and after trial. Also fasting plasma glucose, HbA1c, calcium and vitamin D checked before and after the trial. SPSS version 20 software was used for statistical analysis. P ≤ 0.05 was considered to be statistically significant.

Results: Among 60 T2DM patients, 58 completed the study. Most of them (53.4%) were male. At the end of study, HbA1c, vitamin D, MNSI (both questionnaire and physical examination) improved that is statistically significant (p-value: <0.001).

Conclusion: Oral supplementation of vitamin D 3 (50,000 IU) once weekly for 12 weeks was associated with improvement in the serum level of vitamin D and significant decrease in the symptoms and sign of diabetic neuropathy. So serum vitamin D level should be checked in persons with diabetic neuropathy and low levels of it should be corrected in order to reducing neuropathy severity.