Selecting the appropriate study design is crucial for the effective execution of clinical research. Researchers can choose from a variety of study designs within two main categories: observational and interventional studies. Each design offers unique strengths and weaknesses, and understanding these limitations is essential for drawing accurate conclusions.
Observational study designs, also called epidemiological study designs, are often retrospective and are used to assess potential causation in exposure-outcome relationships. Observational study designs include ecological designs, cross sectional, case-control, case-crossover, retrospective and prospective cohorts. Interventional studies are prospective and are specifically tailored to evaluate direct impacts of treatment. Each design has specific outcome measures that depend on the type and quality of data used. Addressing the potential limitations of each study design during the planning phase is critical.
There are numerous published guidelines and standards for the design, execution, and reporting of clinical research that help in selecting the most appropriate study design and ensuring the quality of research. These guidelines cover various categories of study designs, including observational studies (e.g., STROBE, Strengthening the Reporting of Observational Studies in Epidemiology), Interventional Studies (e.g., CONSORT, Consolidated Standards of Reporting Trials), Systematic Reviews and Meta-Analyses (e.g., PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The purpose of these standards and guidelines is to structure and enhance the quality of clinical research design, execution, and reporting.
Let’s have a look of some of the key guidelines available:
- Strengthening the Reporting of Observational studies in Epidemiology (STROBE) is a collection of guidelines specifically for standardization and improvement of the reporting of observational epidemiological research. There are specific subcategories of the STROBE standards including molecular epidemiology (STROBE-ME), infectious diseases (STROBE-ID) and genetic association studies (STREGA) – www.strobe-statement.org.
- Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) is a 27-item checklist and multiphase flow diagram to improve quality of reporting systematic reviews and meta-analyses. It replaces the QUOROM statement – www.prisma-statement.org.
- Consolidated Standards Of Reporting Trials (CONSORT) are interventional study standards and consists of a 25 item checklist and flowchart designed for randomized clinical trials (RCTs) to standardize reporting of key elements including design, analysis and interpretation of the RCT – www.consort-statement.org.
- Consolidated criteria for reporting qualitative research (COREQ) is a 32-item checklist intended for reporting of qualitative data from interviews and focus groups – https://www.equator-network.org/reporting-guidelines/coreq/.
- Statistical Analyses and Methods in the Published Literature (SAMPL) is a guideline for statistical methods and analyses of all types of clinical research – https://www.equator-network.org/wp-content/uploads/2013/03/SAMPL-Guidelines-3-13-13.pdf
- Standards for Reporting Studies of Diagnostic Accuracy (STARD) is a 25-item checklist and flow diagram designed for the reporting of diagnostic studies – www.stard-statement.org
- Quality assessment of diagnostic accuracy studies (QUADAS) is a quality assessment of diagnostic accuracy studies – www.bris.ac.uk/quadas
- Consensus-based Clinical Case Reporting Guideline Development (CARE) is a checklist comprised of 13-item and is designed only for case reports – www.carestatement.org
- Standards for Quality Improvement Reporting Excellence (SQUIRE) are guidelines including 19 elements, for authors aimed at quality improvement in health care reporting – www.squire-statement.org
- Consolidated Health Economic Evaluation Reporting Standards (CHEERS) is a 28 element checklist of reporting practices for economic evaluations of interventional studies – https://www.equator-network.org/reporting-guidelines/cheers/
- Enhancing transparency in reporting the synthesis of qualitative research (ENTREQ) is a guideline specifically for standardizing and improving the reporting of qualitative biomedical research – https://www.equator-network.org/reporting-guidelines/entreq/
When designing or evaluating a study, it is beneficial to review the relevant standards before planning, executing, and/or publishing the study. All published standards and guidelines are accessible on their respective websites listed above. Additionally, the “Enhancing the Quality and Transparency of Health Research” (EQUATOR) network (www.equator-network.org) provides guidelines and checklists for the mentioned study designs and categories. This resource is continually updated with new standards to ensure high-quality and transparent research.