What are the guidelines for designing a prospective study?

Guidelines for Designing a Prospective Study

A prospective inception cohort study is the most favorable design for clinical research, providing the strongest evidence for evaluating outcomes over time. 1

Prospective studies require careful planning and systematic implementation to ensure valid, reliable, and reproducible results. The following guidelines outline the essential components for designing a high-quality prospective study:

Research Question and Objectives

• Clearly define your research question using the PICO format (Population, Intervention/Exposure, Comparator, Outcome) to structure and narrow the focus from a broad topic 2, 3
• Ensure your research question meets FINER criteria (Feasible, Interesting, Novel, Ethical, and Relevant) to generate new knowledge with clinical impact 2
• Specify the study objective(s) and classify the type of research as descriptive and/or analytical (explanatory or predictive) 1
• Identify gaps in current evidence and explain why a prospective study is the appropriate approach to address these gaps 1
• Limit to one primary objective while secondary objectives should typically not exceed five 3

Study Design Elements

• Clearly identify and describe the study design used to address the research question 1
• Document whether data are exclusively cross-sectional or include longitudinal components 1
• Specify the pre-planned sample size requirements and power calculations for the study 1
• Detail the eligibility criteria for participant selection, with particular attention to inclusion and exclusion criteria 1
• Consider stratification for relevant comorbidities or other important variables that may affect outcomes 1
• Distinguish between outpatient and inpatient populations if applicable 1

Participant Recruitment and Data Collection

• Document recruitment strategies to understand potential biases in the target sample 1
• Enroll consecutive patients beginning at study onset to avoid selection bias 1
• Systematically collect all symptoms and relevant data before diagnosis is established 1
• Provide details on methods of raw data collection, updates, completeness, data extraction, cleaning, and quality controls 1
• Specify the time points of core variables in relation to the disease trajectory 1
• Avoid undefined sampling (convenience sampling) and overlapping populations with other publications 1

Variables and Measurements

• Provide a complete list of core variables included in the study, grouped as baseline characteristics, exposures, and outcomes 1
• Identify the data source of each core variable, its definition, and describe how any derived variables were calculated and validated 1
• Describe variables in detail, including timing of collection and methods of assessment 1
• For studies involving biomarkers, provide details on description, timing, methods of assessment, and analytical validation 1
• Standardize laboratory confirmation methods and specify cutoff values for abnormal results 1

Statistical Analysis Plan

• Summarize the main aspects of the statistical analysis plan 1
• Specify pre-planned strategies to identify and mitigate the main sources of bias 1
• Clearly distinguish between prespecified and post hoc analyses, especially for subgroup analyses 1
• Provide information on planned assessments of internal and external validity 1
• Detail any planned sensitivity analyses 1

Ethical Considerations and Reporting

• Ensure the study protocol addresses ethical considerations and has appropriate approval 1
• Register the study protocol in an appropriate registry before beginning data collection 1
• Consider patient and public involvement and engagement (PPIE) in study design, conduct, and reporting 1
• Adhere to reporting guidelines such as ARRIVE Essential 10 for animal research or BePRECISE for precision medicine research 1
• Plan for complete and transparent reporting of all methods and results, including provision of data in supplementary materials when possible 1

Common Pitfalls to Avoid

• Avoid convenience selection of literature to support study rationale; prioritize the highest level of evidence 1
• Prevent overlap of the same population with other publications by coordinating efforts between departments 1
• Avoid unspecified exclusion criteria that vary between studies, leading to inconsistent populations 1
• Don't rely solely on a single data source when multiple sources could provide more comprehensive information 1
• Beware of insufficient sample size, which increases the risk for chance results 4

By following these guidelines, researchers can design prospective studies that produce valid, reliable results with meaningful clinical implications and minimize the risk of methodological flaws that could compromise the value of their research.