02. Build an evidence-gap and feasibility brief
Lesson
LEARNING OBJECTIVES
Create a traceable preliminary evidence map, distinguish an absent finding from an absent study, and identify a feasible contribution before committing to a design.
SEARCH TO REFINE THE QUESTION
Start with a few main concepts and their synonyms. Combine synonyms with OR and concepts with AND, adapting syntax to each database. Test whether your strategy retrieves relevant papers you already know. Excessive location, language, outcome or date restrictions can exclude useful evidence; justify restrictions rather than applying them automatically.
Record the database, search date, full strategy and filters. For each useful report, record the citation, population, design, outcome definition, main result, limitation and relevance to your proposed question. Link multiple publications from the same study so they are not mistaken for independent evidence.
A preliminary evidence map is not automatically a systematic review. Use it to identify whether the uncertainty concerns frequency, an exposure relationship, implementation, measurement or context. Then decide what a new study would add.
WORKED FICTIONAL EVIDENCE MAP
For missed appointments, imagine three records: a register analysis using appointment-level attendance, an interview study describing transport barriers, and a reminder trial in another setting. The first describes recorded attendance, the second explores experiences, and the third estimates an intervention effect under its own conditions.
Do not average their results or conclude that the trial will transfer unchanged. Compare definitions, eligibility, setting, resources and the proposed mechanism. The local gap might concern current register completeness or implementation barriers rather than a need to repeat the same trial immediately.
CHECK FEASIBILITY EARLY
Ask who controls the data, whether access is authorized, which groups are missing, whether exposure and outcome timing can be reconstructed, what measurements need piloting, and which methodological and language skills are available. Write down time, staffing, cost and review requirements. Distinguish confirmed resources from assumptions.
YOUR TASK
Find and read three accessible sources relevant to your question. Build a small evidence table and a search log. Write a 150-word gap statement: what is known, what remains uncertain, why the uncertainty matters and how your proposed study could help.
Add three feasibility risks, an owner for each, a next action and a decision date. Define a stopping or redesign criterion, such as failure to obtain a credible sampling frame.
SELF-CHECK
Does a missing outcome in an abstract mean the study never measured it? Is finding only two papers evidence that none other exist?
FEEDBACK
No. Inspect the full report, supplementary material or linked reports where permitted, and record “unclear” when necessary. Limited retrieval may reflect the search strategy or access. Avoid overstating the evidence gap.
PORTFOLIO OUTPUT
A dated search log, evidence map, justified gap statement and feasibility register.
FURTHER READING
Cochrane Handbook, Chapter 4: Searching for and selecting studies.
https://training.cochrane.org/handbook/current/chapter-04
Chapter 5: Collecting data from studies.
https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-05
Create a traceable preliminary evidence map, distinguish an absent finding from an absent study, and identify a feasible contribution before committing to a design.
SEARCH TO REFINE THE QUESTION
Start with a few main concepts and their synonyms. Combine synonyms with OR and concepts with AND, adapting syntax to each database. Test whether your strategy retrieves relevant papers you already know. Excessive location, language, outcome or date restrictions can exclude useful evidence; justify restrictions rather than applying them automatically.
Record the database, search date, full strategy and filters. For each useful report, record the citation, population, design, outcome definition, main result, limitation and relevance to your proposed question. Link multiple publications from the same study so they are not mistaken for independent evidence.
A preliminary evidence map is not automatically a systematic review. Use it to identify whether the uncertainty concerns frequency, an exposure relationship, implementation, measurement or context. Then decide what a new study would add.
WORKED FICTIONAL EVIDENCE MAP
For missed appointments, imagine three records: a register analysis using appointment-level attendance, an interview study describing transport barriers, and a reminder trial in another setting. The first describes recorded attendance, the second explores experiences, and the third estimates an intervention effect under its own conditions.
Do not average their results or conclude that the trial will transfer unchanged. Compare definitions, eligibility, setting, resources and the proposed mechanism. The local gap might concern current register completeness or implementation barriers rather than a need to repeat the same trial immediately.
CHECK FEASIBILITY EARLY
Ask who controls the data, whether access is authorized, which groups are missing, whether exposure and outcome timing can be reconstructed, what measurements need piloting, and which methodological and language skills are available. Write down time, staffing, cost and review requirements. Distinguish confirmed resources from assumptions.
YOUR TASK
Find and read three accessible sources relevant to your question. Build a small evidence table and a search log. Write a 150-word gap statement: what is known, what remains uncertain, why the uncertainty matters and how your proposed study could help.
Add three feasibility risks, an owner for each, a next action and a decision date. Define a stopping or redesign criterion, such as failure to obtain a credible sampling frame.
SELF-CHECK
Does a missing outcome in an abstract mean the study never measured it? Is finding only two papers evidence that none other exist?
FEEDBACK
No. Inspect the full report, supplementary material or linked reports where permitted, and record “unclear” when necessary. Limited retrieval may reflect the search strategy or access. Avoid overstating the evidence gap.
PORTFOLIO OUTPUT
A dated search log, evidence map, justified gap statement and feasibility register.
FURTHER READING
Cochrane Handbook, Chapter 4: Searching for and selecting studies.
https://training.cochrane.org/handbook/current/chapter-04
Chapter 5: Collecting data from studies.
https://www.cochrane.org/authors/handbooks-and-manuals/handbook/current/chapter-05
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