What do you think is meaningful and likely to change via your intervention in the proposed time frame?
Find out if there are any outcomes recommended by expert panels for inclusion in clinical trials in your population. For example, for osteoarthritis, there is a 1996 paper entitled, "Design and conduct of clinical trials in patients with osteoarthritis: recommendations from a task force of the Osteoarthritis Research Society. Results from a workshop." This spells out study design issues and recommends a core set of outcomes to include in clinical trials in those with osteoarthritis.
Keywords to try when searching PubMed and other databases for similar papers in your population: expert panel, task force, work group, working group OR the name of the research group for your population if known (e.g., OARSI)..
Are there accepted/expected measures you need to include?
What measures will allow you to draw comparisons to existing studies?
For the specific measure:
• Are there validation studies in your population?
• Multiple versions (number of items, scale format [Likert, NRS])?
• Are there MCID, MCII, PASS, norms available to give meaning?
• Minimal Clinically Important Difference (MCID)
• Minimal Clinically Important Improvement (MCII)
• Patient Acceptable Symptom State (PASS)
• Population norms (also check scoring manual)
Read the actual questions to see if the instrument captures what you want
Also check whether any grouping of questions into subscales make sense
Be aware if there are multiple versions (e.g., 36-item vs. 12-item versions; 60-seconds vs. 90-seconds)
Also find the scoring manual/instructions in advance
Instrument is useless if you can't score it
Finding the questionnaire/inventory/index/scale
Title words in studies which often have the instrument questions listed (development, psychometric, reliability, validity, validation