There are 4 main steps to consider for the design of a QoL study:
- Determine your QOL Objective
- Write down the specific question you want to answer. Take extra care to determine which specific QoL domains, what time periods and what type of changes/differences you are expecting to be relevant for your question.
- Choose an instrument
- It should be a validated (i.e. reliable, valid, responsive, feasible ?) questionnaire in the trial population.
- It should address the QoL domains that are essential for your hypothesis: global measures, disease-specific measures,and symptom checklists.
- Check if appropriate translations are available.
- Select your assessment time points
- Assessment schedule should closely reflect the objective.
- Schedule should include at least a baseline (i.e. before treatment/randomization).
- If comparing multiple arms: schedule should be identical/comparable between the arms.
- Keep the patient in mind: do not overburden by collecting more than necessary.
- Develop an analysis plan
- Analysis plan should reflect the objective.
- Address issues of scale/domain selection, sample size, compliance, missing data, minimal clinically important difference and sensitivity analyses.
Note that objectives, instrument, assessment schedule and analysis techniques should be specified a priori. A good trial design, conduct, analysis and reporting is only possible if these aspects have been determined beforehand.