Screening and eligibility: get it right before you launch, not after

Every research team has a story about a study that had to be re-run, or partially thrown out, because the eligibility requirements didn’t actually screen for what mattered. It’s an expensive mistake, and it’s almost always discovered too late to fix cheaply.

The fix is front-loading the work: writing eligibility requirements as precisely as the research questions themselves, before recruitment starts, not adjusting them reactively once responses start looking off.

A useful discipline is to write down, for each requirement, what specific risk it’s guarding against. If you can’t name the risk, the requirement is probably decorative -- either drop it, or you haven’t actually figured out what you need yet.

It’s also worth deciding upfront what "pending" and "under review" actually mean for your study, since ambiguous eligibility states are where studies quietly drift off track without anyone noticing until the data comes back strange.