1) Processing information into high levels of evidence takes time, and there is no guarantee that evidence exists at all levels for a specific clinical question.
2) Start with the highest level of evidence available. High-level resources build upon resources found in the lower levels of the pyramid to provide concise and up to date information.
3) Preappraised resources have a strict filtering process to insure that only high-quality information is included. Good resources will make their filtering processes readily available to users.