It answers how the patent has improved or not improved. This is a very personal set of facts about a patient - did the person smoke - what age and sex are they,,,, and then - did the procedure help, or not - and to what extent.... This information can be useful for determining (along with data of other patients) how successful a path of treatment tends to be for similar patients. The information is used to determine if a person will likely benefit by looking at similar cases from this data.