Cohort Attrition Study Results: PRESERVE

- When using Step 0 as the starting step, the most severe reductions in patient retention appear to be at Steps 2 and 3, which apply serum creatinine related cohort requirements. These are more domain specific than the general visit requirements put in place in prior attrition steps, so this drop is expected. - Some separation between sites appears around Step 3, and using Step 2 as the starting step makes this appear even more stark. Step 3 introduces a requirement for the patient to be between the ages of 0-18 at the time of their creatinine measurement, and the pediatric institutions are more likely to have a large population of patients in this age range. - There is a drop in patients between Steps 7 and 8 (applying the first exclusion criteria), but subsequent exclusion steps do not seem to significantly reduce the overall size of the cohort.