Parikh RV, Nash DM, Brimble KS, et al. - This study was intended to assess kidney function and potassium monitoring after the initiation of renin-angiotensin-aldosterone system blockade therapy and outcomes in 2 North American populations. Researchers performed 2 population-based retrospective cohort studies in Kaiser Permanente Northern California and Ontario, Canada. They matched individuals with outpatient serum creatinine and potassium tests in the 30 days after starting ACE inhibitor or angiotensin II receptor blocker therapy in a 1:1 ratio to patients without follow-up tests. The Cox regression was applied to assess the association of follow-up testing with 30-day all-cause mortality and hospitalization with acute kidney injury or hyperkalemia. After ACE inhibitor or angiotensin II receptor blocker initiation, routine laboratory monitoring was not associated with a lower risk of 30-day mortality. They distinguished patient subgroups in which targeted testing may be effective in distinguishing therapy-related variations in serum potassium or kidney function.