Hyperkalemia After Initiating Renin–Angiotensin System Blockade: The Stockholm Creatinine Measurements (SCREAM) Project

BACKGROUND: Concerns about hyperkalemia limit the use of angiotensin‐converting enzyme inhibitors (ACE‐I) and angiotensin receptor blockers (ARBs), but guidelines conflict regarding potassium‐monitoring protocols. We quantified hyperkalemia monitoring and risks after ACE‐I/ARB initiation and developed and validated a hyperkalemia susceptibility score. METHODS AND RESULTS: We evaluated 69 426 new users of ACE‐I/ARB therapy in the Stockholm Creatinine Measurements (SCREAM) project with medication initiation from January 1, 2007 to December 31, 2010, and follow‐up for 1 year thereafter. Three fourths (76%) of SCREAM patients had potassium checked within the first year. Potassium >5 and >5.5 mmol/L occurred in 5.6% and 1.7%, respectively. As a comparison, we propensity‐matched new ACE‐I/ARB users to 20 186 new β‐blocker users in SCREAM: 64% had potassium checked. The occurrence of elevated potassium levels was similar between new β‐blocker and ACE‐I/ARB users without kidney disease; only at estimated glomerular filtration rate <60 mL/min per 1.73 m(2) were risks higher among ACE‐I/ARB users. We developed a hyperkalemia susceptibility score that incorporated estimated glomerular filtration rate, baseline potassium level, sex, diabetes mellitus, heart failure, and the concomitant use of potassium‐sparing diuretics in new ACE‐I/ARB users; this score accurately predicted 1‐year hyperkalemia risk in the SCREAM cohort (area under the curve, 0.845, 95% CI: 0.840–0.869) and in a validation cohort from the US‐based Geisinger Health System (N=19 524; area under the curve, 0.818, 95% CI: 0.794–0.841), with good calibration. CONCLUSIONS: Hyperkalemia within the first year of ACE‐I/ARB therapy was relatively uncommon among people with estimated glomerular filtration rate >60 mL/min per 1.73 m(2), but rates were much higher with lower estimated glomerular filtration rate. Use of the hyperkalemia susceptibility score may help guide laboratory monitoring and prescribing strategies.