PS1-06: Increased Incident Renal Disease with ACE-1 + Thiazide Therapy for Hypertension: The Geisinger Clinic Population
Clinical Medicine & Research
and Aims: Angiotensin converting enzyme (ACE) inhibitors are widely used in patients with chronic kidney disease (CKD) because the drugs slow disease progression. But some physicians are reluctant to prescribe ACE inhibitors "or use higher doses" because of concerns about the risk of hyperkalemia (high potassium), a potentially fatal adverse effect. Physicians need a tool to help them predict the risk of hyperkalemia; for example, high risk patients could be targeted for intensive laboratory
... nsive laboratory monitoring. We synthesized known predictors of hyperkalemia into a prognostic risk score to predict the risk of hyperkalemia. Methods: We assembled a retrospective cohort of adult patients with possible CKD (at least one recently estimated glomerular filtration rate (eGFR) value less than 60 mL/min/1.73m2) who started an ACE inhibitor between 1998 and 2006 at Kaiser Permanente Northwest, a health maintenance organization (HMO). We followed patients for the earliest evidence of hyperkalemia: (1) potassium value > 5.5 mmol/L; (2) diagnosis code for hyperkalemia (ICD-9-CM 276.7). Cox regression synthesized known predictors of hyperkalemia that were recorded in the electronic medical record or KPNW databases into a risk score to predict the absolute risk of hyperkalemia 90 days after starting therapy. Results: We followed 5,097 patients who experienced 145 hyperkalemic events, a 90 -day risk of 2.1% (95% CI 1.9% to 2.4%). The following baseline characteristics predicted hyperkalemia and contributed to the risk score: age, eGFR, diabetes, heart failure, current use of potassium supplements, current use of potassium sparing diuretics (e.g., spironolactone), and a high starting dose for the ACE inhibitor. The risk score discriminated high-risk patients (top quintile, observed risk of 7%) from low risk patients (bottom quintile, observed risk of 0.7%). Predicted and observed risks agreed closely (within 1%) for each quintile. Conclusions: The risk score separated high-risk patients (who may need more intensive laboratory monitoring) from low risk patients (whose physicians could use ACE-inhibitors more confidently). If validated in other clinical settings, the risk score could improve the efficiency of laboratory monitoring for hyperkalemia by focusing attention on higher risk patients.