PHP91 Factors Affecting Serum Potassium Measurements After Initiation of Spironolactone at an Academic Medical Center

Abstract

Serum potassium levels should be assessed periodically following the initiation of spironolactone treatment. This study examined the rate of laboratory follow-up and factors affecting it at an academic medical center. Adult patients starting spironolactone treatment between January 1, 2008 and September 30, 2010 were studied. Subjects were excluded if the indicated disease was not followed up at the medical center, or the exact date of the first spironolactone prescription was unknown. Data were collected by computer query and chart review. Survival analysis examined the factors predicting the time to first serum potassium testing after spironolactone initiation. A total of 161 patients were included (mean age 51.1 years, 57% female), 29% of whom had some renal impairment (creatinine clearance <60 ml/min). Spironolactone was most commonly used for ascites/edema due to primary liver disease (45.3%), followed by congestive heart failure (19.3%) and polycystic ovary syndrome or other hormone-related disorders (18.6%). The median time to first potassium test was 22 days. After adjusting for age, gender, renal function and insurance status, medical indication was the only factor impacting time to first potassium check-up. Compared to patients with primary liver disease, patients who used spironolactone for ascites/edema not due to hepatic or cardiac causes (e.g., non-hepatic malignancy, nephrotic syndrome) were likely to have a potassium level checked earlier (hazard ratio [HR]=2.2, 95% CI=1.04-4.6), whereas potassium testing was more likely to be delayed in patients with hormone-related disorders (HR=0.4, 95% CI=0.2-0.9) or hypertension (HR=0.4, 95% CI=0.2-0.8). Medical indication was significantly predictive of the time to first potassium check in patients receiving spironolactone. It is surprising that renal dysfunction was not a factor, while the association with indication has many possible explanations from increased routine lab testing for some indications and higher risks of hyperkalemia complications. Further studies are needed to validate and understand these data.