Consistency of Laboratory Monitoring During Initiation of Mineralocorticoid Receptor Antagonist Therapy in Patients With Heart Failure

Mineralocorticoid receptor antagonists (MRAs) are a cornerstone of heart failure therapy but have a risk of hyperkalemia.Clinical guidelines recommend close monitoring of renal function and electrolyte levels throughout the course of therapy. 1 No large studies have examined whether laboratory monitoring occurs routinely in community practice.Methods | Using the Centers for Medicare we identified incident MRA use by the presence of a Part D claim for eplerenone or spironolactone between May 1 and September 30, 2011, with no such claims between January 1 and April 30, 2011. 2 Outcomes included measurement of serum creatinine and potassium levels before and after MRA initiation, as suggested in guidelines.We defined appropriate testing as a claim for a specific test or laboratory panel including creatinine and potassium within 120 days before initiation, 2 or more measurements during the early postinitiation period (days 1 through 10), and 3 or more measurements during the extended postinitiation period (days 11 through 90).We counted each hospitalization as 1 test during that period.If the initial MRA prescription fill occurred within 3 days after discharge, we considered the patient to have both in-hospital initiation and 1 test during early postinitiation follow-up.We summarized laboratory testing using frequencies with percentages.We used multivariable logistic regression to estimate associations between patient characteristics and laboratory monitoring, adjusting for demographic characteristics and comorbid conditions.We used a 2-sided P < .05 to establish statistical significance and report 95% confidence intervals.We used SAS version 9.3 (SAS Institute Inc) for all analyses.