A real-world cohort study on the quality of potassium and creatinine monitoring during initiation of mineralocorticoid receptor antagonists in patients with heart failure.

Aims: Clinical heart failure (HF) guidelines recommend monitoring of creatinine and potassium throughout the initial weeks of mineralocorticoid receptor antagonists (MRAs) therapy. We here assessed the extent to which this occurs in our health care. Methods and results: Observational study in 2007-2010 HF patients starting MRA therapy in Stockholm, Sweden. Outcomes included potassium and creatinine laboratory testing before MRA initiation and in the early (Days 1-10) and extended (Days 11-90) post-initiation periods. Exclusion criteria considered death/hospitalization within 90 days, and lack of a second MRA dispense. Of 4036 HF patients starting on MRA, 45% were initiated from a hospital, 24% from a primary care centre, and 30% from other private centres. Overall, 89% underwent pre-initiation testing, being more common among hospital (97%) than for primary care (74%) initiations. Only 24% were adequately monitored in all three recommended intervals, being again more frequent following hospital (33%) than private (21%) or primary care (17%) initiations. In multivariable analyses, adequate monitoring was more likely for hospital [odds ratio (OR) 2.85, 95% confidence interval (95% CI) 2.34-3.56] initiations, and for patients with chronic kidney disease (OR 1.79, 95% CI 1.30-2.43) and concomitant use of angiotensin-converting enzyme (OR 1.27, 95% CI 1.05-1.52), angiotensin receptor blockers (OR 1.19, 95% CI 1.01-1.40) or beta-blockers (OR 1.65, 95% CI 1.22-2.26). Age, sex, and prescribing centre explained a small portion of adequate monitoring (c-statistic 0.63). Addition of comorbidities and medications improved prediction marginally (c-statistic 0.65). Conclusion: Although serum potassium and creatinine monitoring before MRA initiation for HF is frequent, rates of post-initiation monitoring remain suboptimal, especially among primary care centres.