Few Disparities in Baseline Laboratory Testing After the Diuretic or Digoxin Initiation by Medicare Fee-For-Service Beneficiaries

BACKGROUND: Despite the persistence of significant disparities, few evaluations examine disparities in laboratory testing by race/ethnicity, age, sex, Medicaid eligibility, and number of chronic conditions for Medicare fee-for-service beneficiaries' newly prescribed medications. In Medicare beneficiaries initiating diuretics or digoxin, this study examined disparities in guideline-appropriate baseline laboratory testing and abnormal laboratory values. METHODS AND RESULTS: To evaluate guideline-concordant testing for serum creatinine and serum potassium within 180 days before or 14 days after the index prescription fill date, we constructed retrospective cohorts from 10 states of 99 711 beneficiaries who had heart failure or hypertension initiating diuretic in 2011 and 8683 beneficiaries who had heart failure or atrial fibrillation initiating digoxin. Beneficiaries initiating diuretics were less likely to have testing if they were non-Hispanic Black (relative risk [RR], 0.99; 95% confidence interval [CI], 0.98-0.99) than non-Hispanic White. Beneficiaries initiating diuretics and beneficiaries initiating digoxin were more likely to have testing if they had multiple chronic conditions relative to 0 to 1 conditions. Beneficiaries initiating diuretics with laboratory values were more likely to have an abnormal serum creatinine value at baseline if they were non-Hispanic Black (RR, 2.57; 95% CI, 1.91-3.44), other race (RR, 2.11; 95% CI, 1.08-4.10), or male (RR, 2.75; 95% CI, 2.14-3.52) or an abnormal serum potassium value if they were aged ≥76 years (RR, 1.29; 95% CI, 1.09-1.51) or male (RR, 1.17; 95% CI, 1.03-1.33). CONCLUSIONS: Testing rates were consistently high, so there were negligible disparities in guideline-concordant testing of creatinine and potassium after the initiation of digoxin or diuretics by Medicare beneficiaries.