Baseline laboratory monitoring of cardiovascular medications in elderly health maintenance organization enrollees.

OBJECTIVES: To identify correlates of laboratory monitoring errors in elderly health maintenance organization (HMO) members at the initiation of therapy with cardiovascular medications.
DESIGN: Cross-sectional study in 10 HMOs.
SETTING: United States. PARTICIPANTS: From a 2 million-member sample, individuals aged 65 and older who received one of seven cardiovascular medications (angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), amiodarone, digoxin, diuretics, potassium supplements, and statins) and did not have recommended baseline monitoring performed during the 180 days before or 14 days after the index dispensing. MEASUREMENTS: The proportion of members receiving each drug for whom recommended laboratory monitoring was not performed. Laboratory monitoring error rates stratified by sex, age group, chronic disease score, and HMO site were examined, and logistic regression was used to identify predictors of laboratory monitoring errors.
RESULTS: Error rates varied by medication class, ranging from 23% of patients receiving potassium supplementation without serum potassium and serum creatinine monitoring to 58% of patients receiving amiodarone who did not have recommended monitoring for thyroid and liver function. Highest error rates occurred in the youngest elderly for ACE inhibitors, ARBs, digoxin, diuretics, and potassium supplements, although in patients receiving amiodarone and statins, errors were most frequent in the oldest elderly. Errors occurred more frequently in patients with less comorbidity.
CONCLUSION: Laboratory monitoring errors occurred frequently in elderly HMO members at the initiation of therapy with cardiovascular medications. Further study must examine the association between these errors and adverse outcomes.