Patient Safety and Quality

Doctors often fail to order laboratory monitoring when elderly HMO outpatients begin cardiovascular medications

Laboratory monitoring tests are often required when people begin taking a medication that has the potential to damage organs such as the liver or kidneys. Yet physicians often fail to order recommended laboratory monitoring tests in outpatient elderly HMO members who begin therapy with high-risk cardiovascular medications, concludes a study supported by the Agency for Healthcare Research and Quality (HS11832). The researchers examined use of certain laboratory tests for seven medications commonly used to prevent or treat cardiovascular disease in older people: angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), amiodarone, digoxin, diuretics, potassium supplements, and statins.

They investigated whether nearly 200,000 elderly members of 10 HMOs, who received 1 of these high-risk cardiovascular medications as outpatients, had the recommended baseline laboratory monitoring performed during the 180 days before or 14 days after the drug was initially dispensed. Lack of laboratory monitoring varied by medication class. For example, 23 percent of patients who were prescribed potassium supplements did not receive serum potassium and serum creatinine monitoring; 58 percent of patients prescribed amiodarone did not have recommended monitoring for thyroid or liver function.

Recommended laboratory tests were most likely to be omitted in the youngest elderly for ACE inhibitors, ARBs, digoxin, diuretics, and potassium supplementation. However, in patients receiving amiodarone and statins, recommended laboratory tests were most often omitted in the oldest elderly. Laboratory tests were also more likely to be omitted in patients with fewer coexisting medical problems. Average error rates (recommended laboratory tests not performed) ranged from 23 to 43 percent at various sites. The study did not examine the association between laboratory monitoring errors and adverse clinical outcomes.

See "Baseline laboratory monitoring of cardiovascular medications in elderly health maintenance organization enrollees," by Steven R. Simon, M.D., M.P.H., Susan E. Andrade, Sc.D., Jennifer L. Ellis, M.S.P.H., and others, in the December 2005 Journal of the American Geriatrics Society 53(12), pp. 2165-2169.

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