Therapeutic drug monitoring (TDM) tests help evaluate if prescribed, high-risk medications are working safely and effectively, and they can help assess the patient’s health—yet they are not always performed as recommended. A study in the Journal of General Internal Medicine determined that a patient’s overall health as well as the physician's characteristics can affect whether the physician orders these necessary tests.

In this study, the authors evaluated electronic medical records involving 31,417 patients and 278 medical providers at the Meyers Primary Care Institute in Massachusetts. This resulted in data for prescriptions for 34 high-risk medical conditions and 60 tests associated with them.

“For recommended tests, the rate of physician ordering varies greatly, with for example almost all patients taking potassium receiving an order for a potassium level (95 percent) but less than half of patients on Lithium receiving orders for a blood count (42 percent) or creatinine level (49 percent), as is recommended,” states a summary of the study. “Tests measured yearly (for example, Digoxin level) were more likely to be ordered than those required more often (for example, AST/ALT levels in patients on Rifampin).”

The researchers also identified certain correlations between provider and patient characteristics and test-ordering practices: specialists, younger physicians, and clinicians who are familiar with the testing guidelines for a specific medication were more likely to order recommended tests. Patients who were male, or older, were tested more often than other patients. Additionally, black box warnings on certain medications were connected with higher ordering rates. However, healthier, “younger patients, and people who do not often visit doctors seldom received test orders,” states Springer.

These findings suggest that provider education and reminders about the need to administer tests could help improve TDM rates. Interventions to improve TDM should also “focus on areas with the greatest potential for improvement, such as providers who do not prescribe medication much, or those who prescribe medication to healthier and younger patients, or once-off walk-in patients,” says lead study author Shira Fischer, a clinical informatics fellow at the Beth Israel Deaconess Medical Center in Boston.

Read the full study online.