Which method is considered an objective measure of a patient’s adherence to a prescribed medication plan?

• A. Measurement of drug titers in body fluids
• B. Self-report
• C. Diaries
• D. Electronic medication monitors

Answer: (A)

Measuring drug levels in body fluids provides an objective check of actual medication exposure, independent of what the patient reports or how devices behave. A detectable drug concentration in blood or urine indicates that the medication was ingested and absorbed, making it a biochemical, quantitative measure of adherence.

Self-report and diaries rely on patient memory and honesty, which can lead to inaccuracies. Electronic medication monitors track when a bottle is opened, but opening the bottle doesn’t guarantee that a dose was taken or absorbed. Drug titers, while influenced by timing and metabolism, offer the most direct, objective evidence of adherence among these options.