Objective Recommendations for routine laboratory monitoring to reduce the risk of adverse medication events are not consistently followed. We evaluated the impact of electronic reminders delivered to primary care physicians on rates of appropriate routine medication laboratory monitoring.

Design We enrolled 303 primary care physicians caring for 1,922 patients across 20 ambulatory clinics that had at least one overdue routine laboratory test for a given medication between January and June 2004. Clinics were randomized so that physicians received either usual care or electronic reminders at the time of office visits focused on potassium, creatinine, liver function, thyroid function, and therapeutic drug levels.

Measurements Primary outcomes were the receipt of recommended laboratory monitoring within 14 days following an outpatient clinic visit. The effect of the intervention was assessed for each reminder after adjusting for clustering within clinics, as well as patient and provider characteristics.

Results Medication-laboratory monitoring non-compliance ranged from 1.6% (potassium monitoring with potassium-supplement use) to 6.3% (liver function monitoring with HMG CoA Reductase Inhibitor use). Rates of appropriate laboratory monitoring following an outpatient visit ranged from 14% (therapeutic drug levels) to 64% (potassium monitoring with potassium-sparing diuretic use). Reminders for appropriate laboratory monitoring had no impact on rates of receiving appropriate testing for creatinine, potassium, liver function, renal function, or therapeutic drug level monitoring.

Conclusion We identified high rates of appropriate laboratory monitoring, and electronic reminders did not significantly improve these monitoring rates. Future studies should focus on settings with lower baseline adherence rates and alternate drug-laboratory combinations.