A computerized intervention to improve timing of outpatient follow-up: a multicenter randomized trial in patients treated with warfarin. National Consortium of Anticoagulation Clinics

J Gen Intern Med. 1994 Mar;9(3):131-9. doi: 10.1007/BF02600026.


Objective: To evaluate a computerized scheduling model that employs nonlinear optimization to recommend optimal follow-up intervals for patients taking warfarin.

Design: Randomized trial.

Setting: 5 anticoagulation clinics.

Patients/participants: 620 patients expected to receive warfarin for > or = 6 weeks.

Interventions: Computer-generated recommendations for scheduling the next visit were presented to or withheld from practitioners.

Measurements and main results: The main outcome measures were the follow-up interval scheduled by the provider, the interval at which the patient actually returned to clinic, and the quality of anticoagulation control (computed as the absolute difference between the measured and target prothrombin times [PTRs] or international normalized ratios [INRs]). Follow-up intervals scheduled for the patients whose practitioners received computer-generated recommendations were significantly longer than those for control patients (mean, 4.4 vs 3.5 weeks, p < 0.001), despite the fact that the practitioners modified the suggested return interval by > 1 week on 40% of the visits. The interval at which the intervention group actually returned to clinic was also longer (mean, 4.4 vs 4.1 weeks, p < 0.05), even though the control patients tended to return at longer intervals than were scheduled by their practitioners. Control of anticoagulation was nearly the same among experimental and control patients. Life-threatening complications occurred in the care of three experimental patients and one control patient, while other serious complications occurred in the care of 16 experimental patients and 17 control patients.

Conclusions: Recommendations based on nonlinear optimization prompted clinicians to schedule less frequent follow-up for patients taking warfarin, with no deterioration in anticoagulation control. This approach to scheduling can potentially reduce utilization while maintaining quality of care for patients who require long-term monitoring.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Appointments and Schedules*
  • Continuity of Patient Care / standards
  • Drug Therapy, Computer-Assisted*
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Middle Aged
  • Monitoring, Physiologic / methods*
  • Prothrombin Time
  • Warfarin / therapeutic use*


  • Warfarin