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Preventing Medication Errors in Ambulatory Care: The Importance of Establishing Regimen Concordance.


In: Henriksen K1, Battles JB1, Marks ES2, Lewin DI1, editors.


Advances in Patient Safety: From Research to Implementation (Volume 1: Research Findings). Rockville (MD): Agency for Healthcare Research and Quality (US); 2005 Feb.
Advances in Patient Safety.

Author information

Agency for Healthcare Research and Quality
US Department of Defense
University of California, San Francisco Primary Care Research Center (DS, EM, FW, MR, AB), San Francisco General Hospital (DS, EM, FW, MR, AB)


Objective: Miscommunications between patients and providers can have serious consequences—especially where medications are concerned. Because oral anticoagulants are associated with preventable adverse events at disproportionately high rates, we used the model of anticoagulant care to examine the extent to which regimen discordance between patient and provider contributes to unsafe medication management. Methods: We performed a study among 220 long-term users of warfarin in an anticoagulation clinic to characterize the importance of two medication assessment components. We measured (1) adherence to warfarin by asking patients to report any missed doses during the prior 30 days, and (2) concordance between patients' and providers' reports of prescribed warfarin regimens. We categorized patients as having complete adherence if they missed no doses and regimen concordance if there was patient-provider agreement in the total weekly dosage. We examined the independent relationships between (a) adherence and anticoagulant outcomes, and (b) concordance and anticoagulant outcomes. We characterized anticoagulant outcomes as unsafe if international normalized ratio (INR) values either were < 2.0 (at risk for thrombosis) or > 4.0 (at risk for hemorrhage) over 90 days, using repeated measures analysis. Results: One hundred fifty-five patients (70.5 percent) reported no missed warfarin doses during the prior 30 days. In multivariate models, poor adherence was associated with under-anticoagulation (adjusted odds ratio [AOR] = 2.33; 95% confidence interval [CI] = 1.56–3.45; P < 0.001), but not with over-anticoagulation (AOR = 1.36; 95% CI = 0.69–2.66; P = 0.38). One hundred ten patients (50 percent) reported warfarin regimens that were discordant with respect to the clinicians' report. Among adherent patients, discordance was associated with both under-anticoagulation (AOR = 1.67; 95% CI = 1.00–2.78; P = 0.05) and over-anticoagulation (AOR = 3.44; 95% CI = 1.32–9.09; P = 0.01). There was no relationship between patients' reports of adherence and concordance (odds ratio [OR] = 1.14 95% CI = 0.64–2.04; P = 0.66). Conclusion: Discordance between clinicians and patients regarding warfarin regimens is unsettlingly common and places patients at risk for thromboembolic and hemorrhagic events. To promote safe and effective care, clinicians should sequentially determine adherence (missed doses) and regimen concordance during routine medication assessments. Systems need to be developed to ensure patient-provider concordance in medication regimens.

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