Table 9.2. Inpatient anticoagulation services and outpatient anticoagulation clinics*

StudyStudy Design, OutcomesResults
Ansell, 1996 30
Pooled comparison of anticoagulation clinics and routine medical care
Pooled results from 6 Level 3 study designs comparinganticoagulation clinics with routine medical care31-36 (Level 3A)
Major bleeding and thromboembolic events (Level 1)
Major bleeding events per patient-year: anticoagulation clinic, 0.028 (95% CI: 0-0.069) vs. routine care, 0.109 (95% CI: 0.043-0.268)
Thromboembolic events per patient-year: anticoagulation clinic, 0.024 (95% CI: 0-0.08) vs. routine care, 0.162 (95% CI: 0.062-0.486)
Hamby, 2000 29
Analysis of adverse events related to outpatient warfarin therapy among 395 patients followed at a Veterans Affairs Hospital, with 306 enrolled in an anticoagulation clinic and 89 patients receiving usual care
Case-control study (Level 3)
Adverse events related to under- or over-anticoagulation (Level 1)
Among the 12 patients with preventable adverse events related to anticoagulation, 8 were not enrolled in the anticoagulation clinic
Patients receiving usual care had 20 times the relative risk (95% CI: 6-62) of an adverse event compared with patients in the anticoagulation clinic.
Lee, 1996 26
Comparison of pharmacist-managed anticoagulation clinic with patient receiving usual care
Retrospective cohort comparison (Level 3)
Hospital admissions related to under- or over-anticoagulation - ie, thromboembolic or bleeding events (Level 1)**
Patients in anticoagulation clinic had non-significant reductions in hospital admissions related to thromboembolic or bleeding events compared with control group***
Ellis, 1992 37
Pharmacy-managed inpatient anticoagulation service (flow sheet for monitoring, but no nomogram) for monitoring patients receiving warfarin for a variety of indications
Retrospective before-after analysis (Level 3)
Anticoagulation "stability" at discharge and odds of therapeutic anticoagulation at first outpatient visit (Level 2)
Patients receiving the intervention were more likely to have PT "stability" at discharge: 61.5% vs. 42.3% (p=0.02)
Odds of having therapeutic PT at first outpatient clinic visit with intervention: OR 5.4 (95% CI: 1.87-15.86)
Gaughan, 2000 24
Anticoagulation clinic for outpatients receiving warfarin for atrial fibrillation (managed by nurse practitioner using warfarin dosing nomogram)
Retrospective before-after analysis (Level 3)
Percentage of patients in the desired range for anticoagulation (Level 2) was evaluated as a secondary outcome
Minor increase in percentage of patients with INR in desired range: 53.7% vs. 49.1% (p<0.05, but questionable clinical significance)
Radley, 1995 27
Performance of pharmacist-run hospital-based outpatient anticoagulation clinic in England compared with historical control (management by rotating physician trainees)
Retrospective before-after analysis (Level 3)
Proportions of INR measurements "in" or "out" of the therapeutic range
No significant difference for patients with stable INR in the baseline period, but patients with an INR result "out" of range were more likely to return to "in" range under anticoagulation clinic management compared with routine physician management
Rivey, 1993 22
Pharmacy-managed inpatient anticoagulation service (using weight-based heparin protocol) for medicine inpatients compared with older fixed-dose protocol without any active management by pharmacists
Before-after analysis (Level 3)
Time to therapeutic PTT (Level 2)
Time to therapeutic PTT was less with nomogram protocol: 40 vs. 20 hours (p<0.05)
Fewer supra-therapeutic PTTs with protocol: 1.7 vs. 5.5 (p<0.05)
Bleeding rates: no difference but numbers were small

* CI indicates confidence interval; INR, international normalized ratio; OR, odds ratio; PT, prothrombin time; and PTT, partial thromboplastin time.

** We counted this outcome as Level 1, but it is important to note that authors did not capture all of the designated clinical events, just those that resulted in admissions to the study hospital.

*** Using the results reported in the study, we calculated the 95% CIs for admissions related to thromboembolic events (intervention, 0.2-18.5%; usual care, 12.7-42.5%) and bleeding events (inervention, 1.1-22.8%; usual care, 7-33.4%).

From: 9, Protocols for High-Risk Drugs: Reducing Adverse Drug Events Related to Anticoagulants

Cover of Making Health Care Safer
Making Health Care Safer: A Critical Analysis of Patient Safety Practices.
Evidence Reports/Technology Assessments, No. 43.
Shojania KG, Duncan BW, McDonald KM, et al., editors.

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