Analysis of risk factors for over-anticoagulation in patients receiving long-term warfarin.
A cohort of patients with an INR >7.0 were identified prospectively and compared with a group of patients with stable anticoagulant control. During the study 15,100 INR measurements were recorded and 31 (0.2%) were >7.0. Odds ratios of patient characteristics were calculated as an estimate of relative risk for the development of a high INR. The highest risk factor was a target INR of 3.5 (OR 7.3, 95% CI 2.6-20.2). The second highest risk factor was antibiotic therapy in the 4 weeks preceding the high INR (OR 6.2, 95% CI 1.4-27.7). Bleeding was reported more frequently in the high INR group (OR 5.4, 95% CI 2.1-13.9). Five major bleeds occurred in this group compared to none in the stable group. This analysis identifies risk factors for over-anticoagulation and hence when to intensify monitoring and when to consider pre-emptive warfarin dose reductions.
Panneerselvam
S
S
Department of Haematology, Addenbrooke's NHS Trust, Cambridge.
Baglin
C
C
Lefort
W
W
Baglin
T
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects*; D001777:Blood Coagulation / Q000187:drug effects; D004334:Drug Administration Schedule; D004347:Drug Interactions; D006470:Hemorrhage / Q000139:chemically induced*; D006801:Humans; D019934:International Normalized Ratio; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D014859:Warfarin / Q000008:administration & dosage / Q000009:adverse effects*
D000900:Anti-Bacterial Agents; D000925:Anticoagulants; D014859:Warfarin