Warfarin Institute of America
Dedicated to Your Health
EXPERIENCES WITH A PHARMACIST-DIRECTED ANTICOAGULATION CLINIC
During 1999, 345 people made 2,542 visits to the clinic. This accounted for 181.7 patient years. During this time there were 159 minor and 1 major bleeding incidents. There were eight events when patients had real of suspected blood clots but all turned out to be minor. The patients made an average of 14 visits to the clinic during the year. Thus they were monitored just slightly more frequently than once per month on average. The patients had their INRs in the therapeutic range at 58.7 % of all visits.
The one major bleeding incident was gastrointestinal and was precipitated by the patient visiting relatives in a third-world country. He returned home with bloody vomiting and diarrhea. He recovered from this incident but was never re-started on warfarin and subsequently died several months later.
When people had an INR of 5.0 or higher, they had an 18.6% chance of minor bleeding before the INR was brought down. When people had an INR of 1.0 to 3.5, they had a 5.7 chance of minor bleeding during the year. Thus, the group with the higher INR was significantly more likely to bleed (p < 0.001).
When people had an INR between 3.6 and 4.9, they had a 7.6% chance of minor bleeding during the year. Comparing this group to the people who had INRs of 5.0 or higher, the lower group was significantly less likely to bleed (p=0.003).
Those who had a target INR of 3.0 (desired range 2.5 to 3.5) had a significantly higher risk of bleeding than those whose INR target was 2.5 (range 2.0 to 3.0) (p=0.001).
It should be noted that among all of the groups, the risk of bleeding was less than 1 in 5. Also at 74.5% of the visits where minor bleeding was reported, the INR was at or below the therapeutic range.
The assistance of Mack Thomas, Ph.D. Statistician, Blari Presti, M.D. Pathologist and John Stachler, M.D. Cardiologist is acknowledged.
We also have surveyed patients and physicians as to their satisfaction with the clinic. The patient's reported that they were most satisfied with the finger-stick method of obtaining blood samples. They also appreciated appointments being kept on time and the information provided by the pharmacist being helpful. The fact that 75% of the patients responded to the direct-mail questionnaire also indicates their support. We had 51% of the physicians respond to their questionnaires. Their most positive responses were that their patients were expressing positive reactions to the clinic and the the information from the pharmacist was timely and complete.
The assistance of Daniel C. Malone, Ph.D. of the University of Arizona College of Pharmacy is acknowledged.
Another study looked at about 12,000 patient visits to our clinic over four years. We found that minor bleeding (usually a nosebleed but some were from the bowel or bladder) occurred about once every 1.5 patient-years. Major bleeding (requiring two or more units of blood or any bleeding into the brain) occurred about once every 33 patient-years. Clotting (all clots were considered major and included anything from the legs to the brain) occurred about once every 100 patient-years. What does this mean? If you are starting on warfarin, there is a good chance that you will have a nosebleed - they occur about once for every 18 months of therapy. There is very little chance that you will have a major bleed, even if you are told to take it for the rest of your life. The chance is tiny that you will have another clot or a stroke while on warfarin. The only exception might be if you have antiphospholipid antibody syndrome since these people probably accounted for most of the clots.
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Last updated August 29, 2004