Fibbers

Abstract & Commentary

Synopsis: Only about 12% of patients with new onset atrial fibrillation who did not have apparent contraindications to warfarin treatment filled prescriptions for it.

Source: Johnson JA, et al. Arch Intern Med. 2003;163:1705-1710.

This was a retrospective review of Ohio Medicaid billing data conducted in 1998-2000. There were 11,699 cases of new-onset nonvalvular atrial fibrillation (AF) during that time period. Johnson and colleagues collected and controlled for risk factors for stroke and hemorrhage, as well as many other medical conditions and some socioedemographic factors thought to be relevant. Analysis of data from all providers of medical services to Ohio Medicaid enrollees revealed that only 9.7% of all patients with new-onset AF and only 11.9% of those without apparent contraindications filled prescriptions for warfarin in the 7 days preceding or 30 days following the documented date of diagnosis of AF. Hypertension and congestive heart failure predicted increased likelihood of using warfarin. Age younger than 55 or older than 85 years predicted nontreatment, as did prior intracranial hemorrhage, prior gastrointestinal hemorrhage, predisposition to falls, alcohol, or other drug use, renal impairment, and conditions perceived as barriers to compliance.

Comment by Barbara A. Phillips, MD, MSPH

I confess that when I first read this title and skimmed this abstract, I thought this paper was about patient acceptance and compliance with medical therapy. It’s not. It’s about physician compliance with guidelines. Bear with me; it’s not as bad as you may be thinking.

The thrust of the article appears to be that there must be something different about the way physicians treat women, Ohioans, or Medicaid patients. In this study, only about 12% of eligible patients with new-onset atrial fibrillation were prescribed warfarin. This is in stark contrast to studies showing that eligible patients with new AF in the Kaiser Permanente system in Northern California1 and in the Harvard Community Health Plan2 received it 55% and 79% of the time, respectively. The difference is unlikely to be due to the fact that the patients were women; the Medicaid population reported here is about 69% women overall and about 78% women for the group older than 75. The difference is also unlikely to be due to the fact that the study was done in Ohio. As a Kentuckian, I have lived next to Ohio most of my life. They have their quirks, of course, but Buckeye people are pretty much like the rest of us.

So it must be because they are Medicaid recipients that so few patients who might have been expected to benefit from warfarin treatment received it. Johnson et al are careful to point out that they tried to identify known contraindications to anticoagulation such as alcoholism, prior hemorrhage, and falling risk. Patients with these risks were not considered "eligible" and were not part of the 88% of patients with new AF who did not get treated.

One of the most robust predictors of nontreatment with warfarin in this study was what Johnson et al called "Perceived barriers to compliance," defined as mental illness, homelessness, inadequate housing, lack of a caregiver, or known noncompliance. About 30% of patients in this population had one or more of these barriers, and their presence strongly predicted nontreatment with warfarin.

Those of us who have cared for patients on warfarin know that it takes partnership and commitment on both sides. Appointments must be kept, blood levels must be monitored, medication must be taken regularly, and diet, alcohol, and other medication intake needs to be consistent for the titration to be accurate. Anticoagulant overdose is messy, dangerous business, and no physician wants to be part of it. It is also possible—even likely—that the Ohio doctors wrote far more prescriptions for warfarin than patients filled. Johnson et al make little note of the possibility that some patients in this study may simply have failed to fill a prescription, but that is extremely likely. Some data suggest that only about two-thirds of prescriptions that physicians write get filled in a timely manner. So I have some empathy and understanding for those Buckeye MDs who erred on the side of doing no harm in the case of patients who seemed unlikely to be able to be partners in their own care and who probably wrote some prescriptions that never got filled.

On the other hand, this study and others have consistently found that advancing age is strongly associated with reduced likelihood of receiving anticoagulation. This is despite the fact that the risk of AF rises impressively with aging, as does the risk of its most common adverse consequence, strokes. Although the risk of hemorrhage with warfarin is real, substantial evidence indicates that its benefits far outweigh its risks, especially in people older than 75.4,5 Perhaps the real message from this paper is to reconsider the use of warfarin in those who might appear to be "too old."

Dr. Phillips, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington, KY, is Associate Editor of Internal Medicine Alert.

References

1. Go AS, et al. Ann Intern Med. 1999;133:927-934.

2. Gottlieb LK, Salem-Sanches S. Arch Intern Med. 1994;154:1945-1953.

3. Enlund H, et al. Acta Med Scand. 1981;209:271-275.

4. Lightowlers S, McGuire A. Stroke. 1998;29:1827-1832.

5. Albers GW, et al. Chest. 2001;119(1 Suppl):194S-206S.