We appreciate the thoughtful comments of Dr. Ginier and colleagues. We agree that absence of seasonal variation in the complication rate does not prove that alterations in dietary intake of these foods cannot cause fluctuations in the PTR. However, in geographic locations where these vegetables are available year-round, patients would need to drastically alter their intake for other reasons to induce wide swings in anticoagulation control. We have observed occasional instances of this phenomenon, but our study suggests that other factors are more important causes of variability in the PTR.

We also do not discount the potential for other medications to interfere with anticoagulation control. We were, however, quite encouraged by the results of our study, which indicate that when patients are carefully managed, as they were in our participating clinics, this is uncommon. In large part, this was probably due to the fact that patients in all the clinics were usually instructed to begin no new medications from any source without first checking with the anticoagulation clinic. We do not suppose that these results can be generalized to institutions where patients are being managed without a protocol and by inexperienced practitioners.

Although one study showed that warfarin anticoagulation can be managed safely, warfarin remains a drug with the potential for serious complications. Patients receiving this medication require extensive education and meticulous management. In large institutions, this can usually be accomplished most effectively and efficiently in a dedicated anticoagulation clinic operating within accepted guidelines [1].