Ml. Brigden et al., AUDIT OF THE FREQUENCY AND CLINICAL-RESPONSE TO EXCESSIVE ORAL ANTICOAGULATION IN AN OUTPATIENT POPULATION, American journal of hematology, 59(1), 1998, pp. 22-27
A retrospective review of over-anticoagulated patients with critical i
nternational normalized ratios (INRs) was undertaken in a large outpat
ient laboratory. In the six-month study period, 85 prothrombin times (
PTs) were identified with an INR of greater than or equal to 6.0, an o
verall incidence of elevated PTs of 0.2% or two per 1,000 INR tests. C
omplete follow-up data was available on 65 patients. When compared to
an age- and gender-matched control group without INR greater than or e
qual to 6.0, high-INR patients were significantly more likely to manif
est the presence of alcoholism or liver disease, to have been anticoag
ulated for less than six months, to have experienced more frequent war
farin dosage changes, and to have had the addition of a medication kno
wn to interact with warfarin, In the high-INR group, a likely cause fo
r the specific critical INR was identified in 44 patients (68%). Drug
interactions followed by compliance problems were the most common fact
ors identified. The 13 patients (20%) who received vitamin K therapy e
xperienced no difference in the clinical outcome compared with those m
anaged conservatively. Conservative management of critically high INR
values appeared to be as efficacious as intervention with vitamin K th
erapy. (C) 1998 Wiley-Liss, Inc.