Identifying potential predictors of high-quality oral anticoagulation assessed by time in therapeutic international normalized ratio range: a prospective, long-term, single-center, observational study

Abstract

Background: The efficacy and risks of oral anticoagulation are largely associated with maintaining the quality of anticoagulation control. Nevertheless, few studies have addressed which factors, if any, are associated with this control.

Objective: This study aimed to identify predictors of high-quality oral anticoagulation.

Methods: A prospective observational study enrolled all adult patients on intended long-term oral anticoagulation attending a public anticoagulation clinic. Patients with high-quality anticoagulation, defined as percentage of time in therapeutic international normalized ratio (INR) range (TTR) ≥66%, were compared with those with poor anticoagulation control (TTR <66%). Measures included cognitive, psychological, and relevant behavioral factors, in addition to traditionally implicated ones, such as age, comorbidity, and concurrent medications.

Results: Participation was requested from all 233 patients followed up at the anticoagulation clinic. Eighty-six did not meet the inclusion criteria (49 due to intended anticoagulation duration <90 days, 37 due to the need for a caregiver responsible for medications). A total of 147 patients were enrolled, of whom 13 (8.8%) were lost to follow-up. Therefore, data were analyzed from 134 patients (mean [SD] age, 55 [14.2] years [range, 19-87 years]), who were followed up for a mean (SD) duration of 272 (87) days. The total mean TTR was 64.7%, which is comparable to values achieved in clinical trials. The good-control group had 61 patients (45.5%) (mean TTR, 77.7% [8.5%]) and the poor-control group had 73 patients (54.5%) (mean TTR, 50.4 [11.7%]). On multivariate logistic regression analysis, high-quality anticoagulation was independently associated with regular vitamin K intake, expressed by its variability in daily dosage (odds ratio [OR] = 0.79; 95% CI, 0.64-0.98); male sex (OR = 2.41; 95% CI, 1.06-5.49); duration of anticoagulation treatment >2 months (OR = 3.23; 95% CI, 1.25-8.36); presence of family support (OR = 3.32; 95% CI, 1.16-9.48); functional and cognitive ability to take medications as prescribed, defined as good medication management capacity (MMC; as assed using the Drug Regimen Unassisted Grading Scale) (OR = 4.18; 95% CI, 1.63-10.68); and no regular use of alcohol (OR = 8.59; 95% CI, 1.45-51.09).

Conclusions: The data suggest that independent predictors of high-quality oral anticoagulation included regular vitamin K intake, male sex, duration of anticoagulation treatment >2 months, presence of family support, good MMC, and no regular alcohol use. These findings may help clinicians to decide whether to start anticoagulation in intermediate-risk patients, to identify patients who will require closer attention on their anticoagulation management, and to direct their efforts to improve the quality of oral anticoagulation.