Assessment of Therapeutic Quality Control in a Long-Term Anticoagulant Trial in Post-Myocardial Infarction Patients

Abstract

SummaryVarious methods have been described to evaluate efficacy of anticoagulant therapy using the international normalized ration (INR). We compared the following approaches: (1) total INR’s or the most recent measurement; (2) percent time within therapeutic range, with INR changing directly or halfway between visits; and (3) total observation time assuming INR changing linearly. The study population comprised 1700 post myocardial infarction patients. Treatment comprised 3725 patient-years. There were 61,471 INR assessments with target therapeutic level of 2.8–4.8. Acenocoumarol as well as phenprocoumon were employed. Therapeutic achievement in the first months of treatment was low: less than 60% of INR’s were in range. Treatment stabilized after 6 months. Patients on acenocoumarol were within range 70% of the time compared to 80% for phenprocoumon. Method 3 is preferred because it incorporates time and is capable of calculating incidence rates at different INR levels. Our findings call for an urgent improvement of standard of anticoagulant control in the first months following commencement of treatment.

Quality of oral anticoagulant therapy in patients who perform self management: warfarin versus phenprocoumon

“…The TTR was estimated by the ''Rosendaal-method'', which assume a linear change between successive INR measurements when calculating the proportion of time during each interval that was spent in-range in relation to the total duration of therapy [16].…”

Self-Management of Oral Anticoagulant Therapy: A Review

“…Time within therapeutic INR target range can be estimated with various methods giving different results [13,22,[28][29][30]. Four different methods have been used, namely proportion, cross-section, equidivision and linear interpolation [22,28,30].…”

“…Four different methods have been used, namely proportion, cross-section, equidivision and linear interpolation [22,28,30]. Today, the preferred method is linear interpolation, 3 the socalled "Rosendaal-method" [29,30]. It is the most precise method and the most conservative, since it underestimates time within therapeutic INR target range compared to the other methods [29].…”

Efficacy of inferior vena cava filters in anticoagulated patients

“…Other common reasons for filter insertion were non-compliance, fall risk, and dementia. TTRs were somewhat lower than for the full cohorts (40.8% for the AC-Only patients vs. 38.2% for the AC-Filter patients) as assessed by mid-duration range to midduration INR [9]. There was only one PE in these matched cohorts, in a patient with a filter who had not been a Ôrecurrent VTEÕ or a prior Ômassive PEÕ, so no outcome data on PE could be determined.…”

“…For the IVC filter group, indications for filter placement, types of devices inserted and procedurerelated adverse events (operative complications, IVC thrombosis, filter fractures, migration, IVC penetration) were also investigated. For analyses of these smaller matched subsets, TTRs (with target INR of 2.5) were calculated from midpoint to midpoint duration of INR values by the method of Rosendaal [9], and were considered Ôin-rangeÕ for values of 2.0-3.0 and Ôhigh-in-rangeÕ for values of 3.1-3.5.…”