Assessment of Therapeutic Control of Anticoagulation

Abstract

The control achieved in two anticoagulant clinics over 1 year was studied. The result of 430 patient years of treatment in 732 patients was assessed. Overall, the patients were maintained in the therapeutic range (British ratio 2.0–4.0) 85% of the time, ‘under-anticoagulated’ 10% and ‘overtreated’ 5% of the time. Patients on long-term treatment had better control than those on short-term treatment (87 and 72% of time in therapeutic range, respectively). Short-term patients were ‘undertreated’ one quarter of the time. Assessment of the percentage of time individual patients spent within the therapeutic range was a useful index: 77% short-term patients and 99% long-term patients were controlled more than half the time; and 30% short-term plus 40% long-term patients were controlled all the time. Two complementary methods of assessing therapeutic control are used. The standard of control compares favourably with other reports, but shows areas where improvements can be made. For assessment of clinical benefit from anticoagulants, close quality control of treatment by such methods is essential.

Time to Revisit the Time in the Therapeutic Range

“…[4] ); and more [ Table 1]. Thus, as a means of assessing the stability of warfarin anticoagulation (often used synonymously with the adequacy of anticoagulation), the Time in the Therapeutic Range (TTR) [5] has become a common reportable measure in clinical trials. TTR is presumed to represent the percent of time the INR remains in the target range across time.…”

“…[11] If the same geographical differences in recheck frequency (often reflecting access to care, local traditions, source of payment for care, and more) occurred in trials D and E as occurred in ROCKET-AF, then could we truly compare the mean TTR values in trial D to those in trial E? (5)In trial F, all patients receive all of their care from the physicians in the trial centers. In trial G, patients receive care from their trial physicians as well as from their individual primary care physicians.…”

Laboratory Control, Optimal Therapeutic Ranges and Therapeutic Quality Control in Oral Anticoagulation

“…In June 1984, Copplestone and Roath [1] reported, in this journal, an oustandingly high rate of compli ance with the therapeutic range of the prothrombin times of patients under the supervision of their 2 out patient anticoagulant clinics. On closer scrutiny, how ever, the authors' data are misleading, as pointed out by Duxbury [2] in his recent Letter to the Editor of this journal: the therapeutic range adopted by Copplestone and Roath was the all-embracing range of 2-4 British ratios (which for this range is identical to the Interna tional normalized ratio) as proposed by the British Society of Haematology in 1977 [3].…”

“…Figure 3 shows that British thrombosis centres have successfully implemented the 1977 British recommendations [1,5,42]: the prothrombin times found by all centres were within range more than 80% of the time. This means that with the British system of monitoring oral anti coagulation, adequate prevention of (recurrent) ve nous thrombosis can be achieved quite easily.…”

Management of anticoagulant therapy: The dutch experience

“…There are several ways to express the success of this effort [4][5][6]. A simple proportion of INRs within the therapeutic ränge gives an unduly pessimistic result because patients who are unstable are seen most often [7].…”