Relationship between test frequency and outcomes of anticoagulation: a literature review and commentary with implications for the design of randomized trials of patient self-management

Guidelines for implementation of patient self-testing and patient self-management of oral anticoagulation. International consensus guidelines prepared by International Self-Monitoring Association for Oral Anticoagulation

AIMS

This document provides health care professionals involved in initiating and monitoring oral anticoagulation therapy with guidelines for the provision of safe and effective patient self-testing/patient self-management of oral anticoagulation.

METHODS AND RESULTS

The consensus group has critically reviewed the literature and compared the results of usual care (UC) vs. anticoagulation clinic and patient self-management/patient self-testing (PSM/PST). The education and training of patients for self-monitoring are described, together with the suitability of patients, the effect on quality of life and cost-effectiveness. The consensus agrees that patient self-testing and patient self-management are effective methods of monitoring oral anticoagulation therapy, providing outcomes at least as good as, and possibly better than, those achieved with an anticoagulation clinic. All patients must be appropriately selected and trained. Currently available self-testing/self-management devices give INR results which are comparable with those obtained in laboratory testing. The most frequent testing frequency is weekly but lower frequency of testing can be justified based on institutional or patient conditions.

CONCLUSIONS

The consensus agrees that there are several points in favour of PST/PSM, for example, a higher degree of medical safety, increased patient education, improved response to changes in lifestyle, increased independence for the patient and improved quality of life.

The Impact of Patient Self-Testing of Prothrombin Time for Managing Anticoagulation: Rationale and Design of VA Cooperative Study #481—The Home INR Study (THINRS)

BACKGROUND

Anticoagulation (AC) with warfarin reduces the risk of thromboembolism (TE) in a variety of applications, yet despite compelling evidence of the value and importance of high quality AC, warfarin remains underused, and dosing is often suboptimal. Approaches to improve AC quality include (1) an AC service (ACS), which allows the physician to delegate day-to-day details of AC management to another provider dedicated to AC care, and (2) incorporating into the treatment plan patient self-testing (PST) under which, after completing a training program, patients perform their own blood testing (typically, using a finger-stick blood analyzer), have dosage adjustments guided by a standard protocol, and forward test results, dosing and other information to the provider. Studies have suggested that PST can improve the quality of AC and perhaps lower TE and bleed rates. The purpose of Department of Veterans Affairs (VA) Cooperative Studies Program (CSP) #481, "The Home INR Study" (THINRS) is to compare AC management with frequent PST using a home monitoring device to high quality AC management (HQACM) implemented by an ACS with conventional monitoring of prothrombin time by international normalized ratio (INR) on major health outcomes. PST in THINRS involves use of an INR monitoring device that is FDA approved for home use.

STUDY DESIGN

Sites are VA Medical Centers where the ACS has an active roster of more than 400 patients. THINRS includes patients with atrial fibrillation (AF) and/or mechanical heart valve (MHV) expected to be anticoagulated indefinitely. THINRS has two parts. In Part 1, candidates for PST are evaluated for 2 to 4 weeks for their ability to use home monitoring devices. In Part 2, individuals capable of performing PST are randomized to (1) HQACM with testing every 4 weeks and as indicated for out of range values, medication/clinical changes, or (2) PST with testing every week and as indicated for out of range values, medication/clinical changes. The primary outcome measure is event rates, defined as the percent of patients who have a stroke, major bleed, or die. Secondary outcomes include total time in range (TTR), other events (myocardial infarction (MI), non-stroke TE, minor bleeds), competence and compliance with PST, satisfaction with AC, AC associated quality of life (QOL), and cost-effectiveness. To assess the effect of PST frequency on TTR and other outcomes, at selected sites patients randomized to perform PST are assigned one of three test frequencies (weekly, twice weekly, or once every four weeks).

[Portable coagulometers: a systematic review of the evidence on self-management of oral anticoagulant treatment]

BACKGROUND AND OBJECTIVE

We aimed to systematically review the scientific evidence about the use of portable coagulometers for patient's self-management of oral anticoagulant treatment.

MATERIAL AND METHOD

Systematic review of scientific evidence available from MEDLINE'S, DARE's, HTA-Database's, NHS-EED's and The Cochrane Library' s bibliographic databases, from their origin to March 2003. Randomized control trials (RCT) and Quasi-Experimental trials were selected provided that they compared patients in self-management with patients under usual care. The quality of scientific evidence was elicited using the Scottish Intercollegiate Guideline Network (SIGN) recommendations, whilst efficacy and security were descriptively summarized.

RESULTS

Twelve (7 RCT and 5 quasi-experimental trials) articles were found, and only two of them provided grade A recommendation. Patients under self-management remained the same or more time in the therapeutic range. The incidence of adverse effects in self-management patients was the same or less than that in patients under usual care.

CONCLUSIONS

The quality of the scientific evidence is heterogeneous. For selected patients, patient's self-management is at least as effective and safe as usual care. New oral anticaogulants, which have shown promising results, should be scrutinized for future changes in service provision.

The pharmacology and management of the vitamin K antagonists: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy

This article concerning the pharmacokinetics and pharmacodynamics of vitamin K antagonists (VKAs) is part of the Seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. The article describes the antithrombotic effect of VKAs, the monitoring of anticoagulation intensity, the clinical applications of VKA therapy, and the optimal therapeutic range of VKAs, and provides specific management recommendations. Grade 1 recommendations are strong, and indicate that the benefits do, or do not, outweigh the risks, burdens, and costs. Grade 2 suggests that individual patient's values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this article are the following: for dosing of VKAs, we suggest the initiation of oral anticoagulation therapy with doses between 5 and 10 mg for the first 1 or 2 days for most individuals, with subsequent dosing based on the international normalized ratio (INR) response (Grade 2B). In the elderly and in other patient subgroups with an elevated bleeding risk, we suggest a starting dose at < or = 5 mg (Grade 2C). We recommend basing subsequent doses after the initial two or three doses on the results of INR monitoring (Grade 1C). The article also includes several specific recommendations for the management of patients with INRs above the therapeutic range and for patients requiring invasive procedures. For example, in patients with mild to moderately elevated INRs without major bleeding, we suggest that when vitamin K is to be given it be administered orally rather than subcutaneously (Grade 1A). For the management of patients with a low risk of thromboembolism, we suggest stopping warfarin therapy approximately 4 days before they undergo surgery (Grade 2C). For patients with a high risk of thromboembolism, we suggest stopping warfarin therapy approximately 4 days before surgery, to allow the INR to return to normal, and beginning therapy with full-dose unfractionated heparin or full-dose low-molecular-weight heparin as the INR falls (Grade 2C). In patients undergoing dental procedures, we suggest the use of tranexamic acid mouthwash (Grade 2B) or epsilon amino caproic acid mouthwash without interrupting anticoagulant therapy (Grade 2B) if there is a concern for local bleeding. For most patients who have a lupus inhibitor, we suggest a therapeutic target INR of 2.5 (range, 2.0 to 3.0) [Grade 2B]. In patients with recurrent thromboembolic events with a therapeutic INR or other additional risk factors, we suggest a target INR of 3.0 (range, 2.5 to 3.5) [Grade 2C]. As models of anticoagulation monitoring and management, we recommend that clinicians incorporate patient education, systematic INR testing, tracking, and follow-up, and good communication with patients concerning results and dosing decisions (Grade 1C+).

Home prothrombin time monitoring: a literature analysis

The anticoagulant activity of warfarin sodium is monitored by the prothrombin time (PT) using the international normalized ratio (INR). Standard oral anticoagulant therapy monitoring requires frequent patient visits to physicians' offices and/or laboratories to optimize warfarin dosage. Home PT monitoring by patients can increase testing frequency and may thus decrease complications associated with oral anticoagulant therapy. Clinical studies suggest that home PT monitoring is more effective than uncoordinated management and is as effective as care through specialized anticoagulation clinics for keeping INRs within a therapeutic range. There are accurate and reliable instruments available, but paramount to the success of home PT monitoring is sound patient selection, appropriate patient training, and consistent quality control.

The value of education and self-monitoring in the management of warfarin therapy in older patients with unstable control of anticoagulation

Of 125 patients aged 65 years or over, with atrial fibrillation taking warfarin for at least 12 months, with a standard deviation (SD) of prothrombin time, expressed as the International Normalized Ratio (INR) >0.5 over the previous 6 months, 40 were randomized to continue with usual clinic care and 85 to receive education about warfarin. Of these, 44 were randomized to self-monitor their INR and 41 returned to clinic. Compared with the previous 6 months there was a significant increase in percentage time within the therapeutic range for the 6 months following education [61.1 vs. 70.4; mean difference 8.8; 95% confidence interval (CI): -0.2-17.8; P = 0.054] and following education and self-monitoring (57 vs. 71.1; mean difference 14.1; 95% CI: 6.7-21.5; P < 0.001), compared with those patients following usual clinic care (60.0 vs. 63.2; mean difference 3.2; 95% CI: -7.3-13.7). Using the same comparative periods, the INR SD fell by 0.24 (P < 0.0001) in the group allocated to education and self-monitoring, 0.26 (P < 0.0001) in the group receiving education alone and 0.16 (P = 0.003) in the control group. Inter-group differences were not statistically significant (intervention groups 0.26 +/- 0.30 vs. control 0.16 +/- 0.3, P = 0.10). Quality-of-life measurements and health beliefs about warfarin were unchanged (apart from emotional role limitation) with education or education and self-monitoring. Patient education regarding anticoagulation therapy could be a cost-effective initiative and is worthy of further study.

Literacy and Numeracy Skills and Anticoagulation Control

BACKGROUND

The ability to use printed material to function in society (literacy) and to handle basic numerical concepts (numeracy) may have implications in patients' ability to follow dosing schedules. We examined literacy and numeracy skills among patients on warfarin and explored their association with anticoagulation control.

METHODS AND RESULTS

Patients older than 50 years attending two anticoagulation management units were prospectively enrolled. We measured literacy, numeracy, and international normalized ratio (INR). During a 3-month follow-up period, we calculated the variability of the INR and the amount of time a patient's INR was within his or her therapeutic range, variables associated with bleeding and effectiveness. Among 143 patients, only 75 (52.4%) were able to read health-related words at the eighth grade level or less. Patients' self-reported grade completed was higher than the measured literacy grade level (kappa = 0.21). While 79.0% had completed at least eight grades, only 47.6% had a score at that grade level. Sixty-nine patients answered none or correctly answered fewer than two of the six numeracy questions (48.3%). The INR variability was higher among patients with lower literacy (P = 0.009) and lower numeracy skills (P = 0.004). The time in range was similar among patients at different literacy levels (P = 0.9). Patients with lower numeracy level spent more time above their therapeutic range (P = 0.04) and had a trend of less time spent in range (P = 0.10).

CONCLUSIONS

Low literacy was prevalent among study patients taking warfarin. Low literacy and numeracy were associated with measures of poor anticoagulation control.

Oral Anticoagulation Therapy in Children: Successfully Controlled by Self-Management

BACKGROUND

Children with congenital heart disease and who are on oral anticoagulation therapy present special challenges due to, for example, rapid fluctuations in international normalized ratio (INR) values, interruption in daily life due to frequent hospital/doctor visits, and difficulties and pain to the child in the performance of venipuncture. We hypothesize that oral anticoagulation therapy can be successfully controlled by self-management for this subset of patients. The aim of this study was to assess the treatment quality of self-managed oral anticoagulation therapy as the proportion of time within the therapeutic INR target range in children with congenital heart disease.

METHODS

Children (N = 22) with a mean age of 10.6 years (range, 1.8-18.6 years) and their parents were trained in home blood analysis of INR and in coumarin dosage adjustment. After training, the children were monitored by weekly INR measurements. The therapeutic range in target INR values was +/-0.5. The indications for initiating oral anticoagulation therapy were the presence of a mechanical heart valve (n = 16) and total cavopulmonary connection (n = 6). The children had no physical restrictions.

RESULTS

The mean observation time was 3.6 years (range, 0.9-5.8 years), and the total number of patient-years was 75.4. The patients were within the therapeutic INR target range for a median of 73.1% (range, 30.3%-91.0%) of the observation time. Two children died for reasons not related to the oral anticoagulation therapy. None of the patients experienced thromboembolic or bleeding complications requiring doctor intervention.

CONCLUSION

Self-management of oral anticoagulation therapy is safe and provides a good quality of treatment for selected children with congenital heart disease.

Occurrence and quality of anticoagulant treatment of chronic atrial fibrillation in primary health care in Sweden: a retrospective study on electronic patient records

BACKGROUND

Chronic atrial fibrillation is a prevalent cardiac disorder. The literature indicates varying proportions of those treated with anticoagulants, and varying intensity of anticoagulation. Electronic patient records are providing us with clinical data concerning management of anticoagulant treatment in real-life practice that is useful for audits. We aimed to assess warfarin treatment for chronic atrial fibrillation in primary health care with regard to prevalence, incidence, the proportion treated and the quality of anticoagulation control.

METHODS

Five primary health care centres in Stockholm with a registered population of 75146 participated in a one-year retrospective study of electronic patient records up until May 2000. All patients over 18 years of age with an encounter labelled 'Atrial fibrillation' were identified, and all records of patients on warfarin treatment were manually reviewed. Main outcome measures were number of patients with chronic atrial fibrillation, number of patients on wafarin treatment, and time within the therapeutic prothrombin range.

RESULTS

In total, 419 patients had chronic atrial fibrillation, giving a prevalence of 0.60% (age-adjusted 0.62%), the age group 65 years or older accounted for 91.6%, and 50.1% were women. Out of these, 50.4% (211 patients) were established on warfarin treatment for chronic atrial fibrillation (0.28% of the population), and there was a predominance of men (p = 0.02). Fifty-four patients started treatment with warfarin for chronic atrial fibrillation (0.07% of the population). Among 25 randomly selected patients on established treatment, the proportion of time within the therapeutic range was 70.2%. Among 24 randomly selected patients starting treatment, the proportion of time with therapeutic values was 54.2% and 66.9% the first and second months of treatment, respectively.

CONCLUSIONS

Chronic atrial fibrillation is common among the elderly in primary health care, and about half of these patients are treated with warfarin. It appears to be under-diagnosed, and may also be under-treated. About two thirds of treatment time is spent within the therapeutic range, and further improvement of the quality of anticoagulation control with warfarin may therefore be hard to achieve.

Selecting the best heart valve for your patient: mechanical or tissue

This review provides general guidance for heart valve selection. Mechanical heart valves exhibit excellent durability and hemodynamic performance but require anticoagulation to reduce thromboembolism, and therefore risk of anticoagulation-related hemorrhage is increased. Tissue valves were introduced to avoid anticoagulation, but in fact often do not, and lack durability. A literature review was performed to compare the complications of thromboembolism, anticoagulation-related hemorrhage, reoperation structural valve deterioration, and reoperative mortality associated with mechanical and tissue valves. The thromboembolism rates for mechanical and tissue valves are equivalent. During their lives, many recipients of tissue valves receive anticoagulation therapy due to comorbid conditions. The anticoagulation-related blood loss rates associated with mitral mechanical valves and mitral tissue valves are equivalent, whereas the blood loss rates associated with aortic tissue valves are less than those associated with aortic mechanical valves.

Warfarin dose reduction vs watchful waiting for mild elevations in the international normalized ratio

BACKGROUND

Whether clinicians should decrease the warfarin dose in response to a mild, asymptomatic elevation in the international normalized ratio (INR) is unknown.

OBJECTIVES

The study objectives were as follows: (1) to evaluate the safety of an anticoagulation service (ACS) policy advocating that the warfarin dose not be changed for isolated, asymptomatic INRs of < or = 3.4; (2) to compare the dosing strategies of an ACS and primary care providers (PCPs); and (3) to quantify the relationship between reduction of the warfarin dose and the subsequent fall in the INR.

DESIGN AND SETTING

Randomized controlled study of health maintenance organization outpatients who were receiving warfarin.

PATIENTS

We identified 231 patients with a target INR of 2.5 and an isolated, asymptomatic INR between 3.2 and 3.4. Our ACS monitored 103 of the patients; PCPs monitored the remaining 128 patients.

MEASUREMENTS

From all 231 patients, we obtained INRs and warfarin dosing history. From the 103 ACS enrollees, we also recorded adverse events.

RESULTS

One ACS patient had epistaxis in the 30 days after the elevated INR. Twenty-three percent of ACS enrollees and 47% of PCP patients reduced their warfarin dose (p < 0.001). The median follow-up INRs were similar in both cohorts: 2.7 in the ACS enrollees and 2.6 in the PCP patients. However, in a subgroup analysis of 190 patients who presented with an INR of 3.2 or 3.3, ACS enrollees were more likely to have a follow-up INR in the range of 2 to 3 (p = 0.03). The median follow-up INR was 2.7 in 148 patients who maintained their warfarin dose, 2.5 in 77 patients who decreased their dose by 1 to 20%, and 1.7 in 6 patients who decreased their dose by 21 to 43% (p < 0.001).

CONCLUSIONS

These findings support maintaining the same warfarin dose in asymptomatic patients with an INR of < or = 3.3, and reducing the dose for patients who have a greater INR or an increased risk of hemorrhage. Warfarin dose reductions > 20% should be avoided for mildly elevated INRs.

Which approach to anticoagulation management is best? Illustration of an interactive mathematical model to support informed decision making

BACKGROUND

Among patients with atrial fibrillation or mechanical heart valves, determining the best approach to oral anticoagulation largely depends on comparing the costs of anticoagulation management with the costs of events (thromboembolism and bleeding) averted. The Anticoagulation Management Event/Cost Model (ACME) is an interactive mathematical model intended to help clarify these trade-offs.

METHODS

The ACME is a series of linked, nested spreadsheets. At the least detailed level, the user specifies the percentage of patients falling into various management strategies (no anticoagulation, usual physician care, anticoagulation service, patient self-testing/self-management), and the ACME estimates event rates and costs. At more detailed levels the ACME performs a series of weighted average calculations combining, for example, utilization times unit price. Cost categories are divided into event-related and management-related costs (costs of management, testing, and medication).

RESULTS

Regardless of how anticoagulation is subsequently managed, perhaps the greatest benefit is obtained by moving patients who are not currently receiving anticoagulation onto warfarin. Additional benefits can be obtained by eliminating outliers (extremely high or extremely low anticoagulation levels). If changing to a more intensive approach also serves to reduce the tendency for physicians to prescribe anticoagulate below the optimal range, additional savings can be anticipated. The cost calculation typically involves a trade-off between increased up-front costs of anticoagulation management versus greater down-line savings associated with a decreased number of events. To assess the quality of anticoagulation within a given organization, it is critical to know the distribution of clotting levels for the population under anticoagulation.

CONCLUSIONS

Interactive mathematical models, if sufficiently well documented, can be helpful in clarifying decisions regarding costs and benefits of various methods of anticoagulation.

Patient self-management of oral anticoagulation

Patient self-management of oral anticoagulation is now widely practised in Germany and the USA. There are three different home-testing monitors available in the UK which are all reliable in terms of accuracy and reproducibility of results. Selected patients can be trained to perform their own International Normalized Ratio (INR) testing and dosing, with outcomes as good if not better than those from specialized anticoagulant clinics. Consensus on the frequency of testing and what quality control should be deployed is lacking. The cost-effectiveness in the UK is unproven.

Improving the quality of anticoagulation of patients with atrial fibrillation in managed care organizations: results of the managing anticoagulation services trial

Randomized trials have indicated that well-managed anticoagulation with warfarin could prevent more than half of the strokes related to atrial fibrillation. However, many patients with atrial fibrillation who are eligible for this therapy either do not receive it or are not maintained within an optimal prothrombin time-international normalized ratio (INR) range. We sought to determine whether an anticoagulation service within a managed care organization would be a feasible alternative for providing anticoagulation care. We performed a multi-site randomized trial in six large managed care organizations in the United States. Subjects were aged 65 years or older and had nonvalvular atrial fibrillation. At each site, physician practices were divided into two geographically defined practice clusters; each site was randomly assigned to have one intervention and one control cluster. The intervention cluster received an anticoagulation service that satisfied specifications for high-quality anticoagulation care and was coordinated through the managed care organization. Control clusters continued with their usual provider-based care. We measured the proportion of time that warfarin-treated patients in each of the clusters (intervention and control) were in the target range for the INR at baseline, and again during a follow-up period. Five of the six selected sites succeeded at developing an anticoagulation service. Patients in the intervention and control clusters had similar demographic characteristics, contraindications to warfarin, and risk factors for stroke. Among patients (n = 144 in the intervention clusters; n = 118 in the control clusters) for whom data were available during the baseline and follow-up periods, the changes in percentages of time in the target range were similar for those in the intervention clusters (baseline: 47.7%; follow-up: 55.6%) and in the control clusters (baseline: 49.1%; follow-up: 52.3%; intervention effect: 5%; 95% confidence interval: -5% to 14%; P = 0.32). Although it was feasible in a managed care organization to implement anticoagulation services that were tailored to local circumstances, provision of this service did not improve anticoagulation care compared with usual care. The effect of the anticoagulation service was limited by the utilization of the service, the degree to which the referring physician supports strict adherence to recommended target ranges for the INR, and the ability of the anticoagulation service to identify and to respond to out-of-range values promptly.

Better anticoagulation control improves survival after valve replacement

OBJECTIVE

We sought to assess the effect of anticoagulation control on long-term survival after valve replacement with the Medtronic Hall valve (Medtronic, Inc, Minneapolis, Minn).

METHODS

Prospective follow-up data, including 82,297 international normalized ratios, were collected for 1476 patients undergoing single valve replacement with the Medtronic Hall valve between 1979 and 1994, with follow-up to the end of 1998. After excluding 204 patients who either died within 30 days or had fewer than 10 international normalized ratios recorded beyond 30 days, there were 10,203 patient years of follow-up for analysis. Anticoagulation variability was measured as the percentage of international normalized ratios outside a target range of 2.0 to 4.0 for each patient.

RESULTS

Linearized rates for late death rose progressively with increasing deciles of anticoagulation variability for both aortic and mitral valve replacement (2.7% and 3.3% per year, respectively, in deciles 1 and 2 up to 9.5% and 14.6% per year, respectively, in deciles 6-10; P <.001). Survival at 15 years after aortic valve replacement was 59% for low anticoagulation variability (deciles 1 and 2), 55% for intermediate anticoagulation variability (decile 3), and 28% for high anticoagulation variability (deciles 4-10); survivals at 15 years after mitral valve replacement were 56%, 42%, and 24%, respectively (P <.001 between low-intermediate anticoagulation variability and high anticoagulation variability for both aortic and mitral valve replacement). On multivariate analysis, significant predictors of reduced survival were anticoagulation variability per 20% increase (hazard ratio, 1.8), diabetes (hazard ratio, 1.6), decade of age (hazard ratio, 1.6), concomitant coronary artery bypass grafting (hazard ratio, 1.5), male sex (hazard ratio, 1.4), hypertension (hazard ratio, 1.4), New York Heart Association class III or IV (hazard ratio, 1.3), and non-sinus rhythm (hazard ratio, 1.2). Patients with low anticoagulation variability who were in sinus rhythm and did not have diabetes, coronary bypass grafting, or hypertension had survivals equal to those of the age- and sex-matched general population at 15 years. The incidence of valve-related deaths was significantly higher with high anticoagulation variability compared with the incidence with low-intermediate anticoagulation variability for both aortic (1.4% vs 0.5% per year, P <.001) and mitral valve replacement (1.5% vs 0.5% per year, P <.001). By means of univariate analysis, high anticoagulation variability was significantly associated with New York Heart Association class III or IV at 5 years postoperatively (P <.001) and with age of greater than 60 years at the time of the operation (P =.002).

CONCLUSIONS

High anticoagulation variability is the most important independent predictor of reduced survival after valve replacement with a mechanical valve. Better anticoagulation control should improve survival.