To cite this article: Ryan F, Byrne S, OÕShea S. Randomized controlled trial of supervised patient self-testing of warfarin therapy using an internetbased expert system. J Thromb Haemost 2009; 7: 1284-90.Summary. Background: Increased frequency of prothrombin time testing, facilitated by patient self-testing (PST) of the International Normalized Ratio (INR) can improve the clinical outcomes of oral anticoagulation therapy (OAT). However, oversight of this type of management is often difficult and timeconsuming for healthcare professionals. This study reports the first randomized controlled trial of an automated direct-topatient expert system, enabling remote and effective management of patients on OAT. Methods: A prospective, randomized controlled cross-over study was performed to test the hypothesis that supervised PST using an internet-based, direct-topatient expert system could provide improved anticoagulation control as compared with that provided by an anticoagulation management service (AMS). During the 6 months of supervised PST, patients measured their INR at home using a portable meter and entered this result, along with other information, onto the internet web page. Patients received instant feedback from the system as to what dose to take and when the next test was due. During the routine care arm, patients attended the AMS at least every 4-6 weeks and were dosed by the anticoagulation pharmacist or physician. The primary outcome variable was the difference in the time in therapeutic range (TTR) between both arms. Results: One hundred and sixty-two patients were enrolled (male 61.6%, mean age 58.7 years), and 132 patients (81.5%) completed both arms. TTR was significantly higher during PST management than during AMS management (median TTR 74% vs 58.6%; z=5.67, P < 0.001). Conclusions: The use of an internet-based, direct-to-patient expert system for the management of PST improves the control of OAT as compared with AMS management.
Improved anticoagulation control results in improved outcomes, with a decrease in the incidence of bleeding and thromboembolic events. The outcomes of oral anticoagulation therapy (OAT) are dependent on the model of care used to manage warfarin therapy, with better outcomes associated with the use of a specialised anticoagulation management service (AMS), computerized decision support and increased testing frequency (facilitated by patient self-testing (PST) of the international normalised ratio (INR)) (Ansell and Hughes 1996). This study uses a novel strategy to combine the advantages of these three approaches to warfarin management. A prospective, randomized controlled cross-over study was carried out at the anticoagulation clinic of Cork University Hospital, Ireland, to test the hypothesis that supervised PST using an internet based expert system could provide comparable anticoagulation control to that provided by traditional outpatient AMS management. This was a cross-over study; patients served in both AMS and supervised PST arms, with random assignment as to the order of management. Both arms were six months in duration. Patients on established long term OAT who had internet access were eligible for enrolment. During the supervised PST arm of the study, patients measured their INR at home using the CoaguChek XS® point of care meter, (Roche Diagnostics, UK) either twice weekly, weekly or every two weeks depending on their anticoagulation control. They entered this result along with other information relating to their warfarin therapy (e.g. signs or symptoms of thrombosis or hemorrhage, missed doses, concurrent illnesses, dietary or medication changes etc) onto the CoagCare® (Zycare Inc, Chapel Hill, NC) web page. Patients with a therapeutic INR and no other issues were automatically provided with algorithm-derived dosing and repeat testing instructions. Patients with non-therapeutic results, or symptoms suggestive of thromboembolic or hemorrhagic complications, were prioritized for caregiver review according to problem severity. During the AMS arm, patients were required to attend the clinic every four to six weeks, or more frequently, if clinically indicated. Dosage adjustments were performed by the anticoagulant clinic staff using the laboratory INR and the APEX® (iSOFT, UK) computer decision support software. The primary outcome variable to assess anticoagulation control was the difference in time in therapeutic range (TTR) during the AMS management and supervised PST management period. In addition, the number of INR measurements indicative of serious under- or over-anticoagulation and the number of serious hemorrhagic or thrombotic adverse events were also compared. One hundred and sixty two patients were enrolled over a nine-month period (July 2006–April 2007). The majority of study patients were male (61.4%) and the mean age of the study population was 59.6 +/−14.3 years. One hundred and thirty two (81.5%) patients completed both arms of the study. The mean TTR during the AMS arm was 60.2% +/−19.5%, which increased to 71.4% +/− 13.6% during the PST period (p<0.001). Eighty-seven patients (65.91%) achieved better anticoagulation control during the supervised PST period. Patients measured their INR almost four times more frequently while home-testing giving a mean frequency of INR testing of 4.5 days compared with 17.4 days for the AMS period. Extreme INR values (< 1.5 and > 5.0) occurred more frequently during the AMS arm of the study (6% vs 2.4%, p<0.001). There was no significant difference in the adverse event rate between the two study periods. Table 1. Table 1. Adverse events Model of care Hemorrhagic Thromboembolic AMS Gastric bleed (INR 2.5) TIA (INR 2.2) Supervised PST None DVT (INR 1.6) DVT (1.4) Daily time to manage 70 patients ranged from 10 to 45 minutes (mean 23.19+/−9.48 mins/day). This novel system of supervised PST using an internet based expert system improves the clinical effectiveness of OAT when compared with management by a specialized anticoagulant management service.
The development of point-of-care (POC) testing devices enables patients to test their own international normalized ratio (INR) at home. However, previous studies have shown that when compared with clinical laboratory values, statistically significant differences may occur between the two methods of INR measurement. The aim of this study was to evaluate the accuracy of the CoaguChek S and XS POC meters relative to clinical laboratory measurements. As part of a randomized, crossover patient self-testing (PST) study at Cork University Hospital, patients were randomized to 6 months PST or 6 months routine care by the anticoagulation management service. During the PST arm of the study, patients measured their INR at home using the CoaguChek S or XS POC meter. External quality control was performed at enrollment, 2 months and 4 months by comparing the POC measured INR with the laboratory determined value. One hundred and fifty-one patients provided 673 paired samples. Good correlation was shown between the two methods of determination (r = 0.91), however, statistically significant differences did occur. A Bland-Altman plot illustrated good agreement of INR values between 2.0 and 3.5 INR units but there was increasing disagreement as the INR rose above 3.5. Eighty-seven per cent of all dual measurements were within the recommended 0.5 INR units of each other. This study adds to the growing evidence that POC testing is a reliable and safe alternative to hospital laboratory monitoring but highlights the importance of external quality control when these devices are used for monitoring oral anticoagulation.
Summary Many physicians are reluctant to prescribe oral anticoagulation therapy (OAT) because of the fear of haemorrhagic complications. Changes in patient health, lifestyle or diet and other drugs can alter the effectiveness of oral anticoagulants. These potential interferences, added to the fact that each individual has a different reaction to these drugs, requires that therapy is monitored regularly. This article aims to review those strategies which help to achieve optimal anticoagulation control and improve the outcomes of OAT. Relevant articles were identified through a search of MEDLINE and included publications reporting on intensity of anticoagulation, the initiation of therapy and the role of pharmacogenetics, the transition from primary to secondary care, management by specialized clinics using decision support software and home‐testing. Implementation of these strategies would increase the use of oral anticoagulants by physicians and offers the potential to improve patient safety and reduce adverse events.
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