The clinical evaluation of International Normalized Ratio variability and control in conventional oral anticoagulant administration by use of the variance growth rate. Issue 8 (14th August 2013)

• Record Type: Journal Article
• Authors: Ibrahim, S.; Jespersen, J.; Poller, L.
• Is Part Of: Journal of thrombosis and haemostasis. Volume 11:Issue 8(2013)
• Page Start: 1540
• Page End: 1546
• Publication Date: 2013-08-14
• Subjects: Thrombosis -- Periodicals; Hemostasis -- Periodicals; Blood coagulation disorders -- Periodicals; 616.1
• DOI: 10.1111/jth.12322
• Languages: English
• ISSNs: 1538-7933

Abstract

<abstract abstract-type="main" id="jth12322-abs-0001"> <title>Summary</title> <sec id="jth12322-sec-0001" sec-type="section"> <title>Introduction</title> <p>The time in target International Normalized Ratio (INR) range (TIR) is used to assess the control and intensity of oral anticoagulation, but it does not measure variation in the INR.</p> </sec> <sec id="jth12322-sec-0002" sec-type="section"> <title>Objectives</title> <p>The value of assessing INR variability by use of the variance growth rate (VGR) as a predictor of events was investigated in patients treated with warfarin.</p> </sec> <sec id="jth12322-sec-0003" sec-type="section"> <title>Methods</title> <p>Three different methods of VGR determination (A, B1, and B2) together with the TIR were studied. Method A measures both INR variability and control, but methods B1 and B2 measure variability only. The VGR and TIR were determined over three time periods: overall follow‐up to an event, and 6 months and 3 months before an event.</p> </sec> <sec id="jth12322-sec-0004" sec-type="section"> <title>Results</title> <p>Six hundred and sixty‐one control patients were matched to 158 cases (bleeding, thromboembolism, or death). With all VGR methods, the risk of an event was greater in unstable patients at 6 months before an event than in stable patients. Method A demonstrated the greatest risk 3 months before an event in the unstable VGR group as compared with the stable group (odds ratio 3.3, 95% confidence interval 1.9–5.7, <italic>P </italic>< 0.005). The risk of an event was 1.9 times greater in patients with a low TIR (< 39%) than in those with a high TIR (> 80%) in the 3‐month period (<italic>P </italic>= 0.02). Risk of bleeding was significantly greater in the 3‐month period in patients with unstable VGR, with the greatest risk found with method B2 (<italic>P </italic>< 0.01).</p> </sec> <sec id="jth12322-sec-0005" sec-type="section"> <title>Conclusions</title> <p>Patients with unstable anticoagulation have a significantly increased risk of 'clinical events' at 3 and 6 months before an event. The VGR can be incorporated into computer‐dosage programs, and may offer additional safety when oral anticoagulation is monitored.</p> </sec> </abstract>