Response to Letter by Dangayach and Panchabhai
We highly appreciate Dr Dangayach’s interest in our article concerning the use of a point-of-care international normalized ratio (INR) testing device (PoC) accelerating thrombolysis in acute ischemic stroke patients on oral anticoagulants.1 Indeed, the precision of PoC devices may differ between manufacturers, therefore the reliability of each PoC device should be evaluated locally before using it in acute stroke care. In addition, quality control should be performed regularly.
Drs Dangayach and Panchabhai raise another important point regarding the usefulness of PoC INR coagulometers in the setting of stroke prevention. Self-monitoring of the INR is a reliable method to assure adequate anticoagulation in patients on vitamin K antagonists.2 A significant number of patients with atrial fibrillation who receive long-term oral anticoagulation are outside the therapeutic target range.3,4 Presumably, this decreases the protective effect of vitamin K antagonists and increases the risk of hemorrhagic complications, respectively.5,6 Although it is plausible that frequent PoC-guided INR self-testing increases the patients’ time within the target INR range, the efficacy of PoC-guided INR monitoring has not been tested in a large prospective controlled trial in stroke-prone patients experiencing atrial fibrillation to our knowledge.
Our study was a monocenter pilot study. Although in some hospitals, the time gain of PoC INR measurements may be negligible, in many medical centers, availability of central laboratory INR will be even more delayed. An important advantage of PoC INR measurements is the instant availability of the INR in the emergency room, which is useful for guidance of medical or interventional recanalization therapy in stroke patients on oral anticoagulation. In addition to the reported usefulness in acute ischemic stroke patients, PoC can also be used in the reversal treatment of patients with OAC-related intracerebral hemorrhages.7
Sources of Funding
R.V. is supported by an Else-Kröner Memorial Scholarship.
Rizos T, Herweh C, Jenetzky E, Lichy C, Ringleb PA, Hacke W, Veltkamp R. Point-of-care international normalized ratio testing accelerates thrombolysis in patients with acute ischemic stroke using oral anticoagulants. Stroke. 2009; 40: 3547–3551.
Ansell J, Jacobson A, Levy J, Voller H, Hasenkam JM. 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. Int J Cardiol. 2005; 99: 37–45.
Jones M, McEwan P, Morgan CL, Peters JR, Goodfellow J, Currie CJ. Evaluation of the pattern of treatment, level of anticoagulation control, and outcome of treatment with warfarin in patients with non-valvar atrial fibrillation: a record linkage study in a large British population. Heart. 2005; 91: 472–477.
Connolly SJ, Pogue J, Eikelboom J, Flaker G, Commerford P, Franzosi MG, Healey JS, Yusuf S. Benefit of oral anticoagulant over antiplatelet therapy in atrial fibrillation depends on the quality of international normalized ratio control achieved by centers and countries as measured by time in therapeutic range. Circulation. 2008; 118: 2029–2037.
Rizos T, Jenetzky E, Herweh C, Hug A, Hacke W, Steiner T, Veltkamp R. Point-of-care reversal treatment in warfarin-related intracerebral hemorrhage. Ann Neurol. Published online ahead of print on January 12, 2010. DOI: 10.1002/ana.21965.