- Email: [email protected]
Self-management of oral anticoagulation
CORRESPONDENCE
COMMENTARY
CORRESPONDENCE Self-management of oral anticoagulation Sir—Manon Cromheecke and colleagues’ study (July 8, p 97)1 purports to be a randomised crossover study, but had serious flaws in the methods and the results warrant discussion. Despite the stated sample size, the numbers are too small for meaningful conclusion. To detect a difference in therapeutic control at the levels stated, at least 250 patients would be required. The role of education has been glossed over by the crossover design. The possibility of bias in either control group is not, however, excluded because the first control group had presumably not received any education and the second control group would have received education some time before reverting to routine care. Despite these concerns, the real issue surrounds the interpretation of the results. The routinely managed group were tested every 9 days and achieved poor therapeutic control, with only 60% of patients being within range more than 50% of the time. This finding reflects suboptimum care compared with routine UK data and does not justify the need for such frequent testing.2,3 In comparison, the self-managed group did testing slightly more frequently and had slightly better results. Cromheecke and colleagues chose an unusual measure of therapeutic control, namely the proportion of patients in range for a percentage of time. It would be interesting to see the results using standard measures, such as the number of tests in a range, point prevalence, or mean percentage time in range. We contest Cromheecke and colleagues’ assertion that specialised anticoagulation clinics result in better control of anticoagulation than control in general practice. Neither reference provided to support this statement is relevant and several studies show the opposite.4,5 We did a similar small-scale study in the UK and showed that self-managed and control (primary-care managed) populations achieved therapeutic international normalised ratios more than 70% of the time despite the selfmanaged patients testing themselves
THE LANCET • Vol 356 • October 21, 2000
three times as often. Cromheecke and colleagues’ data are supported by German data, therefore, more research is required in the UK before this model of care can be seen to replace routine management. It is not clear why the European data compare so poorly with the UK data, but it is clear to us that the intensity of testing suggested is too frequent and gives no benefit over and above routine management observed in the UK. *D A Fitzmaurice, E T Murray, F D R Hobbs The Medical School, Edgbaston, Birmingham B15 2TT, UK 1
2 3
4
5
Cromheecke ME, Levi M, Colly LP, et al. Oral anticoagulation self-management and management by a specialist anticoagulation clinic: a randomised cross-over comparison. Lancet 2000; 356: 97–102. Rose PE. Audit of anticoagulant therapy. J Clin Pathol 1996; 49: 5–9. Fitzmaurice DA, Hobbs FDR, Murray ET. Primary care anticoagulant clinic management using computerized decision support and near patient International Normalized Ratio (INR) testing: routine data from a practice nurse-led clinic. Family Pract 1998; 15: 144–46. Pell JP, McIver B, Stuart P, Malone DNS, Alcock J. Comparison of anti-coagulant control among patients attending general practice and a hospital anti-coagulant clinic. Br J Gen Pract 1993; 43: 152–54. Fitzmaurice DA, Hobbs FDR, Murray ET, Bradley CP, Holder RL. Evaluation of computerized decision support for oral anticoagulation management based in primary care. Br J Gen Pract 1996; 46: 533–55.
Authors’ reply Sir—D A Fitzmaurice and E T Murray criticise our sample size as being too small for a meaningful conclusion. They do not, however, substantiate this criticism, whereas we described extensively the sample-size motivation with all the appropriate assumptions. Second, Fitzmaurice and Murray suggest that bias may have been present in the control groups because of a difference in the timing of education. They have overlooked that we state that all participants were educated before randomisation to either treatment strategy. In addition, we clearly report that the order of management strategies in the study did not affect any of the outcome factors.
Many patients were not in the therapeutic range for much of the time during both management strategies, but we contest that this finding represents a suboptimum care compared with routine UK data. Our results are in agreement with almost all major clinical studies on the use of oral anticoagulant therapy, including those of patients from the UK.1 Interestingly, the published data from Fitzmaurice and Hobbs that they reference show even less control of anticoagulation, with only 53·4% of the measurements in the therapeutic range, which does not support their claim of better control of anticoagulation in their patients. We disagree with Fitzmaurice and Hobbs that our references do not support the statement on better control of anticoagulation in clinics than in general practice. S Cortelazzo and colleagues convincingly show a reduction in bleeding complications and thrombotic events in patients with mechanical heart valves during management by an anticoagulation clinic compared with routine practice.2 J P Pell and co-workers show that UK general practice is a minimum of 7% better than hospital-based anticoagulation clinics, but general practice patients were checked almost three times more than those at clinics, whereas the referenced study by D A Fitzmaurice and colleagues does not address this issue. Our statement agrees with the consensus conference on antithrombotic therapy of the American College of Chest Physicians. We believe that self-management of anticoagulation is a valuable adjunct in the management of patients requiring anticoagulant therapy. *Marcel Levi, Harry Büller Departments of *Internal Medicine and Vascular Medicine, Academic Medical Centre, University of Amsterdam, Netherlands (e-mail: [email protected]) 1
2
Poller L, Shiach CR, MacCallum PK, et al. Multicentre randomised study of computerised anticoagulant dosage. European Concerted Action on Anticoagulation. Lancet 1998; 352: 1505–09. Cortelazzo S, Finazzi G, Viero P, et al. Thrombotic and hemorrhagic complications in patients with mechanical heart valve prosthesis attending an anticoagulation clinic. Thromb Haemost 1993; 69: 316–20.
1437
For personal use only. Not to be reproduced without permission of The Lancet.
COMMENTARY
CORRESPONDENCE Self-management of oral anticoagulation Sir—Manon Cromheecke and colleagues’ study (July 8, p 97)1 purports to be a randomised crossover study, but had serious flaws in the methods and the results warrant discussion. Despite the stated sample size, the numbers are too small for meaningful conclusion. To detect a difference in therapeutic control at the levels stated, at least 250 patients would be required. The role of education has been glossed over by the crossover design. The possibility of bias in either control group is not, however, excluded because the first control group had presumably not received any education and the second control group would have received education some time before reverting to routine care. Despite these concerns, the real issue surrounds the interpretation of the results. The routinely managed group were tested every 9 days and achieved poor therapeutic control, with only 60% of patients being within range more than 50% of the time. This finding reflects suboptimum care compared with routine UK data and does not justify the need for such frequent testing.2,3 In comparison, the self-managed group did testing slightly more frequently and had slightly better results. Cromheecke and colleagues chose an unusual measure of therapeutic control, namely the proportion of patients in range for a percentage of time. It would be interesting to see the results using standard measures, such as the number of tests in a range, point prevalence, or mean percentage time in range. We contest Cromheecke and colleagues’ assertion that specialised anticoagulation clinics result in better control of anticoagulation than control in general practice. Neither reference provided to support this statement is relevant and several studies show the opposite.4,5 We did a similar small-scale study in the UK and showed that self-managed and control (primary-care managed) populations achieved therapeutic international normalised ratios more than 70% of the time despite the selfmanaged patients testing themselves
THE LANCET • Vol 356 • October 21, 2000
three times as often. Cromheecke and colleagues’ data are supported by German data, therefore, more research is required in the UK before this model of care can be seen to replace routine management. It is not clear why the European data compare so poorly with the UK data, but it is clear to us that the intensity of testing suggested is too frequent and gives no benefit over and above routine management observed in the UK. *D A Fitzmaurice, E T Murray, F D R Hobbs The Medical School, Edgbaston, Birmingham B15 2TT, UK 1
2 3
4
5
Cromheecke ME, Levi M, Colly LP, et al. Oral anticoagulation self-management and management by a specialist anticoagulation clinic: a randomised cross-over comparison. Lancet 2000; 356: 97–102. Rose PE. Audit of anticoagulant therapy. J Clin Pathol 1996; 49: 5–9. Fitzmaurice DA, Hobbs FDR, Murray ET. Primary care anticoagulant clinic management using computerized decision support and near patient International Normalized Ratio (INR) testing: routine data from a practice nurse-led clinic. Family Pract 1998; 15: 144–46. Pell JP, McIver B, Stuart P, Malone DNS, Alcock J. Comparison of anti-coagulant control among patients attending general practice and a hospital anti-coagulant clinic. Br J Gen Pract 1993; 43: 152–54. Fitzmaurice DA, Hobbs FDR, Murray ET, Bradley CP, Holder RL. Evaluation of computerized decision support for oral anticoagulation management based in primary care. Br J Gen Pract 1996; 46: 533–55.
Authors’ reply Sir—D A Fitzmaurice and E T Murray criticise our sample size as being too small for a meaningful conclusion. They do not, however, substantiate this criticism, whereas we described extensively the sample-size motivation with all the appropriate assumptions. Second, Fitzmaurice and Murray suggest that bias may have been present in the control groups because of a difference in the timing of education. They have overlooked that we state that all participants were educated before randomisation to either treatment strategy. In addition, we clearly report that the order of management strategies in the study did not affect any of the outcome factors.
Many patients were not in the therapeutic range for much of the time during both management strategies, but we contest that this finding represents a suboptimum care compared with routine UK data. Our results are in agreement with almost all major clinical studies on the use of oral anticoagulant therapy, including those of patients from the UK.1 Interestingly, the published data from Fitzmaurice and Hobbs that they reference show even less control of anticoagulation, with only 53·4% of the measurements in the therapeutic range, which does not support their claim of better control of anticoagulation in their patients. We disagree with Fitzmaurice and Hobbs that our references do not support the statement on better control of anticoagulation in clinics than in general practice. S Cortelazzo and colleagues convincingly show a reduction in bleeding complications and thrombotic events in patients with mechanical heart valves during management by an anticoagulation clinic compared with routine practice.2 J P Pell and co-workers show that UK general practice is a minimum of 7% better than hospital-based anticoagulation clinics, but general practice patients were checked almost three times more than those at clinics, whereas the referenced study by D A Fitzmaurice and colleagues does not address this issue. Our statement agrees with the consensus conference on antithrombotic therapy of the American College of Chest Physicians. We believe that self-management of anticoagulation is a valuable adjunct in the management of patients requiring anticoagulant therapy. *Marcel Levi, Harry Büller Departments of *Internal Medicine and Vascular Medicine, Academic Medical Centre, University of Amsterdam, Netherlands (e-mail: [email protected]) 1
2
Poller L, Shiach CR, MacCallum PK, et al. Multicentre randomised study of computerised anticoagulant dosage. European Concerted Action on Anticoagulation. Lancet 1998; 352: 1505–09. Cortelazzo S, Finazzi G, Viero P, et al. Thrombotic and hemorrhagic complications in patients with mechanical heart valve prosthesis attending an anticoagulation clinic. Thromb Haemost 1993; 69: 316–20.
1437
For personal use only. Not to be reproduced without permission of The Lancet.