Personal experiences of self-monitoring >

Five years of self-management

John Kelman

John has kindly provided us with graphs of his records. You can see them by clicking the red links in his article.

After major surgery, it is obviously important to recover from the surgery itself. However, for many people it is just as important for to be able to pick up and continue life as close as possible to what it was before and for many people this is possible apart from one exception - oral anticoagulant treatment.

Oral anticoagulation treatment with warfarin (a vitamin-K antagonist) is essential after valve replacement surgery, especially with mechanical prosthesis to avoid thrombus formation (clots) but at the same time to ensure a level to prevent haemorrhagic (bleeding) complications. Prevention of under-dosing and over-dosing with warfarin requires constant laboratory measurement of blood prothrombin time, which is expressed as International Normalised Ratio (INR). The management of anticoagulant treatment normally involves a hospital-based anticoagulation clinic, or by the general practitioner. Both methods require a person's availability to attend regular sessions every two or three weeks for a venous blood sample. This can be very difficult for people who work, especially in the modern working environment.

There are currently available in the UK two compact, lightweight portable instruments to facilitate prothrombin time measurement (expressed as INR) using a drop of capillary blood. The CoaguChek S from Roche Diagnostics and the Hemosense INRatio from Sysmex are tools used to measure INR as part of an oral anticoagulation self-management programme.

I was forty years old when I was diagnosed with a prolapsed mitral valve that had been present since birth. I had mitral valve replacement surgery in April 2000 and have self-managed anticoagulant treatment since June 2000.

Self-management of anticoagulant treatment was actively promoted by my surgeon Mr I M Mitchell of Nottingham City Hospital at the time of my post-operation recovery in hospital. I was very determined and was fit enough to go back to work twelve weeks after the operation. My work requires flexibility and mobility and therefore I could not be restricted to making regular visits to an anticoagulant clinic. Initially, my local anticoagulant clinic (Queen's Medical Centre, Nottingham) was responsible for getting my anticoagulant treatment started and to provide training on how to use the CoaguChek S instrument for self-management.

From the start of anticoagulant treatment it is clear that warfarin constantly interacts with an individual's diet, medication and lifestyle. Changes in these interactions with warfarin can increase or decrease INR so for an individual's anticoagulant treatment to be a success, accurate record keeping is very much a necessity. It is important that a person knows exactly how much warfarin is being taken every day. A comprehensive set of records also enables a person to develop an organised anticoagulant treatment plan. Table 1 is an example of a daily data table recording INR test results, daily warfarin dosage in number of tablets, daily warfarin dosage in milligrams (i.e. 3 blue tablets = 9.0 mg) and average daily warfarin dosage (average per day over number of days, usually the period between INR tests).

INR test and warfarin data can also be organised in a format that is shown in Table 2. The data that is entered from each INR test can now be used to calculate a parameter called the 'moving average'. This parameter is highlighted in yellow and a sample calculation for a given six-week moving average figure is shown. The six-week moving average of INR test data will allow a person to look back over the short term and plan forward more effectively. Presenting the data from Table 2 in a graphical format is an instructive way to represent INR test results, average daily warfarin dosage and the moving average data. An example of anticoagulant test data from April 2004 to April 2005 is plotted in Figure 1. This plot can easily show the variations in daily dosage and INR test data over an extended period of time and is a valuable tool in the self-management of an anticoagulant treatment plan.

The quality of INR data that is acquired from blood testing is dependent on the frequency of testing. This frequency and data quality is only available to people who can self-manage their anticoagulant treatment. Theoretically self-management allows a person to perform an INR test every day. This is obviously an extreme example, however it can be pointed out that at various times it can be necessary as well as useful to perform extra INR tests as warfarin interactions with a person's lifestyle is variable throughout a lifetime of treatment. Only self-management can be flexible and practical enough to allow a person to perform an INR blood test at any time.

Data accumulated from June 2000 to April 2005 contains 263 INR tests which is equal to a frequency of one test per week. Of the 263 INR tests recorded 227 of these tests were within a therapeutic range of 2.50 to 3.50. This is an 86.3% success rate over five years. This is a direct result of frequency of testing. These results are actually better over the last four years April 2001 to April 2005 and are 90% within range. This is because in the first six months of anticoagulant treatment a person's interaction with warfarin is extremely variable as the body becomes adjusted to warfarin in the bloodstream. Table 3 summarises the INR test data during the period and plots the annual percentage of tests within therapeutic range.

Accumulated INR test and warfarin data is also presented in a plot (Figure 2) with the six-week moving average curve and average daily warfarin curve. This plot shows a variable warfarin dosage pattern very clearly. Differences in a person's interaction with warfarin (black curve with warfarin scale on right axis) is highlighted over the specific time period. This plot also highlights the importance of the six-week moving average parameter (red curve with INR scale on the left axis). Although this curve fluctuates as long as it remains within the therapeutic INR range of 2.50 to 3.50 then I believe that a person's anticoagulant treatment is a success. Clearly in this example the moving average curve remains within the required range at least 95% of the time over the period. Only self-management can deliver the required frequency of INR testing that is necessary to achieve this sort of result.

During anticoagulant treatment it is important to identify patterns of INR testing or warfarin dosing that might be related to a person's life environment. An example of this is shown in Figure 3 because it plots annual six-week moving average curves (red) as well as average daily dosage curves (black) with each year overlapping. In this example it appears that from mid-June to August and mid-January to March every year INR testing becomes similar and seem related while mid-August to October shows more fluctuation from year to year. The cause is unknown and the data only relates to myself but it could be as simple as summer light and diet and the lengthening days from January to March. What it does reinforce is the need to take a person's lifestyle and environment into account when managing anticoagulant treatment.

During the period June 2000 to April 2005, 5,482.5 blue warfarin tablets each of 3mg have been taken (Table 3). Figure 4 shows that 53.3% were a daily dose of three tablets. Figure 4 also shows that 95% of all tablets taken were either 2.5, 3 or 3.5 per day.

The ability to check INR more frequently by self-testing is successful in achieving INR target range levels. From this understanding, management of oral anticoagulation can be achieved with a significant degree of accuracy. This in turn reduces the risk of thromboembolic (clotting) or haemorrhagic (bleeding) events. The data presented demonstrates that self-management of anticoagulant treatment is feasible for significant numbers of people and constitutes a significant service improvement when compared with conventional management of treatment. However, I believe that you have to be prepared to record and use the data in the way that the various examples outline in this article. You do not need a computer to do this properly. All that is required is a book to record data and some graph paper to plot the data. It has to be emphasised that the ability to self-manage effectively is linked to the quality of information gathered during an extended period of time. It becomes clear that frequency of testing is key to a successful treatment because of the way that warfarin interacts directly with a person's environment, lifestyle and diet. Self-management can deliver a much higher frequency of testing. It is only from frequent INR testing that accurate regulation of daily warfarin can be achieved. Only self-management can incorporate variables such as diet, lifestyle and environment into an anticoagulant treatment plan.

Therefore people can be totally self-sufficient and can manage anticoagulant treatment safely, accurately and frequently thus avoiding the inconvenience and added costs of attending regular anticoagulation clinics.