A total of 23 patients were trained in self-management of warfarin therapy. There was no statistically significant difference in TTR with conventional therapy (70 %) versus self-management (75 %) (Figure 1). However, variation in TTR (Figure 1) and the percentage of INR extreme values (Table 3) were both significantly reduced with self-management compared to conventional therapy. Given the large differences in duration and relatively small number of participants, it is not possible to draw any conclusions about whether conventional therapy and self-management differ with regard to complications.
Our findings concur with the results of meta-analyses, which have shown that TTR during self-management is equal to or greater than that achieved with conventional therapy (12, 15). During self-management, the INR was analysed more frequently than with conventional therapy (Table 3). This means that values outside the therapeutic range are detected more quickly, which probably leads to more rapid adjustment of warfarin dose (14), which in turn increases TTR. Indeed, it has been shown that an increased frequency of INR measurements leads to increased TTR (30, 31). This may explain why the proportion of INR extreme values (Table 3) and the variation in TTR (Figure 1) were lower during self-management than with conventional therapy, in common with previous meta-analyses (13). Increased INR variation has been shown to correlate with an increased incidence of death, stroke and bleeding (32).
An important aspect of self-management is that patients become more knowledgeable about and more involved with their own treatment. This presumably leads to a more positive attitude towards treatment in these patients compared to those who have not received such training. This may also contribute to increased compliance (33).
To verify CoaguChek XS measurements during the training period, blood samples were collected for measurement of the INR using hospital instruments (parallel analysis, Table 2). Organisations including the International Organization for Standardization (34) and the Clinical and Laboratory Standards Institute (35) recommend that patients who self-test should participate in an external quality assurance programme. Among the external quality control organisations in Europe, as yet only «External quality Control of diagnostic Assays and Tests» (ECAT) in the Netherlands offers such a programme for patients who perform INR self-testing (36). Germany has chosen not to offer this service because of a lack of capacity resulting from large patient numbers, and because the control sample material has not been adequate (37). However, new control materials have entered the market, and Noklus is planning a study to test different models of external quality control for self-testing devices. Currently, Noklus recommends that patients have their device checked twice a year at their GP surgery.
A strength of this study is that the same patients underwent both conventional therapy and self-management, thus the patients can act as their own controls. In addition, all enrolled patients completed the entire study. A weakness is that there were relatively few patients compared with large international studies, but nonetheless enough to be able to demonstrate a 10 % change in TTR, as recommended (14). As more Norwegian patients undergo training, more robust data will be obtained.
Patients were selected on the basis that they wished to begin self-management, and were considered suitable for self-management by their GP. This means that the patients in this study are a selected group, and the results are therefore not representative of all patients on anticoagulation treatment. Selection of patients is, however, a recommended and common practice in clinical trials (11) – (13).
Patients provided written feedback after each evening training session and at the end of the study. They were generally very satisfied with the training programme and follow-up (1). On the basis of the evaluations, the training programme was revised and shortened to 21 weeks. This programme is now being used to train patients in ten health authorities in Norway (38, 39), with training paid for by the hospitals. Although direct oral anticoagulants are expected to replace warfarin for a large proportion of patients with atrial fibrillation in the future, warfarin will remain the first choice for many others, including those with an artificial heart valve. If this standardised training programme were implemented in all health authorities, all suitable patients on long-term warfarin therapy could have equal access to self-management irrespective of their geographical location. It is puzzling that the Norwegian government earmarked NOK 87 million for direct oral anticoagulants in 2013 (40), whereas no funds have been allocated to training patients in self-management of warfarin.