Participants were recruited from practices representing a range of socioeconomic diversity, including practices with postcodes in the fifth most deprived and second most affluent areas in Lothian, Scotland. Four hundred and one participants from 20 general practices (range 5-45 participants per practice) were randomly assigned to the monitored (n=200) or usual care (n=201) group (fig 1). Of these, 182 (91%) in the intervention group and 177 (88%) in the usual care group undertook daytime ambulatory blood pressure monitoring for the primary outcome. In total, 195 (98%) in the intervention group and 185 (93%) in the usual care group attended the follow-up visits at six months and provided some data. Of those not providing complete data, 11 participants in the intervention group and eight in the usual care group declined to have repeat ambulatory blood pressure monitoring; three for medical reasons and 16 because they felt the procedure too uncomfortable. Of the remainder, a further six participants in the intervention group and 14 in the usual care group were either lost to follow-up or withdrew consent, and one in the intervention group and two in the usual care group died before follow-up. Around half of the participants in the intervention group asked for text or email alerts at some point, although a small number subsequently asked for them to be switched off.
Fig 1 Flow of participants through trial. ABPM=ambulatory blood pressure monitoring
Table 1 shows the baseline characteristics of the 401 participants and the characteristics of those who did not provide primary outcome data. The trial arms were well balanced.
Table 1 Baseline characteristics for full dataset and for participants not providing primary outcome data. Values are numbers (percentages) unless stated otherwise
The mean daytime systolic ambulatory blood pressure fell in both groups, from 146.0 mm Hg to 140.0 mm Hg in the telemonitoring arm and from 146.5 mm Hg to 144.3 mm Hg in the usual care arm (table 2. The difference between the two arms at six months (that is, usual care minus intervention) was 4.3 mm Hg (95% confidence interval 2.0 to 6.5; P=0.0002), adjusted for baseline mean daytime systolic ambulatory blood pressure and minimisation factors. The treatment effect was similar for age, sex, and fifth of deprivation index (fig 2).
Table 2 Daytime ambulatory systolic and diastolic blood pressures over course of study in 359 participants with complete primary outcome data
Fig 2 Subgroup analyses on primary outcome of average daytime ambulatory systolic blood pressure measured at six months
In a sensitivity analysis using multiple imputation to allow for missing outcome data, the mean difference was 4.5 mm Hg (95% confidence interval 2.5 to 6.6; P<0.001). In addition we carried out a retrospective cluster analysis. The intraclass correlation coefficient was 0.02, and the point estimate after adjustment for clustering was 4.06 (95% confidence interval 1.43 to 6.68), P=0.0034. There was no evidence of between centre heterogeneity.
The mean daytime diastolic ambulatory blood pressure also fell in both arms (table 2), from 87.4 mm Hg to 83.4 mm Hg in the telemonitoring arm and from 85.7 mm Hg to 84.3 mm Hg in the usual care arm. The difference in mean daytime diastolic ambulatory blood pressure at six months between the two arms (usual care minus telemonitored) was 2.3 mm Hg (95% confidence interval 0.9 to 3.6; P=0.001), adjusted for baseline mean daytime diastolic ambulatory blood pressure and minimisation factors.
The difference in mean surgery measured systolic blood pressure at six months between the two groups (usual care minus intervention) was 4.6 mm Hg (95% confidence interval 1.7 to 7.5; P=0.0017) and for surgery measured diastolic blood pressure was 2.8 mm Hg (1.0 to 4.6; P=0.0021), adjusted for baseline surgery blood pressure and minimisation factors (table 3).
Table 3 Mean of second and third surgery measured systolic and diastolic blood pressures over course of study in 374 participants with surgery measured blood pressure results
Intervention and usual care groups did not differ significantly in the secondary outcome measures of self reported adherence to drugs, potential indicators of lifestyle adjustment (weight, spot sodium:creatinine ratio, cholesterol level, HbA1c level), self assessed therapy adherence, anxiety, health related quality of life, or exercise tolerance (table 4).
Table 4 Results at six month follow-up. Values are numbers (percentages) unless stated otherwise Number of drugs and defined daily dosage
At follow-up more participants were taking two or three antihypertensive drugs compared with at baseline (fig 3 and table 5). More participants in the telemonitoring arm than in the usual care arm had an increase in the number of drugs (P<0.001). There were increases in drug use across all the main drug groups, with calcium antagonists showing the biggest rise (table 6).
Fig 3Number of antihypertensive drugs by randomised group and follow-up point
Table 5 Change in hypertensive drug use at follow-up. Values are number (percentage) unless stated otherwise
Table 6 Patterns of antihypertensive drug group prescribing for patients with primary outcome data
In a retrospective comparison we found that the treatment intensity in the telemonitoring group also increased, with 76 (39%) of participants in the telemonitoring group increasing their defined daily dosage of antihypertensive drugs compared with 22 (12%) of participants in the usual care group (P=0.0003).
A full description of NHS resource use is presented elsewhere.27
After multiple imputation the mean NHS costs (excluding hospital admissions) per patient over the six month intervention period were significantly higher in the telemonitoring group than in the usual care group, by approximately £109.32 ($173.41; €130.24). The increase in costs was predominantly driven by the estimated intervention costs (£70.77), including monitor, mobile phone, and connection charges; server and web hosting; and the time it took nurses to check the website weekly. In addition significant increases in costs were associated with participants in the telemonitoring group using on average one additional general practitioner surgery consultation (£32.89), half of a practice nurse surgery consultation (£5.86), and half of a practice nurse telephone consultation (£2.57, table 7).
Table 7 Results from resource use survey
Compliance with the intervention
Participants in the telemonitoring arm took a median of 76 blood pressure readings, and 178 (89%) completed more than 90% of the expected minimum number of readings during the trial. Five people requested to stop using the home monitor of whom three subsequently withdrew (with the other two continuing until the end of the trial).
In total, 43 adverse events were recorded. One death occurred in the intervention group and two in the usual care group, none of which were thought to be related to blood pressure. The other events included three people who reported anxiety as a result of self monitoring, one who had a fall, and two who fainted (which may have been related to blood pressure control), and six seen in hospital because of cardiovascular problems (two atrial fibrillation, two chest pain, two very high blood pressure). In addition, one patient had a rash thought to be due to antihypertensive drug therapy and one developed hyperkalaemia secondary to dehydration and a viral illness but that was possibly exacerbated by antihypertensive drug therapy. The remainder had hospital admissions thought to be unrelated to blood pressure or the intervention. Apart from the three who had become anxious as a result of self monitoring, adverse events were evenly distributed between the groups.
Qualitative process analysis
A full description of the process analysis is presented elsewhere.33
Interviews were conducted with 11 nurses, nine doctors, and 25 patient participants, representing a maximum variation sample of patients based on age, sex, and deprivation status of the practice. Patients were generally positive about the intervention, although it was associated with anxiety in a small number of cases. Patient participants and clinicians admitted that before the intervention they were reluctant to increase drugs based on single blood pressure measurements taken in the surgery. Patient participants thought that the process improved access to clinicians and to reliable shared data, around which it was possible to have more equitable and informed discussions. Telemonitoring measurements based on multiple readings were perceived to be more accurate, be difficult to ignore, and lead to action. In some cases the alerts warning of inadequate blood pressure control were considered intrusive and irritating, especially when the blood pressure drug had recently been adjusted or the blood pressure was only 1 or 2 mm Hg above target, and some asked for these to be switched off, although others believed that they kept them engaged with the process. Clinicians noted a perceived increase in workload as a result of the intervention, partly due to lack of integration with main electronic health records and routine working processes, which also meant that the online blood pressure record was not easily accessed by all members of the healthcare team. Nurses reported that some patients did not respond to requests to attend the surgery, and accessing patients by phone was also sometimes problematical. On the few occasions when email was used for communication this was considered to work well. Both patient participants and clinicians thought that over the long term, with improved integration into normal practice systems the intervention would eventually reduce the need for visits to the surgery.