Abstract
BackgroundScale-up BP was a quasi-experimental implementation study, following a successful randomised controlled trial of the roll-out of telemonitoring in primary care across Lothian, Scotland. Our primary objective was to assess the effect of telemonitoring on blood pressure (BP) control using routinely collected data. Telemonitored systolic and diastolic BP were compared with surgery BP measurements from patients not using telemonitoring (comparator patients). The statistical analysis and interpretation of findings was challenging due to the broad range of biases potentially influencing the results, including differences in the frequency of readings, ‘white coat effect’, end digit preference, and missing data.MethodsFour different statistical methods were employed in order to minimise the impact of these biases on the comparison between telemonitoring and comparator groups. These methods were “standardisation with stratification”, “standardisation with matching”, “regression adjustment for propensity score” and “random coefficient modelling”. The first three methods standardised the groups so that all participants provided exactly two measurements at baseline and 6–12 months follow-up prior to analysis. The fourth analysis used linear mixed modelling based on all available data.ResultsThe standardisation with stratification analysis showed a significantly lower systolic BP in telemonitoring patients at 6–12 months follow-up (-4.06, 95% CI -6.30 to -1.82, p < 0.001) for patients with systolic BP below 135 at baseline. For the standardisation with matching and regression adjustment for propensity score analyses, systolic BP was significantly lower overall (− 5.96, 95% CI -8.36 to − 3.55 , p < 0.001) and (− 3.73, 95% CI− 5.34 to − 2.13, p < 0.001) respectively, even after assuming that − 5 of the difference was due to ‘white coat effect’. For the random coefficient modelling, the improvement in systolic BP was estimated to be -3.37 (95% CI -5.41 to -1.33 , p < 0.001) after 1 year.ConclusionsThe four analyses provide additional evidence for the effectiveness of telemonitoring in controlling BP in routine primary care. The random coefficient analysis is particularly recommended due to its ability to utilise all available data. However, adjusting for the complex array of biases was difficult. Researchers should appreciate the potential for bias in implementation studies and seek to acquire a detailed understanding of the study context in order to design appropriate analytical approaches.
Highlights
Scale-up blood pressure (BP) was a quasi-experimental implementation study, following a successful randomised controlled trial of the roll-out of telemonitoring in primary care across Lothian, Scotland
In this article we present the results of an in-depth analysis employing a range of methods to investigate if telemonitoring improves BP control when routinely implemented at scale, while illustrating some of the challenges involved with evaluating effectiveness in a quasi-experimental study involving routinely acquired data
In the model we considered within-patient time instead of calendar time because we were primarily interested in how BP changed over time within patients after they started using telemonitoring rather than changes over calendar time, which may have been confounded by systematic differences in the recruited population over time as practices rolled out the service
Summary
Scale-up BP was a quasi-experimental implementation study, following a successful randomised controlled trial of the roll-out of telemonitoring in primary care across Lothian, Scotland. When combined with the collection of longitudinal data from electronic health records or data which are otherwise routinely acquired, these evaluation studies are data rich in terms of the information they provide, but are often based on patient populations that are highly generalisable and representative of the target population [1, 2]. Participants used an electronic oscillometric sphygmomanometer to measure BP and submitted BP readings via their own mobile phone using a low-cost third-party textbased telemonitoring system procured by the Scottish Government (Florence) [5] These patient-generated BP readings were stored in a central server and made available to practices via an Internet link. The Scottish Government’s Technology Enabled Care (TEC) fund [7] financed the third-party telemonitoring service, the development of the software to link it with GP systems using Docman, supported facilitators to visit/train practices, and purchased sphygmomanometers for loan to patients
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