Objective Simple forms of blood pressure (BP) telemonitoring require patients to text readings to central servers creating an opportunity for both entry error and manipulation. We wished to determine if there was an apparent preference for particular end digits and entries which were just below target BPs which might suggest evidence of data manipulation.
Design Prospective cohort study
Setting 37 socioeconomically diverse primary care practices from South East Scotland.
Participants Patients were recruited with hypertension to a telemonitoring service in which patients submitted home BP readings by manually transcribing the measurements into text messages for transmission (‘patient-texted system’). These readings were compared with those from primary care patients with uncontrolled hypertension using a system in which readings were automatically transmitted, eliminating the possibility of manipulation of values (‘automatic-transmission system’).
Methods A generalised estimating equations method was used to compare BP readings between the patient-texted and automatic-transmission systems, while taking into account clustering of readings within patients.
Results A total of 44 150 BP readings were analysed on 1068 patients using the patient-texted system compared with 20 705 readings on 199 patients using the automatic-transmission system. Compared with the automatic-transmission data, the patient-texted data showed a significantly higher proportion of occurrences of both systolic and diastolic BP having a zero end digit (OR 2.1, 95% CI 1.7 to 2.6) although incidence was <2% of readings. Similarly, there was a preference for systolic 134 and diastolic 84 (the threshold for alerts was 135/85) (134 systolic BP OR 1.5, 95% CI 1.3 to 1.8; 84 diastolic BP OR 1.5, 95% CI 1.3 to 1.9).
Conclusion End-digit preference for zero numbers and specific-value preference for readings just below the alert threshold exist among patients in self-reporting their BP using telemonitoring. However, the proportion of readings affected is small and unlikely to be clinically important.
Trial registration number ISRCTN72614272; Post-results.
- end digit preference
- terminal digit preference
- blood pressure control
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Contributors BM, PP, HP, JH and AS made substantial contributions to the conception and design of the work. MP and VSH monitored the implementation of the telemonitoring system and co-ordinated the study. MP acquired the raw data. RAP planned and performed the statistical analysis. RAP wrote the first draft of the paper. All authors revised and commented on the manuscript.
Funding This work was supported by the Chief Scientists Office of the Scottish Government (reference number CZH/4/1135). The Scale-Up BP project is supported by the Scottish Government Technology Enabled Care Programme and the HITS study was supported by the BUPA foundation (reference number 748/G24).
Competing interests None declared.
Patient consent Obtained.
Ethics approval The HITS trial had ethical approval from the South East Scotland Research Ethics Committee (reference number 08/S1101/38).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The dataset used in this study is available for download from figshare, DOI: 10.6084/m9.figshare.5363428
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