Are self-reported telemonitored blood pressure readings affected by end-digit preference: a prospective cohort study in Scotland

Abstract

ObjectiveSimple 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.DesignProspective cohort studySetting37 socioeconomically diverse primary care practices from South East Scotland.ParticipantsPatients 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’).MethodsA 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.ResultsA 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).ConclusionEnd-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.

Sources of Error in Office Blood Pressure Measurement

“…No such bias was identified with any of the same 3 nurses using an automated device. This TDB was previously described in numerous other studies, 19,[21][22][23][24][25][26][27][28][29] most of which show that TDB is reduced but not completely eliminated by the introduction of automated devices in measuring BP. Myers and Campbell 11 found evidence of TDB of 14% of readings when using the BpTRU automated device, when the expected proportion of zero terminal digits is 10%.…”

Value-based approach to blood pressure telemonitoring and remote counseling in hypertensive patients

“…Telemonitoring may enhance the quality of reported information and facilitate its interpretation. In our study manual transcription of measured BP values in the app presents a challenge of inaccurate BP data input leading to a terminal (end) digit bias [17]. Further improvement of our system is to add the option of automated data transmission from HBPM device to the app and then to a clinician to ensure all the measurements will be stored and analysed properly [18].…”

A cluster‐randomized study on the Risk Assessment and Management Program for home blood pressure monitoring in an older population with inadequate health literacy

“…Firstly, only office BP was recorded in all outcome measures. To assess a more comprehensive BP reading, the study outcomes may include ambulatory BP readings or home BP readings by HBPM device with digital memory or wireless transmission functions 38 . Secondly, since we had a limited number of HBPM devices, participants have to take turns to use the HBPM devices over the study period.…”