Reliability of reporting self-measured blood pressure values by hypertensive patients

For self-measurement of blood pressure to be useful, patient reporting of t est results must be reliable and accurate. Until now no study directly meas ured the accuracy and reliability of patients' reporting of self-measured b lood pressure values. Thirty hypertensive patients (69 +/- 11 years) were instructed to measure b lood pressure at home over 14 days with the highly accurate Omron TC monito r and to keep a record of all readings in a patient logbook. To assess the reliability of the records, patients were not informed about the memory cap acity of the device. We compared automatically stored blood pressure readin gs with the respective logbook entries to analyze deletion (under-reporting ), addition (over-reporting), and precision of reporting of test results. The prevalent pattern was under-reporting, averaging 36% +/- 24% (3% to 89% ), which occurred significantly more than over-reporting (9% +/- 11%; 0% to 38%). The precision of reporting (identical values at corresponding times) was 76% +/- 34% (0% to 100%). This observer error did not affect group com parisons of automatically stored values and logbook entries, although the e stimated limits of agreement were wide. Blood pressure control, duration of hypertension, age, or previous use of self-measurement and patterns of log book entries were not found to be predictive of the patients' reliability. Our results demonstrate a substantial observer error in the reporting of se lf-measured blood pressure values. This bias may be reduced by memory-equip ped blood pressure devices. (C) 1998 American Journal of Hypertension, Ltd.