15% home blood pressure monitors give wrong readings. Wrong readings here mean measurement error is bigger than 10mmHg. Question here is how significant is this 10mmHg error? What is the impact?
Before we analyze the question, we need to clarify that the measurement error is not for a single measurement. As we know, blood pressures always fluctuate, which could mask the error of measurement. Here the error we are talking about is the offset of average value, either average of several times or over a period such as several days. For example, if you measure your blood pressure with a traditional sphygmomanometer, the average reading could be 85mmHg for diastolic pressure. If you measure with an automated one, the reading could be 75mmHg or 95mmHg, which is 85mmHg+/-10mmHg. Remember, the possibility to get such error is 15%. So the answer is clear, your true blood pressure 85mmHg is in the range of prehypertension that means you may need to make some adjustment of your life style and habit and maybe medicine is still not necessary.
If the monitor over-estimates the number by 10mmHg, you are in the hypertension range and definitely you will need some treatment such as taking medicine. If the monitor under-estimates the number by 10mmHg, your number suggests that your blood pressure is very healthy and you don’t need to take any action. 10mmHg difference has totally affected the diagnosis and treatment though it might not endanger your life. The wrong treatment will induce silent hurt on your health. For example, the unmanaged blood pressure could damage your heart and kidney. It is so silent that people might ignore these hurt until it is too late.