Causes of Inaccurate Blood Pressure Measurements
How to properly take the blood pressure
See the following links.
https://jamanetwork.com/journals/jama/fullarticle/2643764
https://wire.ama-assn.org/delivering-care/one-graphic-you-need-accurate-blood-pressure-reading
https://wire.ama-assn.org/delivering-care/how-get-most-accurate-blood-pressure-measurement
http://www.heart.org/HEARTORG/Conditions/HighBloodPressure/KnowYourNumbers/Monitoring-Your-Blood-Pressure-at-Home_UCM_301874_Article.jsp#.WuHhFlMvyi4