Manual BP devices linked to common source of measurement errors

A common source of BP measurement errors known as terminal digit bias — “an observer’s preference for a last digit, usually 0, and a tendency to round up or down the BP measurement to that digit” — often occurred when nurses used a manual device instead of an automated device, researchers reported in the Journal of the American Board of Family Medicine.

Researchers also determined that measuring patients’ BP when they were on the examination room table instead of a chair led to erroneous diagnoses more than 10% of the time.

Roy N. Morcos , MD, FAAFP, practitioner within the department of family and community medicine at Northeast Ohio Medical University, and colleagues analyzed 3,000 BP measurements that were recorded manually by three nurses (n = 1,500) and by an automated device (n = 1,500) for terminal digit bias. In addition, 294 patients (median age, 50.5 years; 63.9% women) had four BP measurements — twice while seated on an examination room table and twice while seated in a chair — taken via an automatic device.

Morcos and colleagues predicted that 150 of the 1,500 BP measurements with a manual device would end in 0. However, the researchers found that 350 of the BP measurements obtained via a manual device ended in 0, showing a “highly significant” bias for that digit (P < .01). No such bias occurred in the 1,500 BPs measurements obtained via an automated device.

The researchers also observed significant BP lowering in nearly half of patients (42.7%) when measurements were obtained in the chair position vs. the examination table position. The BP measurements from the examination room table resulted in a misdiagnosis of prehypertension 15.3% of the time and a misdiagnosis of hypertension 16% of the time.

“These results confirm the importance of proper patient positioning in a comfortable chair when measuring BP,” Morcos and colleagues wrote, adding that the results also “confirm the potential advantage of automated devices in obtaining an accurate and reliable office BP measurement.”

Researchers added that a 10 mm Hg decrease in systolic BP can significantly lower a patient’s risk for coronary artery disease, heart failure and stroke, adding a layer of importance to obtaining the patient’s correct systolic BP. – by Janel Miller

Disclosures: The authors report no relevant financial disclosures.