Routine blood pressure measurements in people under 35 years of age may often lead to a misdiagnosis of high blood pressure, the results of a study in the British Medical Journal suggests.
Blood pressure varies randomly from beat to beat, and any measurement is only an estimate of the true average blood pressure, notes public health lecturer Tom Marshall in his study. Guidelines recommend that doctors use three measurements when deciding whether to treat patients for high blood pressure, or hypertension. The variation within individuals for the top reading of the blood pressure, or systolic pressure, is nearly 10 percent. The variation for the blood pressure bottom reading, or diastolic pressure, is about nine percent, notes Marshall, who is based at the University of Birmingham. Using these figures and data from health surveys for England in 1998-2000, he calculated the values of three blood pressure measurements for men and women by age.
The predictive value of blood pressure estimates was highest in older age groups and lowest in younger people, he reports. Of 36 men between 16 and 34 years old who were classified as needing treatment, only 11 were true positives. Of 19 women in the same age group, only five really needed treatment. “Routine measurement of blood pressure in persons under 35 is more likely to misdiagnose than to diagnose hypertension correctly,” Marshall writes. “As 10-year coronary risk rarely exceeds five percent in adults under 35, clinicians should diagnose hypertension with caution–perhaps at a higher threshold.” The main usefulness of blood pressure monitoring, he adds, is in people with specific conditions or risk factors for heart disease.
