Letters

Rapid Responses from bmj.com

Use the sphygmomanometers more, not less

Ambulatory blood pressure monitoring: really a gold standard?

From BMJ USA 2002;October:553

As of September 19, 2002, this article had generated 11 Rapid Responses, which can be read in their entirety at http://bmj.com/cgi/eletters/325/7358/254. Edited excerpts from two responses are presented here.Editor

Use the sphygmomanometers more, not less

EDITORThe conclusion by Little et althat conventional measurements by general practitioners may be misleadingruns ahead of the evidence. The chain of evidence that is required to make this conclusion has three links: The first is a reliable method of measuring blood pressure, the second is demonstrating that raised blood pressure diagnosed by the chosen method increases the patient's cardiovascular risk, and the third is that treatment reduces the risk. As part of the last link it is valuable to know the absolute benefits of treatment, and what target blood pressure to aim for.

The research evidence for treatment decisions based on newer methods is not available for the last link. We know from well-conducted trials that treatment based on clinic readings reduces risk. These trials also give us evidence to support a target for treatment. This evidence is much weaker for newer methods of diagnosing and monitoring hypertension. In essence we have two different diagnoses: hypertension diagnosed conventionally and hypertension diagnosed otherwise. The epidemiology of the latter is currently much less understood.

Doctors should not discard their sphygmomanometers or give them to their nurses. Rather, they should use them more, so that clinical decisions are based on multiple readings. In this aspect we are wholly in agreement with the authors.

William Hamilton, research fellow. 
w.t.hamilton{at}btopenworld.com

Deborah Sharp, professor. 
Division of Primary Health Care, University of Bristol, Bristol, UK

Ambulatory blood pressure monitoring: really a gold standard?

EDITORThe results of this study are interpreted on the assumption that ambulatory blood pressure is the gold standard. To support this statement the authors quote several papers that claimed that ambulatory blood pressure is superior to clinic blood pressure in predicting outcomes. What those studies actually showed is that ambulatory blood pressure has a greater predictive value than a few clinic readings taken in one or two visits.

However, if clinic blood pressure is measured several times over an adequate period of observation, as suggested by current guidelines for patients with newly diagnosed mild hypertension, its predictive power may be superior to that of ambulatory measurement. More to the point, is there any published evidence that ambulatory blood pressure has a greater predictive value than that measured by the nurse, or by the patient at home or in the clinic? The authors claim that ambulatory blood pressure can give a reliable estimate of the white coat effect, but the few studies on this matter show that the difference between clinic and daytime blood pressure does not reflect the true white coat effect as measured with beat-by-beat recordings during doctors visits. Moreover, recent results indicate that home blood pressure measurement predicts white coat hypertension more precisely than does ambulatory blood pressure.

Although ambulatory monitoring can provide unique information on blood pressure variability in well-selected patients, there is no proof that mean daytime blood pressure is superior to self-measurement, nurse measurement, or clinic blood pressure measured repeatedly.

Paolo Palatini, professor of medicine. 
Department of Clinical and Experimental Medicine, University of Padua, Padua, Italy palatini{at}unipd.it