Initial blood pressure (BP) measurements in patients with diabetes should be taken from both arms, say researchers.
The UK team found that 8.6% of 726 diabetes patients in their study had an interarm difference in systolic BP (SBP) of at least 10 mmHg, compared with just 2.9% of 285 nondiabetic controls.
Furthermore, having a difference of at least 10 mmHg was associated with a 3.5-fold increased risk of cardiovascular mortality during a median 4.3 years of follow-up, and having at least a 15 mmHg difference was associated with a ninefold risk increase.
“In therapeutic terms, there is no evidence to support any different intervention on detection of a difference, but in a health service of finite and shrinking resources, this may help to identify subjects who can most benefit from intensive lifestyle interventions”, say lead researcher Christopher Clark (University of Exeter Medical School, UK) and co-workers.
Having an interarm SBP difference was also associated with morbidity at baseline, independently of multiple confounders. Specifically, a 10 mmHg difference was associated with a 3.4-fold increased likelihood of having peripheral arterial disease and a 15 mmHg difference conferred 5.7- and sevenfold increased likelihoods of having diabetic retinopathy and chronic kidney disease, respectively.
Of note, the researchers found that one simultaneous measurement of SBP in both arms was sufficient to establish an interarm difference. They took up to four simultaneous measurements in each patient, but found that a single paired measurement was up to 79% accurate relative to four measurements, with a negative predictive value of up to 99%.
Clark et al also note that paired measurements failed entirely in 11.5% of patients. “The number of failed attempts to measure pairs of blood pressures brings into question the practicality of repeated simultaneous measures in clinical practice”, they write in Diabetes Care.
The most common reasons for failure to obtain a paired measurement were machine errors (in 36 of 116 patients) and the presence of arrhythmias, predominantly atrial fibrillation (in 25 patients). Four paired readings were not obtained in any patient with arrhythmia, note the researchers, who add that this “is a recognized problem with automated sphygmomanometers”.
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