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Interarm blood pressure measurement and the reference-arm assignment variability

Vinyoles, Ernesta; Tafalla, Martaa; Robledo, Vanesab; Marco, Martab; Porta, Isabelb; Muñoz, Miguel-Angelc; Fernández-San-Martin, M. Isabelc

doi: 10.1097/MBP.0000000000000394
Analytical Methods
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Objective The arm with the higher blood pressure (BP) is assigned as the follow up arm for hypertensive patients (reference-arm). We evaluated the reproducibility of this assignment.

Methods BP was measured simultaneously on both arms with a double cuff validated device in two visits separated <10 days (two sets of three readings per visit). Two reference-arms were assigned in each visit (the arm with higher BP, at least ≥1 mmHg). The intravisit and intervisit agreements of this assignment were evaluated.

Results We included 313 hypertensive patients. First visit mean right arm BP was 131.6 (16.6)/75.3 (9.4) mmHg and left arm BP was 132.4 (16.9)/75.7 (9.7) mmHg (P = 0.002). Intravisit concordance at the first and second visits were κ = 0.60 [95% confidence interval (CI), 0.516–0.696] and κ = 0.45 [95% CI, 0.356–0.555], respectively. Therefore, 21.8% of patients (at the first visit) and 29.1% (at the second visit) with the right arm as the reference-arm in the first round of readings changed to the left arm in the same visit in the second round of readings. The intervisit κ index was 0.25 [95% CI, 0.147–0.365]. After that, 36.8% of patients with the right arm as the reference-arm at the first visit changed to the left arm at the second visit. The subgroup (9.5%) with an interarm systolic BP difference ≥10 mmHg at the first visit did not differ significantly from the rest of patients.

Conclusion The reference-arm assignment agreement is weak to moderate. The assignment of the reference-arm should be individualized and not considered as definitive.

aLa Mina Primary Care Health Centre, University of Barcelona

bCasernes Primary Care Health Centre

cBarcelona Research Support Unit, Catalan Health Institute, Barcelona, Spain.

Received 19 March 2019 Accepted 13 June 2019

Correspondence to Ernest Vinyoles, MD, PhD, CAP La Mina, Plaça M Àngels Rossell Simplicio, s/n. 08930 – Sant Adrià de Besòs, Barcelona, Spain, Tel: + 34 933811593; fax + 34 933812141; e-mail: 23561evb@comb.cat

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