Diagnostic performance of an automatic blood pressure measurement device, Microlife WatchBP Home A, for atrial fibrillation screening in a real-world primary care setting

Abstract

Objective: To evaluate the diagnostic performance of a UK National Institute for Health and Care Excellence-recommended automatic oscillometric blood pressure (BP) measurement device incorporated with an atrial fibrillation (AF) detection algorithm (Microlife WatchBP Home A) for real-world AF screening in a primary healthcare setting.

Setting: Primary healthcare setting in Hong Kong.

Interventions: This was a prospective AF screening study carried out between 1 September 2014 and 14 January 2015. The Microlife device was evaluated for AF detection and compared with a reference standard of lead-I ECG.

Primary outcome measures: Diagnostic performance of Microlife for AF detection.

Results: 5969 patients (mean age: 67.2±11.0 years; 53.9% female) were recruited. The mean CHA₂DS₂-VASc ( C : congestive heart failure [1 point]; H : hypertension [1 point]; A₂ : age 65-74 years [1 point] and age ≥75 years [2 points]; D : diabetes mellitus [1 point]; S : prior stroke or transient ischemic attack [2 points]; VA : vascular disease [1 point]; and Sc : sex category [female] [1 point])score was 2.8±1.3. AF was diagnosed in 72 patients (1.21%) and confirmed by a 12-lead ECG. The Microlife device correctly identified AF in 58 patients and produced 79 false-positives. The corresponding sensitivity and specificity for AF detection were 80.6% (95% CI 69.5 to 88.9) and 98.7% (95% CI 98.3 to 98.9), respectively. Among patients with a false-positive by the Microlife device, 30.4% had sinus rhythm, 35.4% had sinus arrhythmia and 29.1% exhibited premature atrial complexes. With the low prevalence of AF in this population, the positive and negative predictive values of Microlife device for AF detection were 42.4% (95% CI 34.0 to 51.2) and 99.8% (95% CI 99.6 to 99.9), respectively. The overall diagnostic performance of Microlife device to detect AF as determined by area under the curves was 0.90 (95% CI 0.89 to 0.90).

Conclusions: In the primary care setting, Microlife WatchBP Home was an effective means to screen for AF, with a reasonable sensitivity of 80.6% and a high negative predictive value of 99.8%, in addition to its routine function of BP measurement. In a younger patient population aged <65 years with a lower prevalence of AF, Microlife WatchBP Home A demonstrated a similar diagnostic accuracy.

Keywords: Atrial fibrillation; microlife; screening.

Figure 1

Study enrolment and flow.

Figure 2

(A) Rhythm diagnoses of the study population based on interpretation by two independent cardiologists of a 30 s bipolar lead-I ECG. (B) Prevalence of AF categorised into different age groups. AF, atrial fibrillation; PAC, premature atrial complex; PVC, premature ventricular complex

Figure 3

Contingency table for atrial fibrillation detection and rhythm diagnoses of an automatic oscillometric blood pressure measurement device incorporated with a specific algorithm for AF detection (Microlife WatchBP Home A). AF, atrial fibrillation; PAC, premature atrial complex; PVC, premature ventricular complex.