Real-world performance of a ring-type cuffless blood pressure device compared with ambulatory blood pressure monitoring

Background: Cuffless blood pressure (BP) monitoring devices are convenient alternatives to conventional ambulatory blood pressure monitoring (ABPM). We evaluated the real-world agreement between a ring-type cuffless BP device (continuous ambulatory ring-type blood pressure monitor, CART BP pro) and ABPM and identified the clinical and physiological factors associated with measurement discrepancies. Methods: This real-world observational study included 154 adults (mean age, 62.1 ± 14.2 years; 41.6% men) who underwent simultaneous 24-hour ABPM and CART BP pro after exclusion of predefined clinical conditions and insufficient recordings. CART BP pro measurements were calibrated at baseline to ABPM in the contralateral arm. BP values from the 2 devices were compared for 24-hour, daytime, and nighttime periods, as well as for the classification of nocturnal hypertension and dipping status. Predictors of close systolic agreement (|24-hour systolic blood pressure [SBP] difference| ≤ 5 mmHg) were identified using multivariable logistic regression. Results: CART BP pro-derived period summaries were lower than ABPM for systolic BP (-7.1 mmHg for 24-hour SBP) and showed a modest positive bias for diastolic BP. Only 33.1% of measurements met the ≤ 5 mmHg accuracy criterion. Daytime SBP showed a similar bias (-7.8 mmHg), whereas nighttime SBP differences were smaller (-1.7 mmHg). By contrast, diastolic BP was consistently higher with the CART BP pro, particularly at night (+4.8 mmHg). Older age, male sex, lower body mass index, and higher heart rate independently predicted a closer systolic agreement. The agreement for nocturnal hypertension was moderate (κ = 0.516), with an overall concordance of 76.0%. However, dipping concordance was limited, with the CART BP pro showing blunted nocturnal dipping compared with ABPM (mean, 3.7% vs. 7.8%). Conclusions: This exploratory, real-world study found that CART BP pro-derived period summaries showed lower SBP values and smaller nocturnal BP declines than ABPM. Because period-level aggregates were compared rather than simultaneous point-to-point measurements, these findings should not be interpreted as a formal accuracy validation of the device. Further studies are needed to establish device-specific diagnostic thresholds and prospectively validate the clinical interpretation of CART BP pro-derived period summaries for hypertension diagnosis and circadian BP phenotyping.