Table 4.
Comparison of Bias (Accuracy) and SD (Precision) for Heart Rate and Oxygen Saturation Within Test Unit (Smartphone Sensor With App) and Within Reference Unit (Welch Allyn Spot Vital Signs) Measurement Systems in Outpatient Study (n = 250)a,b
| Vital Sign | Model | Bias (Accuracy) Within System |
SD (Precision) Within System |
|||
|---|---|---|---|---|---|---|
| Unit 1-Unit 2 | P Value | Unit 1 | Unit 2 | P Value | ||
| Heart rate, bpm | Test units | –0.36 (–0.99 to 0.27) | .27 | 6.92 (6.42 to 7.46) | 4.95 (4.60 to 5.34) | < .001 |
| Reference units | –0.33 (–0.66 to 0.00) | .049 | 3.86 (3.58 to 4.16) | 3.65 (3.39 to 3.94) | .27 | |
| Spo2, % points | Test units | –0.06 (–0.22 to 0.10) | .43 | 1.26 (1.04 to 1.52) | 1.25 (1.03 to 1.51) | .90 |
| Reference units | 0.52 (0.41 to 0.64) | < .001 | 1.01 (0.84 to 1.22) | 0.86 (0.71 to 1.04) | .001 | |
The bias comparison used the Wald test of mixed-effects linear model. The SD comparison used the likelihood ratio test of the mixed-effects linear model. See Table 3 legend for expansion of abbreviation.
a
Bias corresponds to β3 (test units) and to β4 (reference units), and SD corresponds to SD (εij) in model Equation 2 (see Methods).
b
Test units, smartphone sensor with app; reference units, Spot Vital Signs (Welch Allyn).