Table 3.
Comparison of Bias (Accuracy), SD (Precision), and Root-Mean-Square Deviation of Test and Reference Measurement Systems, for Heart Rate and Oxygen Saturation, in Outpatient (n = 250) and Inpatient (n = 70) Studiesa
| Study Setting | Bias (Accuracy) Test vs Reference System |
SD (Precision) Each System |
Root-Mean-Square Deviation Each System |
|||||
|---|---|---|---|---|---|---|---|---|
| Testb | Referenceb | P Value | Test | Reference | P Value | Test | Reference | |
| Outpatient study | ||||||||
| Heart rate, bpm (95% CI) | 0.73 (0.33 to 1.14) | 0 (ref) | < .001 | 5.99 (5.61 to 6.40) | 3.80 (3.56 to 4.06) | < .001 | 6.03 (5.47 to 6.60) | 3.80 (3.56 to 4.06) |
| Spo2, % points (95% CI) | 0.48 (0.38 to 0.58) | 0 (ref) | < .001 | 1.25 (1.17 to 1.33) | 0.95 (0.89 to 1.01) | < .001 | 1.34 (1.21 to 1.47) | 0.95 (0.89 to 1.01) |
| Inpatient study | ||||||||
| Heart rate, bpm (95% CI) | –0.19 (–1.59 to 1.22) | 0 (ref) | .79 | 6.58 (5.78 to 7.49) | 4.99 (4.39 to 5.69) | .004 | 6.58 (4.94 to 8.23) | 4.99 (4.39 to 5.69) |
| Spo2, % points (95% CI) | –0.94 (–1.41 to –0.47) | 0 (ref) | < .001 | 2.62 (2.31 to 2.97) | 0.89 (0.78 to 1.01) | < .001 | 2.78 (2.21 to 3.36) | 0.89 (0.78 to 1.01) |
The bias comparison used the Wald test of mixed-effects linear model. ref = reference; Spo2 = oxygen saturation.
a
The reference system by definition has no bias and RMSD = SD. Bias and SD correspond to β2 and SD (εij), respectively, in model Equation 2 (see Methods).
b
Test = in-phone measurement system; Reference = Spot Vital Signs measurement system (Welch Allyn).