Table 3.
EBE accuracy metrics for sleep/wake and sleep stages detection
| EBE metric | Binary definition (sleep/wake) | Categorical definition (sleep staging) |
|---|---|---|
| Sensitivity | Proportion of “true” sleep epochs (i.e. based on the reference) that are correctly classified as sleep by the device. | Proportion of epochs classified as a given sleep stage by the reference that are correctly classified as that stage by the device. |
| Specificity | Proportion of “true” wake epochs (i.e. based on the reference) that are correctly classified as wake by the device. | Proportion of epochs not classified as a given stage by the reference that are correctly not classified as that stage by the device. |
| Accuracy | Proportion of correctly classified sleep and wake epochs over the total number of epochs. | Proportion of correctly classified epochs for a given stage over the total number of epochs. |
| PPV | Proportion of epochs classified as sleep by the device that are “true” sleep epochs (i.e. based on the reference). | Proportion of epochs classified as a target stage by the device that are classified as that stage by the reference. |
| NPV | Proportion of epochs classified as wake by the device that are “true” wake epochs (i.e. based on the reference). | Proportion of epochs not classified as a target stage by the device that are not classified as that stage by the reference. |
| PI | Proportion of “true” sleep epochs (i.e. based on the reference) over the total number of epochs. | Proportion of epochs classified as a target stage by the reference over the total number of epochs. |
| BI | Difference in sleep epoch proportion (i.e. sleep epochs over the total number of epochs) between device and reference. | Difference between device and reference in the proportion of epochs classified as a target stage over the total number of epochs. |
Metrics are defined based on proportions (generally ranging from 0 to 1), but it is common to report them as percentages, by simply multiplying the result by 100. PPV, positive predictive value; NPV, negative predictive value; PI, Prevalence Index; BI, Bias Index.