Sensitivity | The proportion of episodes that were followed by a repeat self-harm episode and were correctly identified by the scale as high risk |
Specificity | The proportion of episodes that were not followed by a repeat self-harm episode and were correctly identified by the scale as low risk |
Positive predictive value | The probability that the episode identified as high risk by the scale was followed by repeat self-harm |
Negative predictive value | The probability that the episode identified as low risk by the scale was not followed by repeat self-harm |
Positive likelihood ratio | The increased likelihood of a high-risk scale result in an episode that is followed by repeat self-harm versus one that is not |
Negative likelihood ratio | The decreased likelihood of a low-risk scale result in an episode that is followed by repeat self-harm versus one that is not |
Diagnostic odds ratio | The odds of a high-risk result in an episode that is followed by repeat self-harm versus one that is not (interpreted the same as an odds ratio) |
Receiver operating characteristic (ROC) curve | Graphically shows the overall discrimination ability of a scale to identify episodes that were followed by a repeat self-harm episode compared with those that did not at various cut-off points (plotted as sensitivity versus 1-specifcity). The performance of the scale is indicated by the calculation of the area under the curve (AUC). Higher AUC indicate greater discriminatory power. |