models are complex.
Performance of Prediction ModelsWe need to assess the performance of risk prediction models more carefully before applying their results in the clinical setting. The performance of risk prediction models is divided into two components: discrimination and calibration. 6 Discrimination is the ability of the prediction model to distinguish whether high-risk patients are in fact low risk. 6 A well-known measurement tool of discrimination is the receiver-operating characteristic (ROC) curve or the C-statistic. The C-statistic defines the probability that a randomly selected patient who developed an event had a higher risk score than a patient who had not developed the event. The ROC curve draws the plot of the sensitivity and (1−specificity) for all possible cutoff points (Figure 1). When the outcome is a binary event, the area under the ROC curve (AUC) is equivalent to the C-statistic, which ranges from 0.5 to 1, where 0.5 indicates no discriminatory ability and P redicting a patient's prognosis advances medical decision making in clinical settings. Risk prediction models (also called prognostic models, prediction rules, or risk scores) are tools to estimate individual patients' risk or probability by numerical values. Although many prediction models have been published, few have been used in routine clinical settings because of inconvenience and complexity. 1 In this issue of the Journal, Hu et al show how they applied the CHA2DS2-VASc score to predict the incidence of atrial fibrillation (AF) in chronic obstructive pulmonary disease (COPD) patients. 2 Previous studies have reported prediction models for AF based on community cohorts, 3-5 but most cardiologists are not familiar with these community-based prediction models. It seems reasonable to evaluate individual risk with what we already know, but we must be aware that CHA2DS2-VASc score was developed as the model for predicting ischemic stroke in patients with AF, not for incident AF in COPD patients. It is possible that applying the wrong prediction model may cause overor underestimation of a patient's risk. In order to reduce this, we need to understand the evaluation methods, risk prediction models and the reasons why high-performance
Article p 1792The opinions expressed in this article are not necessarily those of the editors or of the Japanese Circulation Society.