Simple tests for the external validation of mortality prediction scores

This paper is concerned with methods for the external validation of the prognostic scores that predict the probability of some event such as death. The problem is similar to that of testing the goodness-of-fit of a logistic regression model, except that the prognostic scores are not estimated and validated using the same data. A number of methods for assessing logistic model goodness-of-fit have been proposed, and some of these can also be used in the setting considered. A simple test based on the likelihood ratio statistic is proposed, which does not require arbitrary choice of groups or smoothing parameters. In a simulation study, the proposed method is found to be as powerful as commonly used methods under the scenarios considered.