[DISCLAIMER: I am the author of the referenced documents] This post proposes incorporating a generalization of ROC curve analysis into SAS statistical subroutines (e.g., PROCS LOGISTIC and GENMOD). This generalized method is straightforward to implement and a git repository(1) is linked below with an implementation using PROC LOGISTIC. Classical ROC curve analysis is defined for binary outcomes comprising two levels, but extension to discrete outcomes comprising three or more levels would generalize its scope of applications. Although a variety of methods have been proposed to accomplish this, they tend to entail significant limitations, such as: restriction of the outcome to relatively few levels; reliance on valid, but somewhat abstruse theory; implementation only with specialized software. Another method has been described that extends ROC curve analysis to ordinal outcomes with three or more levels(2). The theoretical justification for this method -- "cumulative ROC curves" -- relies on the ROC curve's essential representation of a rank-based association between the discrete outcome and continuous predictor, as well as a straightforward interpretation of multinomial regression. Implementation is likewise straightforward, requiring only software for running multinomial regression models, specifically, but not necessarily limited to the cumulative logit model. Consequently, cumulative ROC curve analysis is suitable for a general scope of applications while also being accessible to quantitative tools already established for characterizing binary ROC curves, such as sensitivity, specificity, area-under-the-curve, Total Accuracy, and Youden's Index. In particular, these established tools can be directly applied to identifying cutpoints on the continuous measurement scale that discriminate between successive levels of the ordinal outcome. Cumulative ROC curves have been shown in simulations to perform as expected. References 1. [REPOSITORY] deCastro, B.R. (2019). %cumRoc3 --- Cumulative ROC curve analysis of three-level ordinal outcomes (1.0.1). https://doi.org/10.5281/zenodo.3364094. 2. deCastro, B.R. (2019). Cumulative ROC curves for discriminating three or more ordinal outcomes with cutpoints on a shared continuous measurement scale. PLoS ONE, 14(8). https://doi.org/10.1371/journal.pone.0221433.
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