Receiver operating characteristic (ROC) curve of the ACPA model in the derivation and validation cohorts. (A) In the derivation cohort, the area under the ROC curve (AUC) of the ACPA model was 0.853 (95% CI, 0.818-0.889). (B) In the validation cohort, the AUC of the ACPA model was 0.862 (95% CI, 0.807-0.916).