Consider again the simple logistic regression model. We found that the apparent ROC area was 0.77. When tested in 20,318 patients from other centers in the GUSTO-I data set, the area was 0.74. The decrease of 0.03 was slightly more than expected by internal validation (decrease 0.01).

The external validity is also shown on the next slide. A fully external validation (other place, other investigators) was not yet performed.