specificity, the positive and negative predictive values are dependent on the risk score threshold T. These statistics can be used to tune the parameter T: for instance, while in the example above a test of a 1% disease with an AUC of 0.98 had a PPV of 12% and a sensitivity of 93%, by raising the threshold we could also produce a test with a sensitivity of only 40%, but a PPV of 75%. This test would miss a larger proportion of people with the disease, but would have much higher confidence that those it caught will go on to show symptoms.
