This is well known so I'm unclear on why this was removed.   See
author = {Hanley, J. A. and McNeil, B. J.},
  year = 1982,
  title = {The meaning and use of the area under a receiver operating
          characteristic ({ROC}) curve},
  journal = {Radiology},
  volume = 143,
  pages = {29-36},
  annote = {diagnosis;testing;ROC;c index}
}