[Receiver operating curve, an aid in decision making. Principles and applications illustrated with some examples].

The practitioner has many difficult questions to resolve when he has placed in front of him more and more diagnostic and screening tests. Which is, in a given situation, the best test, by which is meant useful, least costly and most acceptable by the patient? Having chosen the test, at what level is the result to be considered positive or negative? The authors, having explained the principles and having taken some examples out of the literature of gynaecology and obstetrics, present a technique that shows on a receiver operating characteristic curve sensitivity and specificity sharing as a function of the possible levels for making decisions according to the test. The curve inordinate shows the sensitivity of the test or the number of true positives and on the abscissa the complement of specificity or the rate of false positives ford each decision threshold of the test. A simple glance gives the practitioner a view of the characteristics of the test over the whole band that this test can use. Using these curves it is possible to adopt more elaborate techniques to select the best threshold and to compare different tests.