[Assessment of diagnostic procedures. Some comments about classical indices (author's transl)].

The assessment of diagnostic technologies, concerns today both clinicians and health care administrators. This assessment is based upon calculation of various indices measuring the informative value of diagnostic test: sensitivity, specificity, accuracy, predictive value. Despite their extreme semplicity, these indices can be misinterpreted and misused; in addition they are often calculated from very particular patients sample, especially when retrospective data are used. The main points which influence the value confered to a diagnostic test, the major bias to avoid designing such studies are pointed out this paper. The likeness between controlled therapeutic trial and comparative assessment of diagnostic technologies is particularly emphasized.