Quantitative concepts for the evaluation of diagnostic tests with regard to their value for diagnostics and therapy

The necessity of quantitative data describing the efficiency of diagnostic and therapeutic measures is pointed out. Possible parameters of diagnostic (or therapeutic) effectiveness are indication lists, decision trees (diagnostic strategies), sensitivity, specificity, accuracy, predictive value and ROC characteristics. These quantities and the mathematical relations between them are described. For chest X-ray screening the sensitivity is 0.84, specificity 0.90 and the respective predictive values are only 0.34% for cancer and 0.13% for tuberculosis. (author)