[What benefit and harm can be expected from screening and routine examinations and from their omission?]

Benefit and harm of screening and routine tests or their omission are dealt with in four parts. In the first part methods are described to evaluate the diagnostic value of medical testing. The concepts of diagnostic sensitivity, diagnostic specificity, and pre- and posttest probability of a diagnosis are defined. It is then shown how these concepts intercorrelate and how their numerical values can be calculated ("Bayes" theorem"). In consideration of the above mentioned intercorrelations, the second and third parts deal with the diagnostic value of preoperative routine tests from an anaesthesiological viewpoint, and the diagnostic value of other screening and follow-up tests is discussed from a gynaecological point of view. Pre-operative laboratory tests are necessary, and necessary only then, if careful evaluation of patient history and physical examination reveal pathological findings or risk factors. The benefits from regular lab-screening tests and follow-up tests, as recommended to the gynaecologists, are low. This is due to the large share of "healthy" women among the gynaecological patients, as well as the fact that treatment of early detected recurrences shows no demonstrable advantage over treatment of later detected recurrences. In the fourth part, we show that no adverse forensic consequences are to be expected if diagnostic tests are omitted because of demonstrably low diagnostic value. In case of legal procedures against the physician, a medical expert will have to evaluate the diagnostic value of the omitted test objectively from an "ex-ante" point of view, using the methods defined in the first part.(ABSTRACT TRUNCATED AT 250 WORDS)