Many of the previous entries in this review series have come from statisticians and epidemiologists who evaluate screening programmes and guide national policies for the health care of populations. Their calculations take into account the benefits for health and mortality, adverse consequences, cost-effectiveness and opportunity costs of obtaining evidence from trials and service screening [1
]. They largely use data from events in the past to make forward decisions. Likewise, many of the pathological data are obtained by observing the different pathological entities in longitudinal follow up of case material stored many years ago and linked with outcomes. By contrast, radiologists, with the patient and the clinical teams, make current decisions for individuals.
Overdiagnosis is the result of detecting cancers that would not present in the patient's life without screening. Radiologists consider issues of overdiagnosis but they seldom use this particular term. Considerable radiological effort has been applied to reducing false-positive recalls, which result in unnecessary surgery for benign disease. Some of this literature is relevant to the present issue of overdiagnosis, but in general when the radiologist finds a lesion labelled cancer by a pathologist, they and the patient regard this as a desirable event and the patient feels gratitude for a beneficial medical service.
This situation is not unique to screening. In the current international political debate on pensions, if individuals could foresee their year of death and predict future fiscal performance then they would make good decisions on pension investment and age of retirement. This example has an individual and a population dimension, because current demographic changes were not foreseen when earlier policies were laid down. To use an example from a symptomatic clinical setting, a patient presenting with chest symptoms and an area of shadowing on a chest radiograph will wish to take an antibiotic for pneumonia, although the diagnosis is not conclusive, the disease may be of viral origin and many bacterial pneumonias resolve without treatment. The physician knows that this will avert the small possibility of death from pneumococcal pneumonia, a formerly life-threatening disease that is now treatable.