<unk> can detect medical conditions at an early stage before symptoms present while treatment is more effective than for later detection. In the best of cases lives are saved. Like any medical test, the tests used in<unk> are not perfect. The test result may incorrectly show positive for those without disease (false positive), or negative for people who have the condition (false negative). Limitations of<unk> programmes can include: *<unk> can involve cost and use of medical resources on a majority of people who do not need treatment. * Adverse effects of<unk> procedure (e.g. stress and anxiety, discomfort, radiation exposure, chemical exposure). * Stress and anxiety caused by prolonging knowledge of an illness without any improvement in outcome. This problem is referred to as overdiagnosis (see also below). * Stress and anxiety caused by a false positive<unk> result. * Unnecessary investigation and treatment of false positive results (namely misdiagnosis with Type I error). * A false sense of security caused by false negatives, which may delay final diagnosis (namely misdiagnosis with Type II error).<unk> for dementia in the English NHS is controversial because it could cause undue anxiety in patients and support services would be stretched. A GP reported "The main issue really seems to be centred around what the consequences of a such a diagnosis is and what is actually available to help patients."
Screening 
Immunity passport
Risk panel
Disease surveillance
Nutritional rating systems
Cancer screening
Risk assessment
Public health surveillance