Screening and early diagnosis: what is the difference?

The World Health Organization (1) defined the two approaches of early case detection (or finding): early diagnosis, that is the recognition of symptomatic disease in patients; and screening, which is the identification of asymptomatic disease in an apparently healthy population.
Early diagnosis focuses on detecting symptomatic patients as early as possible, while screening consists of testing healthy individuals to identify those who are more likely to have a hidden disease before any symptoms appear (Figure 1). (2) The practice of early detection and treatment during early stages of illness prevents progression of many diseases and can even be life-saving. It also helps patients to be financially and mentally prepared. (3) Early detection whether as screening or early diagnosis are secondary preventive measures. However, it is important to remember that early detection and treatment is not always best. Such tests should be done on solid reasons of necessity. Early diagnosis is required for all disease both acute and chronic; however screening is beneficial in some diseases that have a long latency period before onset of manifestations. Raising awareness of community specially the high risk groups is a perquisite for effective early case findings. To improve early diagnosis people should be sensitized enough to consult health professionals once symptoms appear, without being delayed by any financial, logistical or psychosocial barriers; together with appropriate and rapid reaction of health staff, clear referral guidelines and availability and accessibility of diagnostic and treatment services of optimal quality. (2)