Ⅰ.DIAGNOSTIC UNCERTAINTYrnWe always face diagnostic uncertainty.Decision making,by means of diagnostic tests,is a major task to clinicians,especially in critical patients.Take an example.A man comes with chest pain at 2 am.The gold standard of cardiac catheterization to see if there is any occlusion of coronary arteries,remains the best option.However it is invasive.Cardiologists and laboratory support may not be available.But minutes count.We may want to have a reliable diagnostic test to rule in or rule out myocardial infarct.