ABSTRACT
Epidemiology is the study of issues relating to health and health care in a population context. Statistical issues are of fundamental importance in all branches of epidemiology. One important area of epidemiology concerns the performance of screening tests and diagnostic tests. The aim is to characterise the relationship between an approximate test procedure T and a gold standard criterion G which is used to define which patients do and which do not have the disease of interest-in other words, the actual final diagnosis. Familiar and widely studied examples include the use of mammography to screen women for breast carcinoma and prostate specific antigen (PSA) measurement to detect prostate cancer in men. In general, both T and G may be single-test procedures or more complex algorithms.
