ABSTRACT
Diagnosis is an extremely important part of medical practice. Proper diagnosis help determine the best course of treatment. A biomarker is a numerical outcome that is based on a measurement of a biological substance that is associated with a particular disease or infection. This chapter deals with binary diagnostic tests under a variety of circumstances. It deals with biomarkers that are regarded as continuous. The chapter discusses what are called receiver operating characteristic (ROC) curves. Investigators use ROC curves to determine where to place the threshold for declaring the presence or absence of a condition. The chapter shows how diagnosis can be accomplished using the biomarkers without the use of arbitrary cutoff values as in the traditional way. It discusses ROC regression in which covariate information can be used to help with diagnosis in various ways.
