[Phases to determine the clinical utility of diagnostic tests]

In general, diagnostic tests are the necessary tools to determine the presence or absence of illness, but they can be useful also for excluding other differential conditions, assessing severity, establishing specific treatments, and estimating possible prognosis results. In order to determine how much a new diagnostic test can contribute in the clinical setting, studies with different research designs and populations are required. Since it might be complex to understand the development process of a diagnostic test based on its initial stages, this article synthesizes and gives examples of the four phases that have been proposed to define this process. The goals of these four phases are: phase I, establishing reference values; phase II, analyzing the validity of the test; phase III, the impact of its incorporation in diagnostic-therapeutic plans; and phase IV, a long-term assessment after incorporating the diagnostic test.