Methods and limitations of assessing new noninvasive tests - Part II: Outcomes-based validation and reliability assessment of noninvasive testing

Outcomes-based approaches are the preferred methodology for technology validation. As discussed in part I of this review, the difficulties of performing an unbiased diagnostic evaluation are increasingly appreciated. 1 An outcomes-based approach is advantageous in that it mimics the clinical application of testing. By risk stratifying patients, the results of this approach can be applied directly to clinical practice. 2 Nonetheless, outcomes-based technology validation is not without challenges and limitations. These issues include the need for multivariable modeling for observational data, end point selection, and limitations of estimating posttest risk. Finally, it is increasingly appreciated that the future "gold standard" for outcomes-based assessments will be demonstrating whether imaging can identify which therapeutic approach optimizes patient benefit rather than merely identifying risk.