DECISION ANALYTIC GUIDANCE OF DIAGNOSTIC TEST EVALUATION OBVIATES THE REQUIREMENT FOR RANDOMIZED TRIALS

Purpose: Along with the need for outcome and cost information in order to determine the value of diagnostic tests and imaging procedures has come confusion about the research required...……including the conclusion by some that randomized clinical trial are essential.   We sought to clarify the data needed and the optimal sequence of steps in the evaluation of diagnostic tests and procedures.

Method(s): A decision analytic model is used to analyze the clinical scenario in which a new diagnostic test is used and then solved to determine the information needed to decide if its use could be an optimal strategy compared to the existing diagnostic strategy.  When the major determinate is its incremental accuracy, a challenge region is plotted in ROC space to specify how accurate the test would have to be in order for it to be a cost effective alternative to the current diagnostic strategy.

Result(s): Before accuracy, the optimal sequence is to evaluate the diagnostic modality's feasibility, reliability, and diagnostic yield.  If these are encouraging, the next step is a prospective cohort study comparing the accuracy of new test A to existing test B.   The impact of the test on outcomes can then be estimated using available information about the other variables needed to populate the model.  Again, if this indicates that the test is potentially better and cost-effective, then the information about the diagnostic test's accuracy should be provided to clinicians in “real life” situations to evaluate whether, and to what extent, its results actually influence decision-making.  The cost-effectiveness of the diagnostic test can subsequently be projected from the decision analytic model.

Conclusion(s): The use of decision analysis can guide the efficient evaluation of diagnostic tests.   The determination of accuracy is a prerequisite for studies to evaluate the impact, outcomes and cost effectiveness of its use, potentially obviating the need for RCTs.