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Group sequential testing procedures have been proposed as an approach to conserving resources in biomarker validation studies. Previously, we derived the asymptotic properties of the sequential empirical positive predictive value (PPV) and negative predictive value (NPV) curves, which summarize the predictive accuracy of a continuous marker, under case‐control sampling. A limitation of this approach...
Many biomarkers identified in marker discovery are shown to have inadequate performance in validation studies. This motivates the use of group sequential designs that allow early termination for futility. However, an option for early termination will lead to biased estimates for studies that reach full enrollment. We propose conditional estimators and confidence intervals that correct for this bias...
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