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Published on: June 10, 2025
Conditional estimation of sensitivity and specificity from a phase 2 biomarker study allowing early termination for
Margaret Sullivan Pepe1, Ziding Feng, Gary Longton
1Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N., M2-B500, Seattle, WA 98109, U.S.A. mspepe@u.washington.edu
Abstract:
Development of a disease screening biomarker involves several phases. In phase 2 its sensitivity and specificity is compared with established thresholds for minimally acceptable performance. Since we anticipate that most candidate markers will not prove to be useful and availability of specimens and funding is limited, early termination of a study is appropriate, if accumulating data indicate that the marker is inadequate. Yet, for markers that complete phase 2, we seek estimates of sensitivity and specificity to proceed with the design of subsequent phase 3 studies. We suggest early stopping criteria and estimation procedures that adjust for bias caused by the early termination option. An important aspect of our approach is to focus on properties of estimates conditional on reaching full study enrollment. We propose the conditional-UMVUE and contrast it with other estimates, including naïve estimators, the well-studied unconditional-UMVUE and the mean and median Whitehead-adjusted estimators. The conditional-UMVUE appears to be a very good choice.
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