When a tailored therapy and the companion diagnostic tool are not developed concurrently, a Laboratory Developed Test (LDT) may be used to identify patients in the pivotal clinical trial (CT). Upon subsequent development of a regulatory required validated In-Vitro Diagnostic (IVD), CT samples need to be re-tested. Where insufficient samples are available for retesting of all patients, a bridging study is needed to evaluating the agreement between the LDT and IVD. In an oncology drug and diagnostic tool submission, we applied statistical methods (including an analytic approach as well as multiple imputation) to estimate drug efficacy in the IVD-defined target population (IVDTP). This enables a more informative approach to bridging from an LDT to an IVD than measures of agreement alone.