Ground Truth Strategy
<Early draft - comments and input welcome>
It's worthwhile starting to think about the ground truth strategy for the Profile early in the process. As shown below, the choices may affect a variety of profiling activities so working through it early makes those subsequent activities easier to plan. Also, challenges obtaining ground truth can become a roadblock to profile progress. Understanding the situation early allows lead time to find and recruit resources for collecting such data (such as clinical trials with common interests, or at least common methods).
Approaches to consider may include:
- Gold Standard
- using another method that is widely-accepted as definitive to make measurements that will serve as the ground truth for biomarker assessments
- Reference Standard
- using another method that may not be definitive but has known measurement performance or serves as a stable benchmark
- using two measurements on the same subject to "sidestep" bias and focus on repeatability
- Pocket Phantom
- using measurement of an object with known ground truth in concert with biomarker measurements
Practical and scientific issues will differ from biomarker to biomarker. The use of ionizing radiation or injected imaging agents may prevent or limit the ability to perform test-retest studies. The ability to measure the property underlying the biomarker using other methods and the equivalence between those methods and the biomarker (or lack thereof) may limit the use of Gold Standards or Reference Standards.
Places where the ground truth strategy may come into play include:
- the strategy might help define study methods and data collected during initial groundwork to assess current performance and sources of variation
- the strategy must address the performance metrics chosen in the Claims
- if no practical strategy is available, it may be necessary to make different claims
- the strategy might manifest in a site assessment procedure
- the strategy might form the basis of the Claim Confirmation and Clinical Confirmation processes
The Metrology Committee may be able to provide tailored advice. Feel free to consult them.