<p>Precision medicine (PM) promises better outcomes by aligning prevention and treatment with molecular and phenotypic profiles. But precision is not merely a clinical refinement; it is an epistemic shift in how health systems classify risk, allocate eligibility and define value. In this study, we argue that broad adoption of PM creates structural tension within solidarity-based health systems and exposes limits in conventional cost-effectiveness evaluation. Ethically, PM converts pooled probabilistic uncertainty into individualized biological prediction, making access increasingly conditional on measurement, interpretation and pathway completion. Economically, PM fragments evaluable populations, destabilizes counterfactual comparison and shifts value from discrete products to information-dependent care pathways. As a result, standard metrics such as the incremental cost-effectiveness ratio (ICER) often become sensitive not only to biological effect, but also to governance: who is tested, how results are interpreted, which downstream services are funded and who can complete the pathway. We suggest that the instability observed in PM appraisal is not simply a technical problem of modeling, but a sign that the object of evaluation has changed. Recognizing this structural shift is essential if PM is to be integrated into health systems committed to both equity and evaluability.</p>