The introduction of p-tau217 blood biomarker testing by Quest Diagnostics directly impacts the company by potentially increasing its market share in the diagnostic testing market, especially for Alzheimer's Disease. This new service could lead to higher demand for Quest's testing services, given the growing need for early detection and management of Alzheimer's. The positive impact on DGX's stock price in the short term is likely due to the anticipated increase in demand for these new testing services.