A $30,000 drug. A $1,000 test. Guess which one insurance covers?

For the modern physician, the promise of precision medicine is often more of a tease than a reality. We are told we are entering an era of "targeted therapies," yet at the bedside, the tools required to hit those targets remain frustratingly out reach. A new analysis from the University of California, San Francisco (UCSF), published in Science, confirms what many clinicians have long suspected: diagnostics are being overlooked, creating a "diagnostic gap" that threatens to undermine the last decade of pharmaceutical advancement.

Without the right tests, even the most innovative medicines make no difference. As therapies outpace the development of the tests needed to guide them, physicians are increasingly left to make critical medical decisions with inadequate information, or worse, no information at all.

The point-of-care reality

The gap between scientific potential and clinical reality is most visible during a standard patient encounter. Kathryn Phillips, PhD, lead author of the study and professor of health economics at UCSF, notes that the deficit isn't always a matter of missing technology, but of missing access.

“Most people can easily understand how a new drug or surgery might help a patient,” Phillips says. “But the tests that guide medical decisions are just as critical.”

When asked how this gap manifests for the practicing physician, she points to the administrative and logistical hurdles that clutter the workflow. “Sometimes it’s because there are no tests available, but sometimes it’s because physicians don’t have access to them. Getting the right test may involve a separate lab visit that has to be coordinated prior to the visit with the physician, or the test may not be covered by insurance,” she says.

The $30,000 disconnect: The case of Alzheimer’s

Perhaps no clinical scenario illustrates this gap more starkly than the current state of Alzheimer’s disease management. We now have access to novel drugs designed to slow disease progression, therapies that can cost upwards of $30,000 per year. These drugs frequently qualify for insurance coverage. However, the blood tests essential for matching patients to these specific treatments — tests that cost approximately $1,000 — rarely receive the same coverage.

This creates a paradoxical clinical environment where the "gatekeeper" tool is harder to acquire than the treatment itself.

“It’s often the case that the needed test costs a lot less than the drug or intervention, but it can be hard to target testing to the right people,” says Phillips. “If everyone age 50 and above thought that they wanted the blood test for AD [Alzheimer’s Disease], that would cost a lot.”

The result is a system where insurers, fearing the aggregate cost of mass testing, create barriers that leave neurologists and primary care doctors to manage patients without necessary information.

Beyond Alzheimer’s: The GLP-1 and rare disease crisis

The diagnostic deficit is not limited to neurology. In the burgeoning field of metabolic health, GLP-1 drugs for obesity and diabetes have seen a massive surge in utilization. Yet, clinicians are flying blind; currently, few tests exist to predict which patients will actually benefit from these expensive treatments and which will not respond.

Furthermore, the "diagnostic odyssey" remains a grim reality for those treating rare diseases. These conditions often take many years to diagnose, a delay that is increasingly unacceptable as gene therapies and other precision interventions become available. When the therapy exists but the diagnostic path is obscured by policy or payment gaps, the "precision" in precision medicine becomes a misnomer.

A systemic misalignment

Why is the diagnostic landscape so barren compared to the pharmaceutical one? The UCSF analysis points to a deep-seated systemic misalignment in how we value, regulate, and pay for medical tools.

1. Regulatory Silos: The FDA reviews diagnostic tests and drugs through entirely different tracks, with drugs far more likely to receive expedited review status. This means a drug may reach the market long before the companion diagnostic needed to use it safely or effectively is ready.

2. The Reimbursement Gap: Insurers generally treat diagnostics with more skepticism than therapeutics, providing less investment for research and lower reimbursement rates. Robert M. Califf, M.D., former FDA commissioner and study co-author, notes that this leaves "powerful tools on the shelf" because there is inadequate data to determine which tools provide real-world benefits.

3. Fragmented Care: Because diagnostics are handled separately from treatments, they are often treated as an optional add-on rather than a core component of the therapeutic process.

Closing the gap: A path forward for physicians

The UCSF authors argue that policymakers must evolve in tandem with scientific advances. Key recommendations include reviewing tests and treatments together, streamlining approvals for tests, and improving how diagnostics are evaluated so their role in preventing ineffective treatment — and the associated costs — is properly valued.

For the individual physician feeling powerless against these systemic issues,Phillips’ message is simple: “Stay informed.” The shift toward recognizing diagnostics as essential will require clinical advocacy and a change in how we perceive the tools in the diagnostic kit.

“Our hope is that this work helps people — patients, policymakers, insurers, and researchers — recognize diagnostics as essential to good health care — and not just an afterthought,” says Phillips. Until this "diagnostic deficit" is closed, the true potential of precision medicine will remain a luxury that many patients — and the health care systems — simply cannot afford.