Without the Right Tests, the Best Medicines Make No Difference

A new analysis from UC San Francisco argues that diagnostics — medical tests that match patients to the appropriate treatment — are being overlooked both in the United States and around the world. This is slowing progress against major diseases, despite rapid advances in targeted therapies and precision health.

The authors noted that nearly half of the world’s population lacks adequate access to diagnostics. These tests receive less investment for research and development, as well as lower insurance reimbursement than drugs; and this is creating barriers to innovation.

“Most people can easily understand how a new drug or surgery might help a patient,” said Kathryn Phillips, PhD, a professor of Health Economics in the School of Pharmacy at UC San Francisco and the lead author of the study, which appeared in Science on April 9. “But the tests that guide medical decisions are just as critical.”

Advances in therapies are outpacing the development of the tests that are needed to guide their use. For example, many people do not respond to GLP-1 drugs for obesity and diabetes, but few tests exist yet to predict which patients will benefit.

Alzheimer’s is another example. New drugs exist to slow disease progression, but the blood tests that could match patients to the most beneficial drugs cost around $1,000 and — unlike the drugs, which cost $30,000 a year — they rarely qualify for insurance coverage. This can leave doctors to make medical decisions without the necessary information. Some patients may not get the right treatments, and others may not get any treatments.

Even though they are essential to care, these diagnostic tests are often handled apart from the treatments they support. The FDA reviews tests differently than drugs, and insurers pay for them differently. Drugs are also much more likely to receive expedited FDA review than tests.

“Regulatory and payment policy should evolve in tandem with scientific and technological advances,” said Robert M. Califf, MD, former commissioner of the U.S. Food and Drug Administration and co-author of the paper. “The current misalignment between how we evaluate diagnostics for consideration of allowing marketing and the system for reimbursement decisions about diagnostics versus drugs leaves powerful tools on the shelf and provides inadequate data to make good decisions about which diagnostic tools should be eschewed for lack of benefit in the real world."

The authors say there are clear steps policymakers can take to fix these gaps, including reviewing tests and treatments together, streamlining approvals for tests, and improving how diagnostics are evaluated and paid for.

“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,” said Phillips, who  directs the UCSF Center for Translational and Policy Research on Precision Medicine (TRANSPERS) and is a member of the Philip R. Lee Institute for Health Policy at UCSF.

Reference: Phillips KA, Horn DM, Califf RM. Diagnostics investments and disease burden. Science. 2026;392(6794):151-153. doi: 10.1126/science.aec0173

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