GH stock surged 226% in 2025, making it the best performing healthcare stock of the year. But the stock price is not the story. The story is why fifty million Americans refuse to get screened for a cancer that kills more people than car accidents. Colorectal cancer is the second leading cause of cancer death in the United States. Most cases are preventable with early detection. Yet 41% of eligible adults never complete a screening. They skip the colonoscopy because it requires sedation, fasting, and a full day off work. They avoid the stool test because it feels invasive and unpleasant. So they defer, delay, and eventually die from a disease that could have been caught early. Guardant Health built a blood test called Shield. One tube drawn at a routine doctor visit. No prep. No sedation. No disruption. And it detects colorectal cancer with 83% sensitivity. The barrier to screening was never technology. It was behavior. Guardant solved the behavior problem.
The Compliance Curve: Why Friction Kills
The clinical data tells a surprising story. Colonoscopies detect cancer with over 90% sensitivity, which is better than Shield's 83%. But sensitivity only matters if people actually complete the test. Since Shield launched commercially, more than 90% of patients who receive a prescription complete it. Compare that to colonoscopy completion rates, which range from 28% to 71% depending on the study. The gap is not clinical. It is behavioral. A colonoscopy requires scheduling weeks in advance, arranging transportation, taking time off work, and enduring an uncomfortable prep. Shield requires showing up for a routine appointment and offering your arm. For the millions who would never screen otherwise, 83% detection beats zero. Medicare understood this trade-off. CMS granted Shield premium reimbursement at $1,495 per test, signaling that removing friction may save more lives than optimizing sensitivity.
The Hidden Catalyst: From Available to Mandated
Most investors track Medicare coverage because that is where the headlines appear. But Medicare serves 45 million beneficiaries. The real unlock is the under-65 population, which includes 180 million American adults. The U.S. Preventive Services Task Force sets the standard of care for cancer screening. Once Shield receives an A or B rating alongside colonoscopy, private insurers become legally required to cover it under the Affordable Care Act. Zero copay. Zero deductible. For every working-age American with insurance. USPSTF guidelines update in 2026. If Shield makes the list, the addressable market does not grow. It becomes legally accessible. That transition from available to mandated is the catalyst Wall Street has not fully priced.
The Dual Engine: Screening Plus Oncology
Shield grabs the headlines, but Guardant is not a single-product company. The oncology business generated $541 million in 2024 from Guardant360 liquid biopsies, which help oncologists select targeted therapies for cancer patients. That segment grew 40% in volume for five consecutive quarters. Together, screening and oncology address an estimated $80 billion liquid biopsy market. Shield is the growth engine. Guardant360 is the cash engine. The combination creates a platform that competitors cannot replicate with a single product launch.
The competitive moat is not the blood test itself. It is the compliance curve that the blood test unlocks. Shield reaches the fifty million Americans who refuse every other option. Quest Diagnostics will distribute it nationally starting in 2026. TRICARE now covers it for military families. The infrastructure for scale is building. The investors who understand Guardant are not betting on a diagnostic. They are betting that convenience beats clinical perfection when the alternative is no screening at all. Every tube of blood drawn is one more American who did not skip the test. Every percentage point of compliance gained is lives saved. The innovation was not finding the cancer. It was finding the patient.