Screening tests are designed to detect treatable conditions before symptoms appear, potentially preventing premature disability or death. However, the direct-to-consumer testing industry increasingly promotes tests that promise reassurance but often deliver ambiguous findings, leading to expensive follow-ups and unnecessary anxiety.
What Is Medical Screening?
Screening involves medical testing for conditions in asymptomatic individuals. Effective screenings, like blood sugar tests and blood pressure checks, identify diseases with long asymptomatic periods—such as diabetes and hypertension—that can cause damage to eyes, kidneys, brain, and heart for years before symptoms emerge. Early detection allows for interventions like diet, exercise, and safe medications that stop disease progression. These tests are cheap, easy, and far more beneficial than harmful.
The Problem with Overscreening
While knowledge is power, more testing is not always better. Experts use the term "overscreening" to describe excessive testing that uncovers untreatable or insignificant findings, prompting additional costly and potentially harmful interventions with unclear benefits. Full-body MRI scans exemplify this. Popularized by techno-optimists and celebrities, they are marketed as proactive ways to detect "silent killers" like aneurysms and tumors. However, MRI technology often identifies "incidentalomas"—tiny cysts, nodules, or anatomical quirks of unclear significance. A review of whole-body MRI studies found that 95% of participants had abnormal findings, about a third required further investigation, and fewer than 0.5% were suspicious for cancer.
"Humans are full of abnormality, particularly as they age," says Gilbert Welch, a researcher of overdiagnosis at Brigham and Women's Hospital in Boston. Many findings are irrelevant, but clinicians often act on all of them because they cannot distinguish which are harmless.
Harms of Overscreening
Incidentalomas are unlikely to cause harm but trigger cascades of additional testing, biopsies, and specialist visits, costing time and money and causing discomfort and medical complications. Even established tests can be overused. For example, experts debate the optimal frequency of screening mammograms for low-risk women. Long-term data suggest more frequent mammography significantly increases breast cancer diagnoses, especially early-stage disease, but leads to much smaller reductions in advanced cancer, and effects on overall mortality are uncertain. A large share of detected cancers may never progress. For older patients, frequent screening may increase the risk of unnecessary invasive procedures.
Overscreening also creates worry and a sense of ill health. Suzanne O'Sullivan, a neurologist at London's National Hospital for Neurology and Neurosurgery, notes that before a hypothetical screening MRI, you might feel healthy. After a finding of uncertain significance, "I won't feel healthy any longer." She adds that elaborate screening might be more useful when disease progression is better understood. Meanwhile, "someone's making an awful lot of money pretending to keep people healthy."
When Screening Is Appropriate
For people with certain family and medical histories, experts recommend earlier and more frequent tests. For instance, those with a close relative with colorectal cancer should have earlier and more frequent colonoscopies. Most primary care clinicians use evidence-based guidance to recommend appropriate screenings at different life stages and can serve as a resource before purchasing direct-to-consumer (DTC) tests.
Questions to Ask Before a Screening Test
The FDA does not review all DTC tests, and independent evaluations of accuracy and usefulness are hard to find. Before buying a test, ask the seller: Does this test reduce deaths or disability, or just increase diagnoses? How often does it produce false positives or overdiagnosis? Is treatment for what it finds safer than leaving it alone?
Ultimately, Welch says the path to health involves "things your grandmother might have told you: eat your fruits and vegetables, go play outside," and find meaningful activity and connection. "We're teaching the next generation the path to health is by collecting data on yourself," he warns, but "you can't test yourself to health."
