Understanding False Positives in Cancer Screening Tests

Medically reviewed by Jillian Foglesong Stabile, MD, FAAFP, DABOM on March 19, 2026. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

What Are Cancer Screening Tests?

Cancer screening tests are designed to detect cancer or precancerous changes at an early stage—before symptoms develop.[1] Early detection can improve survival rates, expand treatment options, and potentially reduce the cost of care.

Cancer screening tests are available for many types of cancer, including:

• Breast cancer: Mammogram
• Colon cancer: Colonoscopy, stool-based tests
• Cervical cancer: Pap smear, HPV testing
• Lung cancer: Low-dose CT scans
• Other cancers: Certain blood-based tests may detect signals associated with cancer

Not all tests are appropriate for screening, and not all cancers have effective screening options. A good screening test typically meets several criteria:[1]

• Detects cancer or precancerous cells before symptoms appear
• Identifies cancer at an early, more treatable stage
• Improves outcomes when detected early
• Maintains a balance of accuracy with low false-positive and false-negative rates

It’s important to remember that screening tests do not diagnose cancer—they identify whether further testing is needed. Screening recommendations are often personalized based on your age, medical history, family history, and risk factors.

Understanding False Positives

A false positive occurs when a test suggests a condition may be present, but follow-up testing confirms that it is not. In cancer screening, this means a test may indicate possible cancer or precancer, even though no cancer is ultimately found.[2]

False positives are one reason follow-up testing is essential after an abnormal result. While screening tests aim to be as accurate as possible, no test is perfect.

The likelihood of false positives can vary depending on:

• The type of screening test
• The population being tested
• The frequency of screening

Healthcare providers weigh these factors carefully when recommending screening options.

Why Do False Positives Happen?

False positives can occur for several reasons. One key factor is that screening tests are designed to be highly sensitive—meaning they aim to detect as many potential cases as possible.[2]

While this sensitivity helps catch cancer early, it can also identify non-cancerous changes that appear abnormal.

Other contributing factors include:

• Natural biological differences between individuals
• Benign (non-cancerous) conditions that resemble cancer
• Technical or processing errors
• Human interpretation variability

Additionally, when large populations are screened—especially for rare conditions—even a small error rate can result in a higher number of false positives.[3]

Screening always involves a balance between sensitivity (catching true cases) and specificity (avoiding false positives). Your healthcare provider considers this balance when recommending tests.

What Are the Consequences of False Positives?

False positive results can have several impacts, both emotional and physical.

• Emotional impact: Anxiety, stress, and uncertainty while awaiting follow-up results
• Additional testing: Repeat tests, imaging, or biopsies that may be invasive
• Physical risks: Potential discomfort, complications, or side effects from procedures
• Financial impact: Increased healthcare costs for individuals and the system

In some cases, false positives may also affect a person’s willingness to participate in future screening.[4]

How Are False Positives Addressed?

If you receive a positive screening result, the next step is to follow up with your healthcare provider. They can guide you through additional testing to determine whether cancer is actually present.

Screening methods continue to evolve, with ongoing improvements aimed at increasing accuracy and reducing unnecessary follow-up testing.

Guidelines are regularly updated to ensure that screening is recommended for the right populations at the right time—helping balance benefits with potential risks like false positives.

Learn More About Cancer Screening Options with Everlywell

Want to better understand your cancer screening options? Everlywell offers tools designed to support early detection and informed decision-making.

The Galleri® Multi-Cancer Early Detection Test is a cancer screening test that can detect signals associated with more than 50 types of cancer—often before symptoms appear. We also offer fecal immunochemical testing (FIT) for colon cancer screening.

These options can help you take a more proactive approach to your health, alongside guidance from your healthcare provider.

References

1. Cancer screening overview. Cancer.gov. Published October 20, 2023. Accessed February 10, 2026. https://www.cancer.gov/about-cancer/screening/patient-screening-overview-pdq
2. Shreffler J, Huecker MR. Diagnostic testing accuracy: sensitivity, specificity, predictive values and likelihood ratios. StatPearls. Published March 6, 2023. Accessed February 10, 2026. https://www.ncbi.nlm.nih.gov/books/NBK557491/
3. White T, Algeri S. Estimating the lifetime risk of a false positive screening test result. PLoS ONE. 2023;18(2):e0281153. doi:10.1371/journal.pone.0281153
4. Mammogram false positives affect future screening behavior. Cancer.gov. Published October 4, 2024. Accessed February 10, 2026. https://www.cancer.gov/news-events/cancer-currents-blog/2024/mammogram-false-positives-affect-future-screening
5. Madhavan S, Hackshaw A, Hubbell E, et al. Estimating the burden of false positives and implementation costs. Cancer Medicine. 2025;14(6):e70776. doi:10.1002/cam4.7077