Tips For Responding to False Positives

Preventive screenings such as mammograms and PSA tests can find disease early, when it’s most treatable, and help save lives. But sometimes they can indicate the presence of disease when it’s not really there — a false positive.

False positives may lead to unnecessary follow-up tests and invasive procedures like biopsies. There’s also an emotional cost to false positives, as patients can spend weeks or longer being stressed about a disease they don’t have while awaiting further test results.

It’s important to get all the preventive screenings your healthcare providers recommend — you shouldn’t let the possibility of a false positive deter you from receiving the benefits that preventive screenings offer. What you can do is learn how to respond to false positives, so their impact on you is minimized. Let’s take a closer look at the issue of false positives and strategies for dealing with them.

What’s a False Positive Rate?

When screening for a disease, there are four possible results:

• True positive: The patient has the disease and the test correctly identified it.
• True negative: The disease is not present and the test correctly indicated that.
• False positive: The test indicated the patient has the disease, when they don’t.
• False negative: The test said the patient doesn’t have the disease, when they do.

Using statistics, the probability of these outcomes occurring can be calculated for a particular preventive screening. This gives healthcare professionals a good idea about the test’s accuracy and its false positive rate (the number of false positives divided by the total number of negative cases).

False positive rates vary greatly. Some tests have false positive rates exceeding 10 percent, while others have rates about 1 percent or less.

Why Do False Positives Occur?

There’s a wide range of reasons why false positives happen, including:

• Handling errors: Samples are mislabeled or incorrectly handled.
• Poor quality testing: Lab equipment isn’t in good working order.
• Interpretation errors: Mistakes are made when interpreting results.
• Procedural errors: Standard operating procedures aren’t followed.
• Cross-contamination: Samples are contaminated by other specimens.
• Medications: A drug that the patient is taking interferes with the test.
• Patient conditions: A medical condition that the patient has triggers a false positive.

Your healthcare provider can give you more information about a screening test’s false positive rate and the possible causes of false positives. They can also answer any questions you have.

When considering undergoing a preventive screening, it’s important to understand how often false positives occur in the test and the reasons why they happen. Knowing this beforehand will help you make better decisions and possibly reduce your chances of experiencing a false positive. For example, if you are taking a medicine that can cause a false positive, discuss with your healthcare provider whether to stop taking the drug before being tested.

Tips for Responding to False Positives  

Here are some things you can do when dealing with false positives:

• Stay calm. Receiving a positive test result can be stressful and affect your sleep. The best thing to do is stay calm and remember that it may be a false positive. Don’t make any rash decisions based on initial test results.
• Seek support, if needed. If you have significant anxiety about test results, seek support from family members, friends, or a mental health professional. Blue Cross Vermont members have access to mental health telemedicine support.        
• Contact your provider. Always discuss test results with your healthcare provider. Ask questions about the possibility of a false positive, and if you suspect it could be the case, delve deeper into the situation.
• Review your medical history: Make sure your provider knows your complete medical history, including any medications (both prescription and over the counter) and supplements you are taking. Talk with your provider about whether a medication or a health condition may have caused a false positive.
• Investigate other possibilities: Explore possible causes such as technical problems or interpretation errors with your provider. Ask if there is a way to prevent them. For example, using a radiologist who is more experienced at reading mammograms can reduce the false positive rate, as their interpretation of the images may be more accurate.
• Consider retesting. Discuss with your provider repeating the test, after you’ve been able to eliminate potential error sources (i.e., stop taking a medication temporarily or waiting for a short-term condition to go away). Your healthcare provider may recommend a different testing method or using another lab for the repeat test.
• Look for more accurate alternative tests. There may be other tests with lower false positive rates that you can use to verify or disprove the original test’s results. For example, the Prostate Health Index (PHI) and PCA3 urine tests are newer and more accurate screenings for prostate cancer. If you have an elevated prostate specific antigen level on a PSA test, you may want to get one of these other tests done before resorting to a prostate biopsy.

Don’t Be Discouraged

Even though they’re not perfect, preventive screening tests can help you find disease at an early stage when treatments are most effective. Remember, a test with a 10 percent false positive rate can still identify about 90 percent of the people who have the disease.

We encourage you to get all the preventive screenings recommended by your healthcare providers and don’t be discouraged by the possibility of a false positive. Using the tips we’ve provided, you’ll be able to effectively respond to false positives and can continue on the true path to better health.  

For more information about preventive screening, check out our blog article on 12 common preventive services.