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How False Positives Work (and What They Could Mean for Your Health)


How False Positives Occur
Grace Lee, M.R.T. (R) performs a mammogram on Sharon Panke, at the Ontario Breast Screening Program in Toronto, 2005.
Grace Lee, M.R.T. (R) performs a mammogram on Sharon Panke, at the Ontario Breast Screening Program in Toronto, 2005.
Tannis Toohey/Toronto Star via Getty Images

Unfortunately, it's difficult to eliminate false positive test results. For example, a mammogram may show abnormal cells in the breast ducts that could become cancerous, but in actuality they are not life-threatening and won't cause symptoms [source: National Cancer Institute]. Patients screening for ovarian cancer may be given a cancer antigen 125 blood test (CA-125). If a woman's CA-125 level is elevated, cancer is suspected and additional testing may result. The problem is, a lot of other conditions can cause an elevated CA-125 level, such as diverticulitis, pregnancy and even normal menstruation [source: Laughlin-Tommaso].

Of course, if one test seems to suggest you might have cancer, more have to be performed to be sure. And all of this drives up health care costs. Scientists studied 1,087 people participating in screening trials for ovarian, lung, prostate and colorectal cancers and published their findings in the December 2004 issue of Cancer Epidemiology, Biomarkers & Prevention. More than 40 percent of participants had at least one false positive test result; 83 percent of them subsequently received additional care because of this. The price tag? Female patients incurred an extra $1,024 in medical charges, while males hit $1,171 [source: Lefata]. Since this study was conducted 11 years ago, the fees would be much higher today. A 2015 study put the collective cost for false positive mammograms and breast cancer overdiagnoses at $4 billion a year.

Many would argue a far greater cost is in personal angst. A Danish study, published in a 2013 issue of the Annals of Family Medicine found women who received a false positive mammogram suffered from anxiety and depression up to three years after the faulty diagnosis — long after they knew they did not have breast cancer. Many women also had problems with sleeping and with their sex lives [source: Moisse].

So once again, no one is suggesting scrapping these tests, which save many lives. The take-away is to do your homework. Work closely with your medical professional to determine which tests are in your best interest, and how frequently you should have them done. And try not to become too alarmed if you receive a positive test result. It might be inaccurate.


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