Am Fam Physician. 1999;59(10):2714-2715
False-positive screening tests are common and can be emotionally devastating to patients. Unfortunately, many patients are not aware that the vast majority of positive screening tests occur in completely healthy persons. In the case of fecal occult blood testing, for instance, about 50 positive tests are obtained for every one case of colon cancer identified, and four positive tests are obtained for every polyp that is found.1 About 2,000 abnormal Papanicolaou (Pap) smears occur for every case of cervical cancer discovered, and around 10 abnormal Pap tests occur for every case of intraepithelial neoplasia detected.2 Twelve abnormal mammograms and three or more biopsies are performed before one case of breast cancer is found.3 High false-positive rates also occur in screening programs for pre-natal and neonatal diseases, such as spina bifida, trisomy 21 and phenylketonuria.
Nonetheless, many patients misinterpret a positive screening test as proof of some dreaded hidden disease. Not infrequently, this experience results in severe, sustained and potentially disabling anxiety in the patient or the family. The level of anxiety has been compared with the anticipation of major surgery and can occasionally rival that experienced in panic attacks.4 Once established, the anxiety typically persists until definitive testing is completed and good health reconfirmed.
Patients should not have to suffer because of our inability to devise more specific screening tests. Although few good interventional studies have been conducted, the literature suggests several prudent measures that can be performed to minimize anxiety. The most obvious but perhaps neglected intervention is informing patients—before screening—that many positive results are found to be errors. Simply understanding this up front could save many patients a lot of worry.
In addition, patients should be informed of positive results face-to-face to minimize inevitable misunderstandings.5 If such a meeting cannot be arranged, then a personal telephone call is appropriate. Letters informing patients of a positive screening test result should only be used as a last resort, and no patient should receive such a letter on a weekend when he or she would be unable to contact the physician who sent it. If letters must be used to relay the news of a positive test result, reassuring language should be used, and it is helpful to include an informational brochure that discusses the likely benign nature of the positive result.6 Notification letters from public or private organizations that conduct screening tests are doubly problematic because of their anonymity and their air of authority. State newborn screening laboratories, blood banks and insurance companies should all be encouraged to release sensitive screening test results through the patient's physician.
Finally, follow-up testing must be completed as quickly as possible. A normal definitive test usually brings definitive relief. Tests that leave room for doubt about the patient's condition are less effective at reducing anxiety.4 Unfortunately, even after normal definitive studies have been completed, some patients are not completely reassured and continue to worry.7 Risk factors for protracted emotional problems include having little formal education, and the presence and continuation of symptoms in the organ system screened.
Only infrequently does a positive screening test mean significant disease. Most of the time, the test triggers only a routine recall. The challenge is to make it routine from the patient's point of view.