Systematic Review: The Long-Term Effects of False-Positive Mammograms

Context Do false-positive mammograms affect women's well-being and behavior? Contribution This systematic review summarizes data from 23 observational studies that compared outcomes after false-positive results or normal results on screening mammograms. Women who received false-positive results had slightly higher levels of distress and more thoughts about cancer several months after screening than women who received normal results. They also performed breast self-examinations more frequently and, in the United States, were slightly more likely to return for repeated routine screening examinations (risk ratio, 1.07 [95% CI, 1.02 to 1.12]). Implication False-positive mammograms may have persistent small effects on some women's psychological well-being and behavior. The Editors Regular mammography has become part of routine health care in the developed world for women 40 years of age or older. Routine mammography is important because it reduces death due to breast cancer by detecting tumors early (13). Unfortunately, many women receive false-positive results on screening tests. In the United States, approximately 11% of screening mammograms lead to false-positive results, which can cause women to incur substantial personal and financial costs related to follow-up testing (4, 5). One study (6) estimated that increased medical care use related to false-positive results on mammography costs $100 million per year in the United States. Researchers have shown that false-positive results negatively influence women's psychological well-being during the period immediately surrounding tests (7). Although researchers have performed several studies (79) on the effect of false-positive mammograms on women, the long-term effect is poorly understood. Women who receive false-positive mammograms may be discouraged from further routine screening mammographies (10). Testing errors could undermine women's confidence in the benefit of mammography and in the medical system's ability to provide adequate care, making them less likely to return for routine mammography. The costly and time-consuming follow-up procedures prompted by false-positive results may be an additional disincentive for return. Alternatively, false-positive mammograms may not have a negative effect on subsequent screening mammographies. Only one half of women with abnormal mammograms are aware of having received false-positive results (11). A recent survey in the United States found that of the adults who recall having received false-positive results on screenings for cancer (including mammographies), 98% were still glad that they had had the tests performed (12, 13). Women are concerned about receiving overdiagnosis and overtreatment but not about receiving false-positive results per se (14). A final and less commonly argued alternative is that false-positive results might actually increase routine screening because they increase anxiety, worry, and perceived risk (7, 1520). Anxiety, in turn, may cause women who receive false-positive results to be more vigilant about early detection than women who receive normal results. Although extreme anxiety caused by screening seems to be rare, abnormal mammograms apparently prompted 2 British women to commit suicide (21). Many studies have addressed the long-term consequences for women who receive false-positive mammograms, but these studies have yielded contradictory results, with different studies supporting each of the 3 possibilities described. Other reviews (7, 9, 18, 2225) emphasized short-term psychological consequences, largely ignored health behaviors, were typically not systematic reviews, and did not screen studies for minimum quality criteria. Because mixed findings among diverse outcomes have thwarted the understanding of the presence and extent of the long-term effects of false-positive screening mammograms, we conducted a systematic review of the relevant literature. We aimed to characterize the long-term effects of false-positive screening mammograms on the behavior and well-being of women 40 years of age or older. Methods Data Sources and Searches We conducted the review by using the following protocol. Two reviewers independently searched the MEDLINE, Web of Science, EMBASE, CINAHL, PsycINFO, and ERIC databases for studies published through September 2006 whose title, abstract, or keywords included reference to both false-positive results and screening mammography. The search terms were (false positive OR abnormal OR benign) AND (breast cancer OR mammog*). We also manually searched the reference sections of relevant papers and circulated requests for unpublished studies among colleagues and the authors of the articles we identified. We limited the searches to English-language studies. Study Selection Two reviewers independently screened the titles, then abstracts, and then text of articles that seemed pertinent. We identified studies that examined the effects of false-positive mammograms on the behavior, well-being, or beliefs of women 40 years of age or older by using selection criteria that we specified before the review began, except as noted. We excluded studies that did not meet the following quality criteria. We required that initial mammography screening results (abnormal or normal) be obtained from routine mammography because mammographies conducted for reasons other than screening take place in a very different context. We excluded studies of mammography prompted by symptoms or initial screening by clinical breast examination. We required that women receiving false-positive results be compared with women from the same sample who received normal results. Unacceptable comparison groups included unscreened women and women screened at other times or in different settings. We defined false-positive results on mammograms as abnormal results that did not lead to a cancer diagnosis after follow-up mammography, ultrasonography, magnetic resonance imaging, fine-needle aspiration, or biopsy. While reviewing the studies, we decided to include 2 studies (26, 27) that did not report the resolution of abnormal screening results because very few abnormal results indicate cancer (28). The inclusion of these studies did not change our findings. We required that initial screening be real (not imagined in a hypothetical vignette) and that results be assessed from medical records or by patient self-report. Studies had to include the outcome of return for routine screening within the interval recommended in the country or health system in which the study was conducted; we did not consider mammographies that were follow-ups of abnormal results or were part of a clinical trial as routine, initial mammographies. We required that women who returned for screening be assessed from medical or registry records or by patient self-report; however, we did not include intention to be screened as an acceptable measure. Additional outcomes included behavior, well-being, and beliefs, such as self-report of conducting breast self-examinations, anxiety, worry, perceived risk, and depression. We required that these outcome measures be assessed at least 1 month after cancer was ruled out so that the data reflected long-term consequences of false-positive screening results and not immediate distress in the period between receiving an abnormal test result and the subsequent negative result for cancer. Although breast self-examination has not been shown to reduce death due to breast cancer (29), we included it in our analysis as an additional demonstration of the effect of false-positive results on women's behavior. We required that studies reported bivariate statistical analyses of original, quantitative data or reported data that could be reanalyzed, although we accepted studies that reported null effects without indicating their size or direction. In practice, we did not exclude studies that reported results only after adjustment for covariates, although we excluded several studies that reported complex analyses that did not allow us to determine the relevant main effect. Data Extraction and Quality Assessment Two investigators independently used a standardized data extraction form to code the studies on characteristics that could alter the effect of receiving a false-positive result. In addition, we coded variables that reflect study quality, such as study design and use of self-report. During our review process, we refined our coding criteria to exclude study results for women whose follow-up for an abnormal mammogram was not further testing but was instead early recall for their next screening mammography. We could not exclude data for these women in 2 studies included in the review because data on women placed on early recall were combined with data on women receiving diagnostic follow-up in the study analyses (30, 31). Two investigators independently calculated a risk ratio for each study of return for the next routine mammogram. Data Synthesis and Analysis For studies assessing whether women returned for mammography, we pooled risk ratios (1 per study) by using a random-effects meta-analysis (32). For the 1 study (33) that reported data about reattendance at several time intervals after the initial mammogram, we chose data from month 18 of the study because that was the next period after the recommended screening interval of 12 months. Our analysis weighted risk ratios according to the sample size in each study while taking into account the variability among studies. We created a funnel plot to assess possible publication bias. We conducted the analyses by using the metan procedure in Stata (Stata Corp., College Station, Texas). We used 2-tailed statistical tests (critical = 0.05). Role of the Funding Sources The study was funded by grants from the University of North Carolina Lineberger Comprehensive Cancer Center and the American Cancer Society. The funding sources had no role in conducting the review or in preparing and submitti