Effect of False-Positive Mammograms on Interval Breast Cancer Screening in a Health Maintenance Organization

Background: Despite the mortality benefits of breast cancer screening, not all women receive regular mammography. Such factors as age, socioeconomic status, and physician recommendation have been associated with greater use of screening. However, we do not know whether having an abnormal mammogram affects future screening. Objective: To examine the effect of a false-positive mammogram on adherence to the next recommended screening mammogram. Design: Prospective cohort study. Setting: The breast cancer screening program at Group Health Cooperative, a health maintenance organization in Washington state. Patients: 5059 women 40 years of age or older with no history of breast cancer or breast surgery who had false-positive (n = 813) or true-negative (n = 4246) index screening mammograms between 1 August 1990 and 31 July 1992. Measurements: Screening rates and odds ratios for recommended interval screening up to 42 months after the index mammogram. Results: After adjustment for differences in age; previous use of mammography; family history of breast cancer; exogenous hormone use; and age at menarche, first child-birth, and menopause, women with false-positive index mammograms were more likely than those with true-negative index mammograms to obtain their next recommended screening mammogram (odds ratio, 1.21 [95% CI, 1.01 to 1.45]). The relation between a false-positive mammogram and the likelihood of adherence to screening in the next recommended interval was strongest among women who had not previously undergone mammography (odds ratio, 1.66 [CI, 1.26 to 2.17]). Conclusions: Having a false-positive mammogram did not adversely affect screening behavior in the next recommended interval. Women with false-positive mammograms, especially those without previous mammography, were more likely to return for the next scheduled screening. Ann Intern Med. 1999;131:1-6.
Women who have had a false-positive mammogram did not become alienated from regular screening, but in fact were more likely to return for the next scheduled screening than others. Of 5,059 women over 40 years of age with no history of breast cancer or breast surgery, 813 had false-positive results. Following up intermittently for up to 42 months, and after adjusting for differences in age, previous mammograms, family histories, and such, the women who had false-positives were more likely to return for the next screening by a ratio of 1.21 to 1.00. Those for whom this was the first mammogram returned at a rate of 1.66 to 1.00