title: Risk of breast cancer after false-positive test results in screening mammography.
abstract: BACKGROUND
  Screening for disease in healthy people inevitably leads to some false-positive tests in disease-free individuals. Normally, women with false-positive screening tests for breast cancer are referred back to routine screening. However, the long-term outcome for women with false-positive tests is unknown.
  
  
  METHODS
  We used data from a long-standing population-based screening mammography program in Copenhagen, Denmark, to determine the long-term risk of breast cancer in women with false-positive tests. The age-adjusted relative risk (RR) of breast cancer for women with a false-positive test compared with women with only negative tests was estimated with Poisson regression, adjusted for age, and stratified by screening round and technology period. All statistical tests were two-sided.
  
  
  RESULTS
  A total of 58 003 women, aged 50-69 years, were included in the analysis. Women with negative tests had an absolute cancer rate of 339/100 000 person-years at risk, whereas women with a false-positive test had an absolute rate of 583/100 000 person-years at risk. The adjusted relative risk of breast cancer after a false-positive test was 1.67 (95% confidence interval [CI] 1.45 to 1.88). The relative risk remained statistically significantly increased 6 or more years after the false-positive test, with point estimates varying between 1.58 and 2.30. When stratified by assessment technology phase and using equal follow-up time, the false-positive group from the mid 1990s had a statistically significantly higher risk of breast cancer (RR = 1.65, 95% CI = 1.22 to 2.24) than the group with negative tests, whereas the false-positive group from the early 2000s was not statistically significantly different from the group testing negative.
  
  
  CONCLUSIONS
  The implementation of new assessment technology coincided with a decrease in the size of excess risk of breast cancer for women with false-positive screening results. However, it may be beneficial to actively encourage women with false-positive tests to continue to attend regular screening.
authors.affiliation: Department of Public Health, University of Copenhagen, Copenhagen K, Denmark. myeu@sund.ku.dk
authors.forename: My
authors.initials: M
authors.lastname: von Euler-Chelpin
authors.forename: Louise Madeleine
authors.initials: LM
authors.lastname: Risør
authors.forename: Brian Larsen
authors.initials: BL
authors.lastname: Thorsted
authors.forename: Ilse
authors.initials: I
authors.lastname: Vejborg
mesh_terms: D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D003718:Denmark / Q000453:epidemiology; D055088:Early Detection of Cancer; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography; D008875:Middle Aged; D013997:Time Factors