title: Effect of start age of breast cancer screening mammography on the risk of false-positive results.
abstract: OBJECTIVE
  To estimate the false-positive (FP) risk according to the start age of mammography screening (45-46 or 50-51 years).
  
  
  METHODS
  Data from eight regions of the Spanish breast cancer screening programme from 1990 to 2006 were included (1,565,364 women). Discrete time-hazard models were used to ascertain the effect of age and time-related, programme-related and personal variables on FP leading to any further procedure and to invasive procedures (FPI). In a subset we estimated the differential FP risk of starting screening at 45-46 years (175,656 women) or 50-51 (251,275).
  
  
  RESULTS
  A start age of 45-46 versus 50-51 years increased both FP (OR=1.20; 95%CI: 1.13-1.26) and FPI risks (OR=1.43 (95%CI: 1.18-1.73).Other factors increasing FP risk were premenopausal status (FP OR=1.26; 95%CI: 1.23-1.29 and FPI OR=1.22; 95%CI: 1.13-1.31), prior invasive procedures (FP OR=1.52; 95%CI: 1.47-1.57 and FPI (OR=2.08; 95%CI: 1.89-2.28) and family history (FP OR=1.16; 95%CI: 1.12-1.20 and FPI OR=1.26; 95%CI: 1.13-1.41). FP risk was increased by double reading (OR=1.36; 95%CI: 1.23-1.51) and FPI risk by double views (OR=1.34; 95%CI: 1.18-1.52). Both the cumulative FP and FPI risks were higher in women commencing screening at 45-46 years versus 50-51 years (33.30% versus 20.39% and 2.68% versus 1.76%).
  
  
  CONCLUSIONS
  Starting screening earlier increases the cumulative risk of FP and FPI.
authors.affiliation: General Directorate Public Health and Centre for Public Health Research (CSISP), Avda. Catalunya 21, Valencia, Spain. salas_dol@gva.es
authors.forename: Dolores
authors.initials: D
authors.lastname: Salas
authors.forename: Josefa
authors.initials: J
authors.lastname: Ibáñez
authors.forename: Rubén
authors.initials: R
authors.lastname: Román
authors.forename: Dolores
authors.initials: D
authors.lastname: Cuevas
authors.forename: Maria
authors.initials: M
authors.lastname: Sala
authors.forename: Nieves
authors.initials: N
authors.lastname: Ascunce
authors.forename: Raquel
authors.initials: R
authors.lastname: Zubizarreta
authors.forename: Xavier
authors.initials: X
authors.lastname: Castells
mesh_terms: D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008327:Mammography / Q000592:standards* / Q000706:statistics & numerical data*; D008875:Middle Aged; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012307:Risk Factors; D013030:Spain