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Influence of personal characteristics of individual women on sensitivity and specificity of mammography in the Million Women Study: cohort study

BMJ 2004; 329 doi: (Published 26 August 2004) Cite this as: BMJ 2004;329:477
  1. Emily Banks, deputy director (emily.banks{at},
  2. Gillian Reeves, statistical epidemiologist1,
  3. Valerie Beral, director1,
  4. Diana Bull, senior statistician1,
  5. Barbara Crossley, chief data manager1,
  6. Moya Simmonds, clinical coordinator1,
  7. Elizabeth Hilton, clinical coordinator1,
  8. Stephen Bailey, clinical director2,
  9. Nigel Barrett, clinical director3,
  10. Peter Briers, clinical director4,
  11. Ruth English, clinical director5,
  12. Alan Jackson, consultant radiologist6,
  13. Elizabeth Kutt, clinical director7,
  14. Janet Lavelle, clinical director8,
  15. Linda Rockall, clinical director9,
  16. Matthew G Wallis, clinical director10,
  17. Mary Wilson, clinical director11,
  18. Julietta Patnick, national coordinator12
  1. 1 Cancer Research UK Epidemiology Unit, Gibson Building, Radcliffe Infirmary, Oxford OX2 6HE
  2. 2 Breast Screening Service, Princess of Wales Community Hospital, Bromsgrove B61 0BB
  3. 3 West of London Breast Screening Service, Charing Cross Hospital, London W6 8RF
  4. 4 Gloucestershire Breast Screening Service, Linton House, Cheltenham GL53 7AS
  5. 5 Breast Care Unit, Oxford Radcliffe Hospital NHS Trust, Churchill Hospital, Oxford OX3 7JH
  6. 6 Patricia Massey Breast Screening Unit, Queen Alexandra Hospital, Cosham, Portsmouth PO6 3LY
  7. 7 Avon Breast Screening, Central Health Clinic, Tower Hill, Bristol BS2 0JD
  8. 8 North Lancashire Breast Screening Service, Royal Lancaster Infirmary, Ashton Court, Lancaster LA1 4GG
  9. 9 West Sussex Breast Screening Service, Worthing Hospital, Worthing BN11 2DH
  10. 10 Breast Screening Unit, Coventry and Warwick Hospital, Coventry CV1 4FH
  11. 11 Greater Manchester Breast Screening Service, Nightingale Centre, Withington Hospital, Manchester M20 0PT
  12. 12 NHS Breast Screening Programme, Manor House, Sheffield S11 9PS
  1. Correspondence to: E Banks
  • Accepted 6 July 2004


Objectives To examine how lifestyle, hormonal, and other factors influence the sensitivity and specificity of mammography.

Methods Women recruited into the Million Women Study completed a questionnaire about various personal factors before routine mammographic screening. A sample of 122 355 women aged 50-64 years were followed for outcome of screening and incident breast cancer in the next 12 months. Sensitivity and specificity were calculated by using standard definitions, with adjustment for potential confounding factors.

Results Breast cancer was diagnosed in 726 (0.6%) women, 629 in screen positive and 97 in screen negative women; 3885 (3.2%) were screen positive but had no subsequent diagnosis of breast cancer. Overall sensitivity was 86.6% and specificity was 96.8%. Three factors had an adverse effect on both measures: use of hormone replacement therapy (sensitivity: 83.0% (95% confidence interval 77.4% to 87.6%), 84.7% (73.9% to 91.6%), and 92.1% (87.6% to 95.0%); specificity: 96.8% (96.6% to 97.0%), 97.8% (97.5% to 98.0%), and 98.1% (98.0% to 98.2%), respectively, for current, past, and never use); previous breast surgery v no previous breast surgery (sensitivity: 83.5% (75.7% to 89.1%) v 89.4% (86.5% to 91.8%); specificity: 96.2% (95.8% to 96.5%) v 97.4% (97.3% to 97.5%), respectively); and body mass index < 25 v ≥ 25 (sensitivity: 85.7% (81.2% to 89.3%) v 91.0% (87.5% to 93.6%); specificity: 97.2% (97.0% to 97.3%) v 97.4% (97.3% to 97.6%), respectively). Neither sensitivity nor specificity varied significantly according to age, family history of breast cancer, parity, past oral contraceptive use, tubal ligation, physical activity, smoking, or alcohol consumption.

Conclusions The efficiency, and possibly the effectiveness, of mammographic screening is lower in users of hormone replacement therapy, in women with previous breast surgery, and in thin women compared with other women.


  • We thank the many women who completed questionnaires for this study. We are grateful to the staff at the collaborating breast screening units and at the Million Women Study coordinating centre for their valuable contribution to the study.

  • Contributors EB, GR, VB, and JP had the original idea for the study, with important input on practical aspects of study design from DB, BC, EH, and MS. EB and DB analysed the data and EB, GR, VB, and JP interpreted the data. SB, NB, PB, RE, AJ, EK, JL, LR, MGW, and MW contributed to local study design and conduct. All the authors participated in drafting the paper and gave final approval of the version to be published. EB, GR, VB, and DB are guarantors for the study

  • Funding The Million Women Study is supported by Cancer Research UK, the Medical Research Council, and the NHS breast screening programme.

  • Competing interests None declared.

  • Ethical approval The study was approved by the Anglia and Oxford multicentre research ethics committee.

  • Accepted 6 July 2004
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