title: Evaluating cytology for the detection of invasive cervical cancer.
abstract: OBJECTIVE
  To assess the sensitivity, the number needed to screen (NNS) and the positive predictive value (PPV) of cervical cytology for the diagnosis of cancer by age in a screening population.
  
  
  METHODS
  A retrospective cohort of women with invasive cervical cancer nested within a census of cervical cytology. All (c. 8 million) women aged 20-64 years with cervical cytology (excluding tests after an earlier abnormality). From April 2007 to March 2010, 3372 women had cervical cancer diagnosed within 12 months of such cytology in England. The sensitivity of cervical cytology to cancer, NNS to detect one cancer and predictive values of cytology were calculated for various 'referral' thresholds. These were calculated for ages 20-24, 25-34, 35-49 and 50-64 years.
  
  
  RESULTS
  The sensitivity of at least moderate dyskaryosis [equivalent to a high-grade squamous intraepithelial lesion (HSIL) or worse] for cancer of 89.4% [95% confidence interval (CI) 88.3-90.4%] in women offered screening was independent of age. At all ages, women with borderline-early recall or mild dyskaryosis on cytology (equivalent to ASC-US and LSIL, respectively, in the Bethesda system) had a similar risk of cervical cancer to the risk in all women tested. The PPV of severe dyskaryosis/?invasive and ?glandular neoplasia cytology (equivalent to squamous cell carcinoma and adenocarcinoma/adenocarcinoma in situ, respectively, in the Bethesda System) were 34% and 12%, respectively; the PPV of severe dyskaryosis (HSIL: severe dysplasia) was 4%. The NNS was lowest when the incidence of cervical cancer was highest, at ages 25-39 years, but the proportion of those with abnormal cytology who have cancer was also lowest in younger women.
  
  
  CONCLUSIONS
  The PPV of at least severe dyskaryosis (HSIL: severe dysplasia) for cancer was 4-10% of women aged 25-64 years, justifying a 2-week referral to colposcopy and demonstrating the importance of failsafe monitoring for such patients. The sensitivity of cytology for cervical cancer was excellent across all age groups.
authors.affiliation: Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Bart's & The London School of Medicine, Queen Mary University of London, London, UK.
authors.forename: R
authors.initials: R
authors.lastname: Landy
authors.affiliation: Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Bart's & The London School of Medicine, Queen Mary University of London, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Castanon
authors.affiliation: College House, St Luke's Campus, Exeter, UK.
authors.forename: W
authors.initials: W
authors.lastname: Hamilton
authors.affiliation: Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Bart's & The London School of Medicine, Queen Mary University of London, London, UK.
authors.forename: A W W
authors.initials: AW
authors.lastname: Lim
authors.affiliation: Cytology Department, Sheffield Teaching Hospitals, NHS Foundation Trust, Sheffield, UK.
authors.forename: N
authors.initials: N
authors.lastname: Dudding
authors.affiliation: Whipps Cross University, Hospital, Barts Health NHS Trust, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Hollingworth
authors.affiliation: Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Bart's & The London School of Medicine, Queen Mary University of London, London, UK.
authors.forename: P D
authors.initials: PD
authors.lastname: Sasieni
mesh_terms: D000328:Adult; D065309:Atypical Squamous Cells of the Cervix / Q000473:pathology*; D002584:Cervix Uteri / Q000473:pathology*; D003127:Colposcopy; D003581:Cytodiagnosis / Q000379:methods*; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D008875:Middle Aged; D065006:Papanicolaou Test; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D065310:Squamous Intraepithelial Lesions of the Cervix / Q000175:diagnosis* / Q000473:pathology; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis* / Q000473:pathology; D014626:Vaginal Smears; D055815:Young Adult; D002578:Uterine Cervical Dysplasia / Q000175:diagnosis* / Q000473:pathology
keywords: cervical cancer; cervical cytology; pap test; predictive value of tests; sensitivity; specificity