title: Performance of anal cytology in a clinical setting when measured against histology and high-resolution anoscopy findings.
abstract: OBJECTIVE
  The success of cervical cytology in screening for cervical neoplasia has led to the concept of anal cytology screening for anal neoplasia. Our objective is to study the performance of anal cytology as a screening tool.
  
  
  METHODS
  We assessed anal cytology against histology and high-resolution anoscopy in a clinical setting.
  
  
  METHODS
  Anal pap test was obtained prior to high-resolution anoscopy examinations and biopsies. The results were analysed against a number of patient variables.
  
  
  RESULTS
  From 395 individuals (93% men), 584 anal pap tests were obtained. HIV status was positive in 212 (54%) and negative in 156 (39%) individuals. On the basis of 288 histology results, the sensitivity of anal cytology to detect disease was 70% [95% confidence interval (CI) 64-75], whereas the specificity was 67% (95% CI 38-88). For high-grade disease (anal intraepithelial neoplasia 2/3), sensitivity of anal cytology was 81% (95% CI 70-90), and the negative predictive value was 85% (95% CI 76-92). Sensitivity was dependent on the area of disease (86% for two or more quadrants vs. 69% for one or more quadrants, P = 0.002) and HIV positivity (76% in HIV positive vs. 59% in HIV negative, P = 0.009). Amongst HIV-positive patients, the sensitivity was 90% when CD4 cell count was 400 cells/microl or less compared with 67% when CD4 cell count was above 400 cells/microl (P = 0.005).
  
  
  CONCLUSIONS
  Anal cytology performs similar to cervical cytology in a clinical setting. Sensitivity of anal smear is dependent on the area (quadrants) of disease present. Sensitivity of anal cytology is enhanced when CD4 cell count is less than 400 cells/microl in HIV-positive men. Our results may explain the variable sensitivity reported in the literature.
authors.affiliation: Department of Sexual Health, Homerton University Hospital NHS Foundation Trust, London E9 6SR, UK. mayura.nathan@homerton.nhs.uk
authors.forename: Mayura
authors.initials: M
authors.lastname: Nathan
authors.forename: Naveena
authors.initials: N
authors.lastname: Singh
authors.forename: Nigel
authors.initials: N
authors.lastname: Garrett
authors.forename: Nicola
authors.initials: N
authors.lastname: Hickey
authors.forename: Teresa
authors.initials: T
authors.lastname: Prevost
authors.forename: Michael
authors.initials: M
authors.lastname: Sheaff
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000473:pathology* / Q000821:virology; D001005:Anus Neoplasms / Q000473:pathology* / Q000821:virology; D018791:CD4 Lymphocyte Count; D002278:Carcinoma in Situ / Q000473:pathology* / Q000821:virology; D005260:Female; D015658:HIV Infections / Q000473:pathology* / Q000821:virology; D006801:Humans; D008297:Male; D027383:Papillomaviridae / Q000302:isolation & purification*; D030361:Papillomavirus Infections / Q000473:pathology* / Q000821:virology; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D006113:United Kingdom / Q000453:epidemiology