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Blind sampling is superior to anoscope guided sampling for screening for anal intraepithelial neoplasia
  1. C M Vajdic1,
  2. J S Anderson1,2,
  3. R J Hillman3,
  4. G Medley4,
  5. A E Grulich1
  1. 1National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, Australia
  2. 2Carlton Clinic, Melbourne, Australia
  3. 3Sexually Transmitted Infections Research Centre, Westmead Hospital, Sydney, Australia, and, Albion Street Clinic, Sydney, Australia
  4. 4Dorevitch Pathology, Mayne Health, Melbourne, Australia
  1. Correspondence to:
 Claire Vajdic
 National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Level 2/376 Victoria Street, Sydney, NSW, 2010, Australia;


Objectives: Anal cytology smears are either collected “blind” (swab inserted 4 cm into anal canal and rotated) or guided through an anoscope (transformation zone visualised and then sampled). We compared these smear techniques with respect to sample quality and patient acceptability.

Methods: Using a paired, random sequence clinical trial, 151 homosexual men (n = 95 HIV positive) underwent both smear techniques at a single visit; smear order was randomised and specimens were read blind. Both techniques utilised a Dacron swab, with water lubrication. Cytological specimens were prepared using a liquid based collection method (ThinPrep). The outcome measures were cytological specimen adequacy, cytological classification, presence of rectal columnar, squamous and metaplastic cells, contamination, patient comfort and acceptability, and volume of fluid that remained after the ThinPrep procedure.

Results: Regardless of smear order, guided smears were less likely to detect higher grade abnormalities than blind smears (15 v 27 cases, p = 0.001). Controlling for smear order, guided smears were more likely to be assessed as “unsatisfactory” for cytological assessment (OR 6.93, 95% CI 1.92 to 24.94), and contain fewer squamous (OR 0.20, 95% CI 0.04 to 0.94) and metaplastic cells (OR 0.12, 95% CI 0.03 to 0.54) than blind smears; there were no other statistically significant differences between techniques. Regardless of smear technique, first performed smears were more likely to detect a higher grade abnormality than second performed smears (23 v eight cases, p<0.001).

Conclusions: Blind cytology smears are superior to anoscope guided smears for screening for anal neoplasia in homosexual men.

  • AIN, anal intraepithelial neoplasia
  • ASCUS, atypical squamous cells of undetermined significance
  • HPV, human papillomavirus
  • HGSIL, high grade squamous intraepithelial lesion
  • LGSIL, low grade squamous intraepithelial lesion
  • MSM, men who have sex with men
  • anal neoplasia
  • homosexual men
  • screening

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  • Support: Cytyc Corporation Australia provided ThinPrep vials containing PreservCyt transport medium and ThinPrep Filters.

  • Competing interests: The authors have no possible conflicts of interest, including financial, consultant, institutional, or other relationships that might lead to bias or conflict of interest.