Blind Sampling Is Superior to Anoscope Guided Sampling for Screening for Anal Intraepithelial Neoplasia

The authors compared anal cytology smears, either those collected "blind" (swab inserted 4 cm into anal canal and rotated) or guided through an anoscope (transformation zone visualized and then sampled) in terms of patient acceptability and sample quality.

"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," the report stated. "Both techniques utilized 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."

The investigators found that "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)."

"Blind cytology smears are superior to anoscope-guided smears for screening for anal neoplasia in homosexual men," the researchers concluded.

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