29. WHAT DO ANAL CYTOLOGY RESULTS MEAN?

Abstract

Background: Between 1970 and 2000 in Australia, anal cancer rates have increased over fourfold. Furthermore, the prevalence rate of anal cancer in MSM is approximately 35 cases/100 000, comparable to that of cervical cancer in women prior to the introduction of the national cervical screening program. These observations have led to calls for the introduction of targeted anal cytological screening program for MSMs. Our study examined the effectiveness of anal cytological testing in detecting histologically proven high grade anal intraepithelial neoplasia (HGAIN, also known as AIN2 & 3).

Methods: A retrospective case note review of people attending an anal dysplasia clinic from July 2002 to May 2007 was performed. Cytological results of anal swabs were compared to results of biopsies obtained through high resolution anoscopy.

Results: 436 anal cytological results were identified. Of these, 5% were unsatisfactory, 51% showed low grade changes and 44% showed high grade changes. 185 cases were then paired with corresponding histological results.

Analysing the data from the perspective of diagnosing histologically proven HGAIN, anal swab cytological abnormalities revealed a sensitivity of 54% and specificity of 90% for the most recent cytological test and 83% and 39% respectively, when analysed according to most serious cytological result ever.

Conclusions: Our sensitivities of 54-83% and specificities of 39-90% are consistent with those found with cervical cytology, but emphasize the need for caution in their interpretation. However, before any anal cytological screening programs are introduced, it is important to also establish that treatment of any high grade anal dysplasia detected by such screening is of value in preventing progression to cancer.