High Resolution Anoscopy (HRA) is seen as the gold diagnostic standard for the diagnosis and surveillance of AIN.
It is a reliable and well tolerated procedure that can be performed in the outpatient setting.
It’s problems lie in that the best operator outcomes are from experienced anoscopists and as the transformation rate of AIN to Anal SCC is low. In the hospital I am currently working at, which has one of the highest HIV prevalence rates in the country, 116 anoscopies needed to take place to diagnose one high risk patient with Anal SCC. (3% of anoscopies performed)
In areas with less high risk patients the yield is likely to be much lower, as such High Resolution Anoscopy has been downgraded in the American (ASCRS) guidelines to only take place if they high risk patient and an experienced anoscopists is available. In the UK, there is equipoise whether to undertake HRA, as in theory it should be beneficial but currently there is insufficient evidence to support it.
The low yield also has an effect on whether HRA is cost effective leading to some clinical centres abandoning the practice in all but the highest risk patients.
There are clinical societies such as the International Anal Intraepithelial Neoplasia Society that provide standardised HRA training and support for clinicians wishing to undertake HRA as part of their clinical practice.