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There is a strong correlation between HPV infection and anal squamous cell cancer (SCC). Just like in nearly 100% of cervical cancer, infection with human papillomavirus (HPV) high-risk types causes more than 80% of anal cancer. Nevertheless the natural history of anal cancer is not fully understood. It mostly arises from high-grade squamous intraepithelial lesion (HSIL) resp. anal intraepithelial neoplasia (AIN) . In human immunodeficiency virus (HIV)-positive men having sex with men (MSM), the prevalence of anal HPV infection is especially high (45–95%). These patients have an increased risk of anal intraepithelial neoplasia (AIN), the putative precursor of anal SCC29. The prevalence of anal SCC is increasing steadily, reaching 35 per 100 000 in HIV-negative and 135 to 225 per 100 000 in HIV-positive MSM respectively. Today, anal SCC in HIV-positive MSM is over nine times more common than cervical cancer in women and has become the most common non-AIDS defining malignancy in HIV-positive patients10,11. In view of the increasing health burden of anal cancer in HIV positive MSM and its similarities to cervical cancer, an anal cancer screening programme is recommended for this Population.

The identification of early-stage cancer, when treatment is most effective, is the basis for all surveillance recommendations. The standard for AIN screening is high resolution anoscopy (HRA) with a colposcope routinely used by gynaecologists in combination with staining with acetic acid/lugol iodine, biopsies and histopathological workup of suspicious lesions. The use of the colposcope in AIN detection has a historical tradition since premalignant cervical lesions have many similarities to AIN.
Currently, only a limited number of physicians are experienced in HRA diagnostics. First guidelines on this topic where published in October 201625.


To date there is no study comparing the traditionally used screening colposcopy technique (HRA) with the flexible endoscopy (HRE) in terms of anal AIN detection. If we could show, that endoscopy is as effective in AIN diagnosis as standard HRA, the availability of this screening examination could be increased since the flexible endoscopes are a widely available tool to gastroenterologists and surgeons (unlike a colposcope). Furthermore AIN screening could be technically improved, simplified and made more comfortable for patients. Ideally this leads to a better quality of the examination, to a higher acceptance by the patients and thereby to a reduction of the anal carcinomas in the most affected population