Purpose: To investigate the prevalence of anal squamous intraepithelial lesions (ASIL) or anal cancer in patients attended at the Tropical Medicine Foundation of Amazonas.
Methods: 344 patients consecutively attended at the institution, in 2007/2008, were distributed in the following strata according to presence/abscense of at risk conditions for anal cancer: Group 1 - HIV-positive men-who-have-sex-with-men (101); Group 2 - HIV-positive females (49); Group 3 - patients without any at risk condition for anal cancer (53); Group 4 - HIV-positive heterosexual men (38); Group 5 - HIV-negative patients, without anoreceptive sexual habits, but with other at risk conditions for anal cancer (45); Group 6 - HIV-negative men-who-have-sex-with-men (26); and Group 7 - HIV-negative anoreceptive females (32). The histopathological results of biopsies guided by high-resolution anoscopy were analyzed by frequentist and bayesian statistics in order to calculate the point-prevalence of ASIL/cancer and observe any eventual preponderance of one group over the other.
Results: The point-prevalence of ASIL for all the patients studied was 93/344 (27%), the difference between HIV-positive and negative patients being statistically significant (38.3% versus 13.5%; p < 0.0001). The prevalence of ASIL for each one of the groups studied was: Group 1 = 49.5%, Group 2 = 28.6%, Group 3 = 3.8%, Group 4 = 21.1%, Group 5 = 11.1%, Group 6 = 30.8% and Group 7 = 18.8%. Standard residual analysis demonstrated that ASIL was significantly prevalent in patients of Group 1 and high-grade ASIL in patients of Group 2. The odds for ASIL of Group 1 was significantly higher in comparison to Groups 2, 3, 4, 5 and 7 (p < 0.03). The odds for ASIL of Groups 2, 4 and 6 were significantly higher in comparison to Group 3 (p < 0.03).
Conclusions: In the patients studied, ASIL (low and/or high-grade) tended to be significantly more prevalent in HIV-positive patients. Nonetheless, HIV-negative anoreceptive patients also presented great probability to have anal cancer precursor lesions, mainly those of the male gender.