Value of high-resolution anoscopy in the diagnosis of anal precancerous lesions

Abstract

Objective: To evaluate the value of high-resolution anoscopy (HRA) in the diagnosis of anal precancerous lesions. Methods: A retrospective cohort study was performed, which included 142 patients who underwent HRA in vulvar and anal clinic at Obstetrics and Gynecology Hospital of Fudan University from January 2014 to December 2019. With the perianal and anal canal biopsy pathology as the "gold standard", the diagnostic value of HRA and specific findings for anal precancerous lesions were evaluated and the clinical characteristics of patients with anal precancerous lesions were analyzed. Results: (1) Agreement between HRA and anal pathology were 76.6% (95/124, perianal) and 70.0% (84/120, anal canal), in which there was no significant difference (χ2=1.365, P=0.243). The strength of agreement with weighted Kappa statistic were 0.604 (perianal) and 0.455 (anal canal) respectively. HRA diagnosis were more overestimated [16.9% (21/124) in perianal and 25.0% (30/120) in anal canal] than underestimated [6.5% (8/124) in perianal and 5.0% (6/120) in anal canal]. The sensitivity and specificity of HRA in the diagnosis of anal precancerous lesions were all more than 60.0% (perianal lesions: 97.8% and 74.7%; anal canal lesions: 90.9% and 66.7%), and Youden's index were >0.5 (perianal lesions: 0.725; anal canal lesions: 0.576). The positive predictive value of HRA in anal canal lesions (50.8%) was lower than that in perianal lesions (68.8%). (2) The thin acetowhite epithelium was the most common finding in anal precancerous lesions, and its performance in anal canal lesions (the sensitivity, the specificity and the Youden's index were 78.8%, 62.4% and 0.412, respectively) were better than those in perianal lesions (the sensitivity, the specificity and the Youden's index were 28.9%, 96.9% and 0.258, respectively). The dense acetowhite epithelium and vascular patterns were only seen in anal canal lesions. Lugol's iodine was little useful for perianal lesions (the incidence of iodine negative was 0),but quite useful to evaluate the canal lesions (the positive predictive value was 83.3% and the negative predictive value was 82.3%). (3) The average age of patients with low-grade anal precancerous lesion was (37±10) years old, and high-grade anal precancerous lesion was (42±11) years old, and there was significant difference between them (P=0.034). Age curve showed that the peak age was 30-40 years old. Vulvar intraepithelial lesion was the risk factor of anal precancerous lesions (χ2=4.284, P<0.05). Conclusions: HRA patterns are reliable in the diagnosis of anal precancerous lesions, which is important for guiding biopsy. However, it is easy to be overestimated, especially for anal canal lesions. The acetowhite epithelium is the most common finding in anal precancerous lesions, but vascular patterns are only seen in anal canal lesions.