Accuracy of Anal Cytology for Diagnostic of Precursor Lesions of Anal Cancer: Systematic Review and Meta-analysis

BACKGROUND: Anal canal carcinoma is relevant because it commonly occurs in high-risk groups, and its incidence has been increasing. OBJECTIVE: This study evaluated the accuracy of anal cytology in the screening of precursor lesions of anal cancer, compared with histopathologic examination as the reference, in all subjects and in men who have sex with men, HIV-infected men and women, and men who have sex with men and HIV-infected subgroups. DATA SOURCES: The data included studies identified in the MEDLINE, Latin American and Caribbean Health Sciences, Cochrane Library, and Embase electronic databases, as well as in the grey literature. The search terms included anal cancer, anal dysplasia, anal intraepithelial neoplasia, screening, and anal cytology. STUDY SELECTION: After excluding studies with no histopathological data and those with duplicate and missing data, 34 primary studies were included. INTERVENTION: Cytology of anal smears was studied. MAIN OUTCOME MEASURES: Sensitivity, specificity, diagnostic OR, and area under the curve were measured. RESULTS: A total of 5093 patients were included. The pooled sensitivity of anal cytology was 85.0% (95% CI, 82.0%-87.0%) and pooled specificity was 43.2% (95% CI, 41.4%-45.1%) for the detection of anal intraepithelial neoplasia grade 2 or worse versus anal intraepithelial neoplasia grade 1 and normal when measuring all subjects. The accuracy of anal cytology was higher in the men who have sex with men and HIV-infected and men who have sex with men only subgroups. LIMITATIONS: This study was limited by its specificity. CONCLUSIONS: The study results support the hypothesis that cytology is a good test for the screening of anal cancer.