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Session 156 Poster Abstracts
Human Papilloma Virus Infection and Malignancies
Thursday, 1:30 - 3:30 pm
Hall B


899    
Anal Cancer Screening: Test Characteristics of Cytology and Oncogenic HPV testing for the Detection of Anal Dysplasia
Irv Salit*1, J Tinmouth2, A Lytwyn3, W Chapman4, J Mahony5, and J Raboud6
1Toronto Gen Hosp, Canada; 2Sunnybrook and Women's Hosp,Toronto, Canada; 3McMaster Univ, Hamilton, Canada; 4Univ Hlth Network,Toronto, Canada; 5McMaster Univ, Hamilton, Canada; and 6Univ of Toronto, Canada

Background:  HIV+ men remain at high risk for anal cancer despite the use of HAART. We initiated an anal cancer screening study using anal Pap smears, human papillomavirus (HPV) detection and high resolution anoscopy with directed anal biopsy. The aim of this study was to determine the test characteristics of the anal Pap smear and oncogenic HPV testing for the detection of histologic high-grade squamous intra-epithelial lesions (HSIL).

Methods:  Subjects were HIV+ men with a history of anal receptive intercourse. Cytology specimens were obtained by vigorously rotating Dacron swabs in the anal canal. Papanicolaou smears were prepared using a liquid-based method (ThinPrepä). Presence or absence of oncogenic HPV was determined using the Hybrid Capture assay. The Pap smears and biopsies were independently assessed by 4 blinded pathologists using the Bethesda criteria. Results were analyzed using these consensus diagnoses. The reference standard was the consensus diagnosis of histologic HSIL. 

Results:  Results are presented on 195 subjects (median age 45, median CD4 400, median viral load < 50, 89% on HAART). Pap smears were abnormal in 74% of subjects: HSIL in 12%, low-grade changes in 51%, and ASCUS in 11%.  Anal biopsies were abnormal in 69%: HSIL in 31% and LSIL in 38%. The sensitivity of any abnormality on the Pap for detecting histologic HSIL was 87% and the specificity was 31%. Negative predictive value was 84%, positive predictive value was 37% and the Pap smears missed detecting only 8/61 histologic HSIL lesions. HSIL on Pap smear testing was not strongly predictive of histologic HSIL. Of 23 patients with HSIL on Pap smear testing, only 12 (52%) had histologic HSIL; sensitivity was 52% and specificity was 92%. Oncogenic HPV was found in 85% of subjects. The presence of HPV had a sensitivity of 96%, specificity of 21%, negative predictive value of 93%, positive predictive value of 37%. Detection of HPV missed only 2/58 HSIL. 

Conclusions:  High rates of dysplasia have been detected during anal cancer screening. Any abnormality on the Pap smear was sensitive but not specific in detecting HSIL. Detection of oncogenic HPV had similar performance characteristics to the Pap smear.

Keywords: Malignancy; Anal Cancer; HPV