Histological outcomes of anal high-grade cytopredictions.

BACKGROUND: Longitudinal studies of histological outcomes after anal cytological screening in men who have sex with men (MSM) are rare. This study measured the positive predictive values (PPVs) of each level of baseline cytological abnormality in MSM in Sydney, Australia, over a 12-month period. METHODS: The Study of the Prevention of Anal Cancer is a 3-year prospective study of the natural history of anal human papillomavirus infection in MSM at least 35 years old. For each participant with a baseline cytological abnormality, the worst histology was recorded at the baseline high-resolution anoscopy and at 6 and 12 months. PPVs for a histological high-grade squamous intraepithelial lesion (HSIL) diagnosis were calculated for each level of baseline cytological abnormality at each time point. RESULTS: Among 424 men who completed 3 visits, the PPV of a cytological HSIL increased from 71.6% at the baseline to 86.4% at 6 months and to 92.6% at 12 months (P < .001). For cytological atypical squamous cells, cannot rule out high-grade squamous intraepithelial lesion (ASC-H), the PPV increased from 51.5% at the baseline to 69.7% at 6 months and to 75.8% at 12 months (P = .004). At each time point, the PPV of a cytological HSIL was significantly higher than the PPV of ASC-H. The PPV of low-grade cytology reports was significantly lower than the PPV of ASC-H at each time point. CONCLUSIONS: In a cohort of MSM, a baseline histological HSIL diagnosis after an HSIL cytoprediction is high, and it increases with further examinations over the course of 12 months. Lower levels of cytological abnormalities have significantly lower PPVs. These data can inform patient management and the quality assessment of each aspect of the screening pathway. Cancer Cytopathol 2018;126:136-44. © 2017 American Cancer Society.

Comparison of the performance of anal cytology and cervical cytology as screening tests.

Cervical cytology screening has a long history and has successfully reduced the impact of cervical cancer in many countries. Anal cytology is a relative newcomer and anal screening is currently offered in only a few centres around the world. Many questions need to be answered before anal screening is more widely adopted. While there are many similarities between cervical and anal squamous cell carcinoma, there are also important differences: differences in the prevalence of disease, in the 'at-risk' target populations and possibly in the robustness of the reference standard of biopsy. The performance of cytology as a screening test in the literature varies widely but it is essential to understand that some of this variability is due to differences in the definitions of key parameters in the various studies. For cervical screening, estimates of sensitivity have ranged from 19% to 94% and specificity from 94% to 98%. For anal screening, data are fewer and more limited. Estimates of the sensitivity of anal cytology in men who have sex with men and HIV-positive populations have ranged from 55% to 87% and specificity from 37% to 76%. Ultimately, rather than comparing anal with cervical cytology, it may be more helpful to assess the value of anal cytology independently through well designed trials.