Authors' objectives:

The 2007 anal dysplasia screening evidence review considered the role of the anal Pap test as a screening test for anal dysplasia in patients at high risk of anal SCC. The screening process is now thought to be improved with the addition of testing for the human papillomavirus (HPV) in high-risk populations. High-resolution anoscopy (a method to view the rectal area, using an anoscope, a lighted instrument inserted into the rectum) rather than routine anoscopy-guided biopsy, is also now considered to be the diagnostic standard. The request for the review was submitted by the Acquired Immunodeficiency Syndrome (AIDS) Bureau in the Ontario Ministry of Health and Long-Term Care, and by the director of the immunodeficiency clinic at the Toronto General Hospital.

Authors' results and conclusions: No direct evidence was found for the existence of controlled studies evaluating the effectiveness of anal Pap test screening programs for impact on anal cancer morbidity or mortality. In addition, no studies were found on the use of HPV DNA testing in the screening or diagnostic setting for anal dysplasia. The reported prevalence of HPV infection in high-risk groups, particularly HIV-positive males, however, was sufficiently high to preclude any utility of HPV testing as an adjunct to anal Pap testing. Nine reports involving studies in the United States, United Kingdom, and Canada were identified that evaluated the performance characteristics of anal Pap test screening for anal dysplasia. All involved hospital-based specialty HIV/AIDS care clinics with mainly HIV-positive males. All studies involved experienced pathologists, so the results generally represent best-case scenarios. Estimates of anal Pap test sensitivity and specificity were highly variable, and depended on the varying prevalence of cytology abnormality and differential thresholds for abnormality for both cytology and histopathology. In the largest study of HIV-positive males, sensitivity varied from 46% (95% confidence interval [CI], 36%;56%) to 69% (95% CI, 60%;78%). Specificity ranged from 59% (95% CI, 53%; 65%) to 81% (95% CI, 76%;85%). In the only study of HIV-negative males, sensitivity ranged from 26% (95% CI, 5%- 47%) to 47% (95% CI, 26%;68%). Specificity ranged from 81% (95% CI, 76%;85%) to 92% (95% CI, 89%;95%). In comparison, cervical Pap testing has also been evaluated mainly in settings where there is a high prevalence of the disease, and estimates of sensitivity and specificity were also low and highly variable. In a systematic review involving cervical Pap testing, sensitivity ranged from 30% to 87% (mean, 47%) and specificity from 86% to 100% (mean, 95%).

Authors' recommendations: No direct evidence exists to support the effectiveness of an anal Pap test screening program to reduce anal cancer mortality or morbidity. There are, however, strong parallels with cervical pap testing for cervical cancer. Sexually transmitted HPV viral infection is currently the acknowledged common causative agent for both anal and cervical cancer. Anal cancer rates in high-risk populations are approaching those of cervical cancer before the implementation of Pap testing. The anal Pap test, although it has been mainly evaluated only in HIV-positive males, has similar operating characteristics of sensitivity and specificity as the cervical Pap test. In general, the treatment options for precancer dysplasia in the cervix and the anus are similar, but treatment involving a definitive surgical resection in the anus is more limited because of the higher risk of complications. A range of ablative therapies has been applied for anal dysplasia, but evidence on treatment effectiveness, tolerability and durability, particularly in the HIV-positive patient, is limited.

Authors' methods: Review

Project Status: Completed

Year Published: 2007

URL for published report: http://www.health.gov.on.ca/english/providers/program/mas/tech/reviews/pdf/rev_ads_20070919.pdf

URL for additional information: http://www.hqontario.ca/en/mas/mas_ohtas_tech_ads_20070926.html

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: Canada

Organisation Name: Medical Advisory Secretariat

Contact Address: Medical Advisory Secretariat, 20 Dundas Street West, 10th Floor, Toronto, ON M5G 2N6 CANADA. Tel: 416-314-1092l; Fax: 416-325-2364;

Contact Name: MASinfo.moh@ontario.ca

Contact Email: MASinfo.moh@ontario.ca

Copyright: Medical Advisory Secretariat, Ontario Ministry of Health and Long-Term Care (MAS)