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Anal cancer incidence rates by calendar era for human immunodeficiency virus infected men who have sex with men (MSM), other men, and women, North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD), years 1996–2007. Vertical lines are 95% confidence intervals. P values from the Poisson regression model compare rates by calendar era with 2000–2003 as reference. The global P value for comparison of rates across eras is based on the likelihood ratio statistic.
