title: Estimation of the standardized risk difference and ratio in a competing risks framework: application to injection drug use and progression to AIDS after initiation of antiretroviral therapy.
abstract: There are few published examples of absolute risk estimated from epidemiologic data subject to censoring and competing risks with adjustment for multiple confounders. We present an example estimating the effect of injection drug use on 6-year risk of acquired immunodeficiency syndrome (AIDS) after initiation of combination antiretroviral therapy between 1998 and 2012 in an 8-site US cohort study with death before AIDS as a competing risk. We estimate the risk standardized to the total study sample by combining inverse probability weights with the cumulative incidence function; estimates of precision are obtained by bootstrap. In 7,182 patients (83% male, 33% African American, median age of 38 years), we observed 6-year standardized AIDS risks of 16.75% among 1,143 injection drug users and 12.08% among 6,039 nonusers, yielding a standardized risk difference of 4.68 (95% confidence interval: 1.27, 8.08) and a standardized risk ratio of 1.39 (95% confidence interval: 1.12, 1.72). Results may be sensitive to the assumptions of exposure-version irrelevance, no measurement bias, and no unmeasured confounding. These limitations suggest that results be replicated with refined measurements of injection drug use. Nevertheless, estimating the standardized risk difference and ratio is straightforward, and injection drug use appears to increase the risk of AIDS.
authors: Stephen R
authors: SR
authors: Cole
authors: Bryan
authors: B
authors: Lau
authors: Joseph J
authors: JJ
authors: Eron
authors: M Alan
authors: MA
authors: Brookhart
authors: Mari M
authors: MM
authors: Kitahata
authors: Jeffrey N
authors: JN
authors: Martin
authors: William C
authors: WC
authors: Mathews
authors: Michael J
authors: MJ
authors: Mugavero
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000175:diagnosis / Q000188:drug therapy* / Q000401:mortality*; D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D008432:Mathematical Computing; D008875:Middle Aged; D016017:Odds Ratio; D018570:Risk Assessment; D012307:Risk Factors; D015819:Substance Abuse, Intravenous / Q000150:complications* / Q000208:ethnology / Q000401:mortality*; D015996:Survival Rate; D014481:United States / Q000453:epidemiology
chemical_list: D019380:Anti-HIV Agents
keywords: AIDS; HIV; cohort study; competing risks; survival function