title: Simultaneous marginal survival estimators when doubly censored data is present.
abstract: A doubly censoring scheme occurs when the lifetimes T being measured,from a well-known time origin, are exactly observed within a window [L, R] of observational time and are otherwise censored either from above (right-censored observations)or below (left-censored observations). Sample data consists on the pairs (U, δ)where U = min{R, max{T, L}} and δ indicates whether T is exactly observed (δ = 0),right-censored (δ = 1) or left-censored (δ = −1). We are interested in the estimation of the marginal behaviour of the three random variables T, L and R based on the observed pairs (U, δ).We propose new nonparametric simultaneous marginal estimators Ŝ(T) , Ŝ(L) and Ŝ(R) for the survival functions of T, L and R, respectively, by means of an inverse-probability-of-censoring approach. The proposed estimators Ŝ(T) , Ŝ(L) and Ŝ(R) are not computationally intensive, generalize the empirical survival estimator and reduce to the Kaplan-Meier estimator in the absence of left-censored data. Furthermore,Ŝ(T) is equivalent to a self-consistent estimator, is uniformly strongly consistent and asymptotically normal. The method is illustrated with data from a cohort of drug users recruited in a detoxification program in Badalona (Spain). For these data we estimate the survival function for the elapsed time from starting IV-drugs to AIDS diagnosis, as well as the potential follow-up time. A simulation study is discussed to assess the performance of the three survival estimators for moderate sample sizes and different censoring levels.
authors.affiliation: Departament de Probabilitat, Lògica i Estadística, Universitat de Barcelona, Gran Via 585, 08007, Barcelona, Spain. olgajulia@ub.edu
authors.forename: Olga
authors.initials: O
authors.lastname: Julià
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Gómez
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy; D019380:Anti-HIV Agents / Q000627:therapeutic use; D015331:Cohort Studies; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D006678:HIV / Q000187:drug effects / Q000254:growth & development; D006801:Humans; D053208:Kaplan-Meier Estimate; D013030:Spain; D019966:Substance-Related Disorders
chemical_list: D019380:Anti-HIV Agents