title: Optimal caliper width for propensity score matching of three treatment groups: a Monte Carlo study.
abstract: Propensity score matching is a method to reduce bias in non-randomized and observational studies. Propensity score matching is mainly applied to two treatment groups rather than multiple treatment groups, because some key issues affecting its application to multiple treatment groups remain unsolved, such as the matching distance, the assessment of balance in baseline variables, and the choice of optimal caliper width. The primary objective of this study was to compare propensity score matching methods using different calipers and to choose the optimal caliper width for use with three treatment groups. The authors used caliper widths from 0.1 to 0.8 of the pooled standard deviation of the logit of the propensity score, in increments of 0.1. The balance in baseline variables was assessed by standardized difference. The matching ratio, relative bias, and mean squared error (MSE) of the estimate between groups in different propensity score-matched samples were also reported. The results of Monte Carlo simulations indicate that matching using a caliper width of 0.2 of the pooled standard deviation of the logit of the propensity score affords superior performance in the estimation of treatment effects. This study provides practical solutions for the application of propensity score matching of three treatment groups.
authors.affiliation: Medical Department, The 309th Hospital of Chinese People's Liberation Army, Beijing, China ; Department of Health Statistics, The Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Yongji
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Information Center, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Cai
authors.affiliation: Department of Health Statistics, The Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Chanjuan
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Health Statistics, The Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Jiang
authors.affiliation: Department of Health Statistics, The Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Gastroenterology, The 309th Hospital of Chinese People's Liberation Army, Beijing, China.
authors.forename: Jiugang
authors.initials: J
authors.lastname: Song
authors.affiliation: Department of Health Statistics, The Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Jielai
authors.initials: J
authors.lastname: Xia
mesh_terms: D006801:Humans; D015233:Models, Statistical; D008962:Models, Theoretical; D009010:Monte Carlo Method; D057216:Propensity Score