Kawaguchi et al. (2011) provided methodology and applications for a stratified Mann-Whitney estimator that addresses the same comparison between two randomized groups for a strictly ordinal response variable as the van Elteren test statistic for randomized clinical trials with strata. The sanon package provides the implementation of the method within the R programming environment (R Core Team, 2012). The usage of sanon is illustrated with five examples. The first example is a randomized clinical trial with eight strata and a univariate ordinal response variable. The second example is a randomized clinical trial with four strata, two covariables, and four ordinal response variables. The third example is a cross over design randomized clinical trial with two strata, one covariable, and two ordinal response variables. The fourth example is a randomized clinical trial with seven strata (which are managed as a categorical covariable), three ordinal covariables with missing values, and three ordinal response variables with missing values. The fifth example is a randomized clinical trial with six strata, a categorical covariable with three levels, and three ordinal response variables with missing values.
Kawaguchi, Atsushi and Koch, Gary G., "sanon : An R Package for Stratified Analysis with Nonparametric Covariable Adjustment" (January 2014). The University of North Carolina at Chapel Hill Department of Biostatistics Technical Report Series. Working Paper 41.