[R] Propensity score and three treatments

[Frank E Harrell Jr]

Giovanni Parrinello wrote:
> Dear All,
> I would like to find something ( references, code,..)  to implement a
> comparison of three
> treatments in an observational study using the 'Propensity Score'.
> Any help is much appreciated. Thanks!
> Giovanni
> 
@Article{tch05use,
   author =               {Tchernis, Rusty and {Horvitz-Lennon}, Marcela and
Normand, {Sharon-Lise} T.},
   title =                {On the use of discrete choice models for 
causal infere
nce},
   journal =      Stat in Med,
   year =                 2005,
   volume =               24,
   pages =                {2197-2212},
   annote =               {causal inference;discrete choice models;matching
estimator;multi-valued treatment propensity model using discrete
choice model}
}

In one application I created 2 propensity scores and adjusted for those 
using spline functions of the logits.  See

@ARTICLE{mar94con,
   author = {Mark, D. B. and Nelson, C. L. and Califf, R. M. and 
Harrell, F. E.
            and Lee, K. L. and Jones, R. H. and Fortin, D. F. and Stack, 
R. S.
            and Glower, D. D. and Smith, L. R. and {DeLong}, E. R. and 
Smith,
            P. K. and Reves, J. G. and Jollis, J. G. and Tcheng, J. E. and
            Muhlbaier, L. H. and Lowe, J. E. and Phillips, H. R. and 
Pryor, D.
            B.},
   year = 1994,
   title = {The continuing evolution of therapy for coronary artery disease:
           {Initial} results from the era of coronary angioplasty},
   journal = {Circulation},
   volume = 89,
   pages = {2015-2025},
   annote = {CABG; PTCA; propensity; observational study; Cox model
            applications; adjusted survival curves;two propensity
   scores for three treatments}
}

I have many annotated rreferences about propensity scores in my 
bibliographic database - see the bottom of biostat.mc.vanderbilt.edu/rms
-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University