C. Gotay, C. Kawamoto, A. Bottomley, and F. Efficace, The Prognostic Significance of Patient-Reported Outcomes in Cancer Clinical Trials, Journal of Clinical Oncology, vol.26, issue.8, pp.1355-1363, 2008.
DOI : 10.1200/JCO.2007.13.3439

C. Gotay, J. Lipscomb, and C. Snyder, Reflections on Findings of the Cancer Outcomes Measurement Working Group: Moving to the Next Phase, JNCI Journal of the National Cancer Institute, vol.97, issue.21, pp.1568-1574, 2005.
DOI : 10.1093/jnci/dji337

D. Cella, J. Beaumont, K. Webster, J. Lai, and L. Elting, Measuring the concerns of cancer patients with low platelets counts: the Functional

J. Bjorner, P. Maa, M. Groenvold, N. Aaronson, M. Ahlner-elmqvist et al., Use of item response theory to develop a shortened version of the EORTC QLQ-C30 emotional functioning scale, Quality of Life Research, vol.54, issue.5, pp.1683-1697, 2004.
DOI : 10.1007/s11136-004-7866-x

S. Garcia, D. Cella, S. Clauser, K. Flynn, T. Lad et al., Standardizing Patient-Reported Outcomes Assessment in Cancer Clinical Trials: A Patient-Reported Outcomes Measurement Information System Initiative, Journal of Clinical Oncology, vol.25, issue.32, pp.5106-5112, 2007.
DOI : 10.1200/JCO.2007.12.2341

G. Fisher and I. Molenaar, Rasch Models, Foundations, Recent Developments, and Applications New, 1995.

G. Rasch, Probabilistic models for some intelligence and attainment tests Chicago, 1980.

G. Masters, A rasch model for partial credit scoring, Psychometrika, vol.47, issue.2, pp.149-174, 1982.
DOI : 10.1007/BF02296272

J. Cohen, Statistical Power Analysis for the Behavioral Sciences, 1988.

. Statacorp, Stata: Release 11. Statistical Software. College Station, TX: StataCorp LP, 2009.

J. Hardouin, Rasch analysis: estimation and tests wit the raschtest module, The Stata Journal, vol.7, pp.22-44, 2007.

C. Glas, The derivation of some tests for the rasch model from the multinomial distribution, Psychometrika, vol.1, issue.4, pp.525-546, 1988.
DOI : 10.1007/BF02294405

S. Walters and M. Campbell, The use of bootstrap methods for estimating sample size and analysing health-related quality of life outcomes, Statistics in Medicine, vol.163, issue.7, pp.1075-1102, 2005.
DOI : 10.1002/sim.1984

R. Holman, C. Glas, and R. De-haan, Power analysis in randomized clinical trials based on item response theory, Controlled Clinical Trials, vol.24, issue.4, pp.390-410, 2003.
DOI : 10.1016/S0197-2456(03)00061-8

J. Whitehead, Sample size calculations for ordered categorical data, Statistics in Medicine, vol.12, issue.24, pp.2257-2271871, 1993.
DOI : 10.1002/sim.4780122404

C. Glas, H. Geerlings, M. Laar-van-de, and E. Taal, Analysis of longitudinal randomized clinical trials using item response models, Contemporary Clinical Trials, vol.30, issue.2, pp.158-170, 2009.
DOI : 10.1016/j.cct.2008.12.003

M. Chang, Adaptive design theory and implementation using SAS and R Boca Raton: Chapman & Hall/CRC Biostatistics series, 2008.