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Fabián Tibaldi

Publications and source records attributed to Fabián Tibaldi.

5 recordsLinked to original sources
PubMed2004

Modelling associations between time-to-event responses in pilot cancer clinical trials using a Plackett-Dale model.

This work was motivated by the need to find surrogate endpoints for survival of patients in oncology studies. The goal of this article is to determine associations between five time-to-event outcomes coming from three clinical trials for non-small cell lung cancer. To this end, we propose to use the multivariate Dale model for time-to-event data introduced by Tibaldi et al. (Stat. Med. 2003). We fit the model to these data, using a pseudo-likelihood approach to estimate the model parameters. We evaluate and compare the performance of different dimensional models and we relate the Dale model association parameter, i.e. the odds ratio, to well-known quantities such as Kendall's tau and Spearman's rho. Finally, the results are discussed with a perspective on surrogate marker validation. Some suggestions are made regarding further studies in this field.

Adjuvants, Immunologic↗
PubMed2004

Pseudo-likelihood estimation for a marginal multivariate survival model.

In this paper, we propose a multivariate Plackett-Dale model for survival outcomes. A pseudo-likelihood method for the estimation of the parameters is proposed and these ideas are applied to two case studies. The modelling approach is similar in spirit but different from Parner's approach. The first study is in AIDS, where the overall survival time and different opportunistic infections in HIV-infected patients are studied. The second study is on adoption data where the association of the survival times within families is modelled, illustrating the use of the proposed methodology for the context of population genetics.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Prentice's approach and the meta-analytic paradigm: a reflection on the role of statistics in the evaluation of surrogate endpoints.

We put a perspective on the strengths and limitations of statistical methods for the evaluation of surrogate endpoints. Whereas using several trials overcomes some of the limitations of a single-trial framework (Prentice, 1989, Statistics in Medicine 8, 431-440), arguably the evaluation of surrogate endpoints can never be done using only statistical evidence but such evidence should be seen as but one component in a decision-making process that involves, among others, a number of clinical and biological considerations. We briefly present a hierarchical framework that incorporates ideas from Prentice's work and is uniformly applicable to different types of surrogate and true clinical outcomes.

Biometry↗
PubMed2002

Psychomotor development in Argentinean children aged 0-5 years.

In Argentina, there is no information on ages of attainment of developmental milestones and very few data about environmental factors that influence them. A national survey on the psychomotor development of children under 6 years of age was carried out with the help of 129 paediatricians. Logistic regression was applied to a final sample of 3573 healthy, normal children in order to estimate selected centiles (25th, 50th, 75th and 90th), together with their respective confidence intervals, of the ages of attainment of 78 developmental items belonging to the following areas: personal-social (18 items), fine motor (19), language (18) and gross motor (23). The 50th centile obtained for each of the 43 comparable items was compared with those obtained in previously standardised tests: DDST, Denver II, Bayley and Chilean scales. Neither significant nor systematic differences were found between our results and those described in the tests used for comparison. Multiple logistic regressions showed that social class, maternal education and sex (female) were associated with earlier attainment of some selected developmental items, achieved at ages later than 1 year. Selected items achieved before the first year of life were not affected by any of the independent environmental variables studied. The information is useful in helping paediatricians in their daily practice for surveillance of development, as baseline information for epidemiological studies on development in our country and for cross-cultural analysis.

Adult↗