Plenary Lecture
Parametric and Nonparametric Approaches to Evaluate the Agreement of Medical Measurements
Professor Luís M. Grilo
Instituto Politécnico de Tomar
Unidade Departamental de Matemática e Física and Centro de Matemática e Aplicações
(CMA), FCT/UNL
Portugal
Email: lgrilo@ipt.pt
Abstract: The well-known limits of agreement are usually used to evaluate the agreement between two alternative medical measurements methods, when the distribution of their differences is normal. In this case study the empirical distribution of the differences of serum levels of vitamin B12 in a blood sample does not verify the assumption of this parametric approach, since it is positive skewed, leptokurtic and has some outliers. Thus, the limits of agreement are also estimated after a Box Cox transformation, for an appropriate regression and for a nonparametric approach. A bootstrap resampling method is also used in order to obtain robust confidence intervals, for the mean and median of differences (which estimate the bias). The statistical results seem to emphasize the interchangeability of both methods, although some lack of agreement. Medical researchers may use these simple and attractive approaches, namely using a spreadsheet program, which outputs (easily interpreted) might be useful in clinical judgment to decide whether agreement is acceptable or not.
Brief Biography of the Speaker: Luis Miguel Grilo (PhD in Mathematics and Statistics, Technical University of Lisbon, 2006) is currently Adjunct Professor and Director of the Department of Mathematics and Physics, as well as Director of Surveys and Statistical Studies Center of the Polytechnic Institute of Tomar (PIT) and of a Post Graduation in Computational Data Analysis. As a member of the Center for Mathematics and Applications of the New University of Lisbon (CMA UNL), develops scientific research in Distributions Theory (exact and near-exact distributions of some statistics used in Multivariate Analysis) and Statistics Applications (with special interest in Health). Publishes papers regularly in international scientific journals and has made several presentations at national and international meetings of Statistics, including as an Invited Speaker, receiving the "Best presentation award", in the PhD student category, with a paper presented at the International Conference on Statistics, Combinatorics and Related Areas and X Conference of the Forum for Interdisciplinary Mathematics (SCRA2003|FIMX), University of Southern Maine, USA. At the moment, is Academic editor of the British Journal of Mathematics & Computer Science, member of the Editorial Board of the Asian Journal of Mathematics and Computer Research and member of the board of CLAD (Portuguese Association of Classification and Data Analysis). As a member of Scientific and Organizing Committees, has participated in several national and international meetings of Statistics. In particular, in the PIT was the Chair of the International Conferences SCRA2006|FIM XIII, the XIX Conference on Classification and Data Analysis (JOCLAD2012), the 7th Workshop on Statistics, Mathematics and Computation (WSMC7, 2013) and the 5th International Conference on Risk Analysis (ICRA5, 2013).