• An alternative classification to mixture modeling for longitudinal counts or binary measures

      Subtil, F; Boussari, O; Bastard, M; Etard, J-F; Ecochard, R; Génolini, C (SAGE Publications, 2014-09-01)
      Classifying patients according to longitudinal measures, or trajectory classification, has become frequent in clinical research. The k-means algorithm is increasingly used for this task in case of continuous variables with standard deviations that do not depend on the mean. One feature of count and binary data modeled by Poisson or logistic regression is that the variance depends on the mean; hence, the within-group variability changes from one group to another depending on the mean trajectory level. Mixture modeling could be used here for classification though its main purpose is to model the data. The results obtained may change according to the main objective. This article presents an extension of the k-means algorithm that takes into account the features of count and binary data by using the deviance as distance metric. This approach is justified by its analogy with the classification likelihood. Two applications are presented with binary and count data to show the differences between the classifications obtained with the usual Euclidean distance versus the deviance distance.
    • Combined Interventions to Reduce HIV Incidence in KwaZulu-Natal: A Modelling Study

      Blaizot, S; Huerga, H; Riche, B; Ellman, T; Shroufi, A; Etard, J; Ecochard, R (BioMed Central, 2017-07-26)
      Combined prevention interventions, including early antiretroviral therapy initiation, may substantially reduce HIV incidence in hyperendemic settings. Our aim was to assess the potential short-term impact of combined interventions on HIV spreading in the adult population of Mbongolwane and Eshowe (KwaZulu-Natal, South Africa) using sex- and age-specific scenarios, and age-targeted interventions.
    • Potential Impact of Multiple Interventions on HIV Incidence in a Hyperendemic Region in Western Kenya: a Modelling Study

      Blaizot, S; Maman, D; Riche, B; Mukui, I; Kirubi, B; Ecochard, R; Etard, JF (BioMed Central, 2016-04-29)
      Multiple prevention interventions, including early antiretroviral therapy initiation, may reduce HIV incidence in hyperendemic settings. Our aim was to predict the short-term impact of various single and combined interventions on HIV spreading in the adult population of Ndhiwa subcounty (Nyanza Province, Kenya).
    • Response to antiretroviral therapy: improved survival associated with CD4 above 500 cells/μl.

      Maman, D; Pujades-Rodriguez, M; Nicholas, S; McGuire, M; Szumilin, E; Ecochard, R; Etard, J-F; Epicentre, 8 rue saint Sabin, Paris, France; bHospices Civils de Lyon, Service de Biostatistique, cUniversite´ de Lyon, Lyon, France; Me´decins Sans Frontie`res, Paris, France. (2012-07-17)
      We investigated the association between immune response and mortality in four HIV African programs supported by Médecins Sans Frontières.