title: A mixed model for repeated dilution assays.
abstract: We propose a generalized linear mixed model to estimate and test marginal effects on titers repeatedly measured by serial dilution assays. The link is log-log and the titer is assumed to follow a gamma distribution. The parameters are estimated by generalized estimating equations. The marginal effects are tested by means of Wald and score tests, using the robust estimator of the variance. This approach avoids the problems arising from assays leading to nonestimable individual titers. Simulations were used to compare the Wald and score tests to Wilcoxon and Student t-tests. This method is applied to the comparison of the antiviral efficiency of three treatments against HIV.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Villejuif, France. bloch@vjf.inserm.fr
authors.forename: J
authors.initials: J
authors.lastname: Bloch
authors.forename: M
authors.initials: M
authors.lastname: Chavance
mesh_terms: D019380:Anti-HIV Agents / Q000627:therapeutic use*; D016049:Didanosine / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D006678:HIV / Q000302:isolation & purification; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy* / Q000821:virology; D006801:Humans; D015233:Models, Statistical; D015337:Multicenter Studies as Topic; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D019562:Viral Load; D016047:Zalcitabine / Q000627:therapeutic use; D015215:Zidovudine / Q000627:therapeutic use
chemical_list: D019380:Anti-HIV Agents; D015215:Zidovudine; D016047:Zalcitabine; D016049:Didanosine