title: Relative contributions of baseline patient characteristics and the choice of statistical methods to the variability of genotypic resistance scores: the example of didanosine.
abstract: BACKGROUND
  Our aim was to investigate the respective role of statistical methodology and patients' baseline characteristics in the selection of mutations included in genotypic resistance scores.
  
  
  METHODS
  As an example, the FORUM database on didanosine including 1453 patients was used. We split this population into four samples based on countries of enrolment (France n = 474, Italy n = 440, USA/Canada n = 219, others n = 320). We used both a continuous outcome measure (the viral load reduction at week 8) and a binary outcome measure (viral load decline at week 8 <0.6 log(10) or > or =0.6 log(10)) and both parametric and non-parametric methods for each outcome.
  
  
  RESULTS
  Overall, 61 distinct mutations were selected by at least one method in at least one data set. The variability due to baseline characteristics varies from 79% to 88%, i.e. for a given method applied to the four data sets >80% of the mutations are selected only once. The variability induced by the methodology varies from 49% to 56%, i.e. for a given data set approximately 50% of the mutations are selected by at least two methods.
  
  
  CONCLUSIONS
  Baseline patient characteristics contribute more than the choice of statistical method to the variability of the mutations to be included in the genotypic resistance scores.
authors.affiliation: INSERM, U943, Paris, F-75013 France. klassoumou@ccde.chups.jussieu.fr
authors.forename: Lambert
authors.initials: L
authors.lastname: Assoumou
authors.forename: Allal
authors.initials: A
authors.lastname: Houssaïni
authors.forename: Dominique
authors.initials: D
authors.lastname: Costagliola
authors.forename: Philippe
authors.initials: P
authors.lastname: Flandre
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000494:pharmacology*; D002170:Canada; D016049:Didanosine / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D005260:Female; D005602:France; D005838:Genotype; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D012367:RNA, Viral / Q000235:genetics*; D016896:Treatment Outcome; D014481:United States; D019562:Viral Load
chemical_list: D019380:Anti-HIV Agents; D012367:RNA, Viral; D016049:Didanosine