final program.qxd - Parallels Plesk Panel

SS 1.4
HIV Resistance Testing in Clinical Practice: Comparative Analysis between
Genotypes and Virtual Phenotypes
L.Bocket-Mouton 1 , M.Lazrek 1 , H.Melliez 2 , C.Roussel 3 , F.Ajana 2 , D.Hober 1 , Y.Mouton 2 ,
Y.Yazdanpanah 2 .
1
Virology Department, Centre Hospitalier Universitaire de Lille, France
2
Infectious Diseases Department, Centre Hospitalier de Tourcoing, France
3
Virology Department, Centre Hospitalier Universitaire d'Amiens, France
Background
Drug resistance testing has become standard of care to guide antiretroviral treatment in
HIV-infected patients failing therapy. Several assays have been standardized to assess
HIV drug susceptibility: genotypes, phenotype or virtual phenotypes. The objective of this
study was to compare genotype resistance testing and vircotype ® HIV1 interpretation of
resistance in patients failing HAART.
Methods
66 heavily pre-treated HIV-infected patients experiencing virological failure were enrolled
in this study. In each patient, a genotype resistance testing using the ANRS
algorithm was performed based on the result of which a subsequent antiretroviral regimen
was initiated. Viral load decrease was determined 12 weeks after treatment initiation.
Virtual phenotype resistance tests were retrospectively performed in all patients. First we
compared genotype and virtual phenotype resistance mutations profiles. Results were
considered concordant or discordant (minor discordance=susceptible vs. intermediate or
intermediate vs. resistant; major discordance=susceptible vs. resistant). Next we looked
at viral load decrease at 3 months in those patients in whom drug were considered as
susceptible by genotype and resistant by virtual phenotype resistance testing.
Results
NNRTI susceptibility predictions were always concordant between the two tests. In NRTI
class, interpretation of the sequences showed concordance between the two systems in
15 patients (23%), but minor discordances in 21 patients (32%) and major discordances
in 30 patients (45%). In PI class, interpretation showed concordance in 20 patients (30%),
but minor discordances in 25 patients (38%) and major discordances in 21 patients (32%).
In 12 patients (18%) the two systems displayed major discordances in both NRTI and PI
susceptibility predictions. In 13 out of 16 patients in whom at least one drug was
considered susceptible by genotype resistance testing and resistant by phenotype
resistance testing, viral load decrease was