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Session 94 Poster Abstracts
Resistance Predictors of Virologic Response and Clinical Outcome
Tuesday, 1:30 - 3:30 pm
Poster Hall


675
Genotypic vs Real Phenotypic Tests to Guide Salvage Antiretroviral Therapy in Heavily Pretreated Patients with Virological Failure: A 48 Weeks Prospective, Randomized Study (VIHRES Study)
J Blanco*1, A Guelar2, P Domingo3, E De Lazari1, G Valdecillo2, J R Arroyo3, A Biglia1, M Arnedo1, H Knobel2, T Pumarola1, J M Gatell1, and J Mallolas*1
1Hosp. Clin., Barcelona, Spain; 2Hosp. del Mar, Barcelona, Spain; and 3Hosp. Santa Creu i San Pau, Barcelona, Spain

Background:  The usefulness of resistance tests has rarely been tested during long periods of follow-up and focused in advanced failing population. Here we compare the role of genotypic and real phenotypic resistance tests in patients after multiple therapeutic failures, followed for 1 year.

Methods:  Patients failing on <2 previous HAART regimens (HIV RNA >5000 copies/mL) were randomized to guide their new HAART by either real phenotypic resistance tests (Antivirogram) (P arm), or genotypic resistance tests (G arm). An independent committee of a virologist and a clinician expert in interpreting resistance tests, and the treating clinician evaluated the report and decided the most convenient new regimen in each patient. The same resistance test could be performed at week 12 in patients not achieving ³1 log copies/ml and treatment reassessed by the same group of experts.

Results:  We randomized 137 patients (58 P arm, 78 G arm). Baseline characteristics were well balanced. The median number of previous HAART regimens were 4 and 3.5 in P and G arms, respectively. More than 45% had failed ³4 previous HAART regimens. At baseline viral load was 4,62 and 4,60 log and CD4 238 and 226 cells/mm3 in P and G arms, respectively. No statistical differences over 48 weeks of follow-up were found either by ITT (dropouts as failures) or by OT (dropouts as censored) analyses in terms of virological response. The percentages of patients with viral load <200 copies/mL over 48 weeks were, 38% in the P arm vs 28% in the G arm (p = 0.268) and 44% in the P and 41% in the G arm (p = 0.837), by ITT and OT analyses respectively. Median viral load reduction over 48 weeks was -1,60 and -1,65 log (p = NS) in P and G arms, respectively. Median change in CD4 cells over 48 weeks of follow-up were +3 (IQR:  -56;+69) in P arm and +14 (IQR:  -46; +88) in G arm (p = 0.485). Adherence (³95%) was a predictor of response in  both arms (OR 2,800; CI95 = 0,865 to 9,060; p = 0.086) and (OR 3,822; IC95 = 1,095 to 13,342; p= 0,036 ) in P and G arm respectively.

Conclusions: When expert advice was available real phenotype had no statistical significant advantage over genotypic resistance test in advanced failing patients.

Keywords: Genotypic vs Real Phenotypic; heavily pretreated patients; salvage therapy