title: Episodes of low-level viral rebound in HIV-infected patients on antiretroviral therapy: frequency, predictors and outcome.
abstract: BACKGROUND
  The rate, predictors and outcome following episodes of low-level viral rebound (LLVR) in HIV patients on highly active antiretroviral therapy (HAART) are unknown.
  
  
  METHODS
  Retrospective assessment of all HIV patients who experienced LLVR episodes on HAART at one institution from January 1999 to December 2006. LLVR was defined as plasma HIV-RNA between 51 and 500 copies/mL after at least two consecutive undetectable plasma viral load measurements made during the last 6 months. Virological failure was defined as plasma HIV-RNA >500 copies/mL.
  
  
  RESULTS
  Out of 2720 HIV patients on successful HAART during the 8 year study period, 779 (28.6%) developed at least one LLVR episode. Only 655 patients who kept unchanged their HAART regimen following LLVR episodes were further examined. After 12 weeks, undetectable viraemia was regained in 458 (71%), which were considered as blips. In contrast, 66 (9%) LLVR episodes were followed by virological failure, and drug resistance mutations developed in most cases, mainly rtM184V (66%) and rtK103N (29.5%). Plasma HIV-RNA remained between 51 and 500 copies/mL at 12 weeks in the remaining 131 (20%) patients with LLVR episodes. In the multivariate analysis, only plasma HIV-RNA levels at the time of LLVR predicted subsequent virological failure.
  
  
  CONCLUSIONS
  Episodes of LLVR in HIV patients on successful HAART are relatively common and represent transient events (blips) in most cases (71%). Keeping the same treatment regimen, virological failure follows in <10% of the cases. Plasma HIV-RNA level at the time of LLVR is the best predictor of subsequent failure.
authors.affiliation: Service of Infectious Diseases, Hospital Carlos III, Madrid, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: García-Gascó
authors.forename: Ivana
authors.initials: I
authors.lastname: Maida
authors.forename: Francisco
authors.initials: F
authors.lastname: Blanco
authors.forename: Pablo
authors.initials: P
authors.lastname: Barreiro
authors.forename: Luz
authors.initials: L
authors.lastname: Martín-Carbonero
authors.forename: Eugenia
authors.initials: E
authors.lastname: Vispo
authors.forename: Juan
authors.initials: J
authors.lastname: González-Lahoz
authors.forename: Vincent
authors.initials: V
authors.lastname: Soriano
mesh_terms: D000328:Adult; D023241:Antiretroviral Therapy, Highly Active / Q000639:trends*; D024882:Drug Resistance, Viral / Q000187:drug effects / Q000235:genetics; D005260:Female; D005500:Follow-Up Studies; D015658:HIV Infections / Q000188:drug therapy / Q000235:genetics / Q000821:virology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D016896:Treatment Outcome; D019562:Viral Load / Q000639:trends*