title: Predictors of a viral response and subsequent virological treatment failure in patients with HIV starting a protease inhibitor.
abstract: OBJECTIVE
  To investigate the factors related to viral load becoming undetectable among patients from Southern Alberta who started a protease inhibitor for the first time, and to determine the factors related to subsequent re-emergence of detectable viral load amongst those patients whose viral load initially became undetectable.
  
  
  METHODS
  A total of 243 patients from the Southern Alberta Clinic had started a protease inhibitor for the first time and had been followed up for a median time of 32 weeks. Standard survival techniques including Kaplan-Meier techniques and Cox proportional hazards models were used to determine which factors were related to viral load becoming undetectable.
  
  
  RESULTS
  At 24 weeks after first exposure to a protease inhibitor, 52.8% of the patients [95% confidence interval (Cl), 45.2-56.6] had achieved an undetectable viral load. In a multivariate analysis, those with a higher initial viral load were less likely to become undetectable [relative hazard (RH), 0.50; 95% Cl, 0.35-0.70; P < 0.0001], whereas those starting more new drugs (RH per new drug, 1.54; 95% Cl, 1.01-2.11; P = 0.048) were significantly more likely to achieve an undetectable viral load. Amongst 111 patients whose viral load became undetectable, Kaplan-Meier analysis indicated that 15.5% of patients experienced re-emergence of detectable viral load at 24 weeks after the first undetectable viral load. A higher CD4 cell count was associated with a lower risk of viral load becoming detectable (RH, 0.73; 95% Cl, 0.53-1.00; P = 0.049), as was treatment with indinavir (versus any other protease inhibitor RH, 0.17; 95% Cl, 0.03-0.86; P = 0.033).
  
  
  CONCLUSIONS
  A significant proportion of patients in a routine clinic setting achieved an undetectable viral load measurement after first starting a protease inhibitor; viral load in patients with a higher CD4 cell count was more likely to become and stay undetectable. There was no evidence that patients who were drug-naive experienced significantly worse virological effects than drug-experienced patients, as long as the same number of new drugs was started at the date of first exposure to a protease inhibitor. Further follow-up of these patients is warranted to study the longer term effects of treatment with protease inhibitors.
authors.affiliation: Royal Free Centre for HIV Medicine and Department of Primary Care and Population Sciences, Royal Free and University College London Medical School, UK.
authors.forename: A
authors.initials: A
authors.lastname: Mocroft
authors.forename: M J
authors.initials: MJ
authors.lastname: Gill
authors.forename: W
authors.initials: W
authors.lastname: Davidson
authors.forename: A N
authors.initials: AN
authors.lastname: Phillips
mesh_terms: D000328:Adult; D018791:CD4 Lymphocyte Count; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006678:HIV / Q000302:isolation & purification; D015658:HIV Infections / Q000188:drug therapy*; D017320:HIV Protease Inhibitors / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D019562:Viral Load
chemical_list: D017320:HIV Protease Inhibitors