Impact of therapeutic drug monitoring of antiretroviral drugs in routine clinical management of patients infected with human immunodeficiency virus and related health care costs: a real-life study in a large cohort of patients

Background: Highly active antiretroviral therapy (HAART) has reduced morbidity and mortality in patients infected with human immunodeficiency virus (HIV). Studies have documented high interindividual variability in the pharmacokinetics of antiretroviral drugs, which may impair the success of HAART if not managed properly. Therapeutic drug monitoring (TDM) is a useful diagnostic tool that helps clinicians to optimize drug doses so that drug concentrations associated with the highest therapeutic efficacy are obtained with a reduced risk of concentration-dependent adverse effects. The aim of this study was to assess whether use of TDM improves clinical outcomes and cost of illness. Methods: A retrospective cohort study was conducted at L Sacco University Hospital in Milan, Italy, in HIV-infected patients aged $18 years with at least one prescription of antiretroviral drugs for which TDM was applied. The inclusion period was from January 2010 to December 2011, with a follow-up period of up to 12 months. Laboratory and administrative databases were analyzed and matched with each other. Results: The cohort consisted of 5,347 patients (3,861 males and 1,486 females) of mean age 43.9 +/- 12.5 years. We found that TDM had been used in 143 of these patients, among whom adherence with therapy was significantly higher than among those in whom TDM had not been used (94% versus 78%). In TDM-controlled patients, the mean length of HIV-related hospitalization stay and mean cost of hospitalization were significantly reduced with respect to those observed in the group in which TDM had not been used (7.21days versus 29.47days and is an element of 293 versus is an element of 688, respectively). Conclusion: Inclusion of TDM as part of routine clinical optimization of drug dosing in HIVinfected patients is associated with higher adherence to therapy, reduced length of hospitalization stay, and reduced cost of illness.