title: Poor performance of laboratories assaying newly developed antiretroviral agents: results for darunavir, etravirine, and raltegravir from the international quality control program for therapeutic drug monitoring of antiretroviral drugs in human plasma/serum.
abstract: BACKGROUND
  The International Interlaboratory Quality Control PROGRAM for Therapeutic Drug Monitoring of Antiretroviral Drugs in Human Plasma/Serum was initiated in 1999. We have previously published our experience during the first 10 years of the PROGRAM. Since 2010, 3 newly developed antiretroviral agents have been added to the
  
  
  METHODS
  darunavir, etravirine, and raltegravir. The objective of this analysis is to describe the performance of participating laboratories measuring these newer agents in 2011-2012.
  
  
  METHODS
  Each year, laboratories received 2 blind samples of human plasma/serum spiked with a low (<1.0 mg/L), medium (1.0-5.0 mg/L), or high (>5.0 mg/L) concentration of these drugs. Laboratory results were standardized to percentages with reference to the nominal (true) concentration. Any result that deviated more than 20% of the nominal values was defined as inaccurate.
  
  
  RESULTS
  The numbers of laboratories that participated by the end of 2012 were 44 for darunavir, 28 for etravirine, and 30 for raltegravir. A total of 357 results were evaluable for analysis. Of these, 64 (17.9%) results were reported with >20% deviation, so "inaccurate" (7.6% too low, 10.4% too high). The proportion of inaccurate results in 2011 was 21.3% for darunavir, 31.0% for etravirine, and 26.3% for raltegravir; in 2012, these figures improved to 8.1%, 23.2%, and 8.3% for darunavir, etravirine, and raltegravir, respectively. Taking darunavir as the reference, performance for etravirine was significantly lower [odds ratio = 0.462, 95% confidence interval: 0.246-0.866, P = 0.016] and performance for raltegravir was not significantly different. Low concentrations were significantly more frequently reported as inaccurate than medium or high concentrations: 28.6% versus 10.6% versus 8.8%, respectively (P < 0.001). Laboratories that used Liquid Chromatography with tandem Mass Spectrometry did not perform better than those using High Performance Liquid Chromatography/Ultrarapid Performance Liquid Chromatography: 41 inaccurate results in 200 samples (20.5%) versus 23 in 157 samples (14.6%, P = 0.154). Multiple logistic regression revealed that the concentration range was the only significant predictor of inaccurate results. The lower range of concentrations performed worse than medium or high concentrations (P < 0.001).
  
  
  CONCLUSIONS
  Laboratories continue to have problems with adequately measuring low plasma concentrations of antiretroviral agents. This is particularly a problem for some of the newer antiretroviral agents with plasma concentrations in the <1.0 mg/L range, such as etravirine and raltegravir.
authors.affiliation: *Department of Pharmacy, Radboud University Medical Centre, Nijmegen; and †Dutch Association for Quality Assessment in Therapeutic Drug Monitoring and Clinical Toxicology (KKGT), The Hague, The Netherlands.
authors.forename: David
authors.initials: D
authors.lastname: Burger
authors.forename: Stefanie
authors.initials: S
authors.lastname: Krens
authors.forename: Karen
authors.initials: K
authors.lastname: Robijns
authors.forename: Rob
authors.initials: R
authors.lastname: Aarnoutse
authors.forename: Roger
authors.initials: R
authors.lastname: Brüggemann
authors.forename: Daan
authors.initials: D
authors.lastname: Touw
mesh_terms: D044966:Anti-Retroviral Agents / Q000097:blood; D064790:Clinical Laboratory Services / Q000592:standards*; D000069454:Darunavir; D016903:Drug Monitoring / Q000592:standards*; D006801:Humans; D038622:Internationality; D009570:Nitriles; D011724:Pyridazines / Q000097:blood*; D011743:Pyrimidines; D011760:Pyrrolidinones / Q000097:blood*; D011786:Quality Control; D000068898:Raltegravir Potassium; D013449:Sulfonamides / Q000097:blood*
chemical_list: D044966:Anti-Retroviral Agents; D009570:Nitriles; D011724:Pyridazines; D011743:Pyrimidines; D011760:Pyrrolidinones; D013449:Sulfonamides; C451734:etravirine; D000068898:Raltegravir Potassium; D000069454:Darunavir