title: Adherence to Pre-Exposure Prophylaxis for HIV Prevention in a Clinical Setting.
abstract: BACKGROUND
  The HIV epidemic in the United States (US) disproportionately affects gay, bisexual, and other men who have sex with men (MSM). Pre-exposure prophylaxis (PrEP) using co-formulated tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) has demonstrated high efficacy in reducing HIV incidence among MSM. However, low adherence was reported in major efficacy trials and may present a substantial barrier to successful PrEP implementation. Rates of adherence to PrEP in "real-world" clinical settings in the US remain largely unknown.
  
  
  METHODS
  We reviewed demographic and clinical data for the first 50 patients to enroll in a clinical PrEP program in Providence, Rhode Island. We analyzed self-reported drug adherence as well as drug concentrations in dried blood spots (DBS) from patients who attended either a three- or six-month follow-up appointment. We further assessed drug concentrations and the resistance profile of a single patient who seroconverted while taking PrEP.
  
  
  RESULTS
  Of the first 50 patients to be prescribed PrEP, 62% attended a follow-up appointment at three months and 38% at six months. Of those who attended an appointment at either time point (70%, n = 35), 92% and 95% reported taking ±4 doses/week at three and six months, respectively. Drug concentrations were performed on a random sample of 20 of the 35 patients who attended a follow-up appointment. TDF levels consistent with ±4 doses/week were found in 90% of these patients. There was a significant correlation between self-reported adherence and drug concentrations (r = 0.49, p = 0.02). One patient who had been prescribed PrEP seroconverted at his three-month follow-up visit. The patient's drug concentrations were consistent with daily dosing. Population sequencing and ultrasensitive allele-specific PCR detected the M184V mutation, but no other TDF- or FTC-associated mutations, including those present as minor variants.
  
  
  CONCLUSIONS
  In this clinical PrEP program, adherence was high, and self-reported drug adherence accurately reflected drug concentrations as measured by DBS.
authors.affiliation: Division of Infectious Diseases, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Madeline C
authors.initials: MC
authors.lastname: Montgomery
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Oldenburg
authors.affiliation: Department of Behavioral and Social Sciences, Brown University School of Public Health, Providence, Rhode Island, United States of America.
authors.forename: Amy S
authors.initials: AS
authors.lastname: Nunn
authors.affiliation: Division of Infectious Diseases, University of Mississippi, Jackson, Mississippi, United States of America.
authors.forename: Leandro
authors.initials: L
authors.lastname: Mena
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Aurora, Colorado, United States of America.
authors.forename: Peter
authors.initials: P
authors.lastname: Anderson
authors.affiliation: Department of Medicine, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Teri
authors.initials: T
authors.lastname: Liegler
authors.affiliation: The Fenway Institute, Fenway Health, Boston, MA; Department of Medicine, Beth Israel Deaconess Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Mayer
authors.affiliation: Division of Infectious Diseases, Washington University, St Louis, Missouri, United States of America.
authors.forename: Rupa
authors.initials: R
authors.lastname: Patel
authors.affiliation: Division of Infectious Diseases, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Alexi
authors.initials: A
authors.lastname: Almonte
authors.affiliation: Division of Infectious Diseases, Brown University, Providence, Rhode Island, United States of America.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Chan
mesh_terms: D000293:Adolescent; D000328:Adult; D004305:Dose-Response Relationship, Drug; D059788:Dried Blood Spot Testing; D005260:Female; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy / Q000517:prevention & control*; D006801:Humans; D008297:Male; D055118:Medication Adherence; D008875:Middle Aged; D065129:Pre-Exposure Prophylaxis; D057566:Self Report; D000068698:Tenofovir / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D000068698:Tenofovir