{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T08:56:05Z","timestamp":1777452965176,"version":"3.51.4"},"reference-count":46,"publisher":"SAGE Publications","issue":"3","license":[{"start":{"date-parts":[[2018,4,1]],"date-time":"2018-04-01T00:00:00Z","timestamp":1522540800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.sagepub.com\/page\/policies\/text-and-data-mining-license"}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Antiviral Therapy"],"published-print":{"date-parts":[[2019,4]]},"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>The real-world effectiveness of pre-exposure prophylaxis (PrEP) may be influenced by circulating HIV strains resistant to either tenofovir or emtricitabine. Yet, few studies have examined rates of resistance to these drugs in clinical settings.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We conducted a retrospective cohort study of antiretroviral-naive participants in the Canadian Observational Cohort collaboration who initiated antiretroviral therapy between 2006 and 2014. In separate analyses, we determined the prevalence of pretherapy resistance and cumulative incidence of follow-up resistance to tenofovir and emtricitabine. We used multivariable proportional hazards models to examine associations between baseline variables and the development of resistance.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      We studied 6,622 antiretroviral-naive participants initiating therapy, of whom 5,428 (82.0%) had a baseline resistance test. Baseline resistance to tenofovir and emtricitabine was observed in 83 (1.5%) and 21 (0.4%) patients, respectively. Among patients without baseline resistance, the cumulative incidence of resistance to tenofovir and emtricitabine 5 years following treatment initiation was 0.0070 (95% CI 0.0046, 0.0095) and 0.033 (95% CI 0.028, 0.038), respectively. Following multivariable analysis, a baseline viral load \u2265100,000 copies\/ml was associated with emergence of tenofovir (hazard ratio [HR] 2.88; 95% CI 1.35, 6.15) and emtricitabine (HR 2.27; 95% CI 1.64, 3.15) resistance. Initiating an integrase inhibitor-based regimen and CD4\n                      <jats:sup>+<\/jats:sup>\n                      T-cell count below 200 cells\/mm\n                      <jats:sup>3<\/jats:sup>\n                      were also associated with resistance to each drug.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>We observed a low prevalence of baseline resistance and a low incidence of emergence of resistance to tenofovir and emtricitabine among antiretroviral-naive patients in routine clinical care.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3851\/imp3302","type":"journal-article","created":{"date-parts":[[2019,3,15]],"date-time":"2019-03-15T05:43:27Z","timestamp":1552628607000},"page":"211-220","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":2,"title":["Tenofovir and Emtricitabine Resistance among Antiretroviral-Naive Patients in the Canadian Observational Cohort Collaboration: Implications for PrEP"],"prefix":"10.1177","volume":"24","author":[{"name":"The Canadian Observational Cohort Collaboration","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jaime","family":"Younger","sequence":"additional","affiliation":[{"name":"Toronto General Research Institute, University Health Network, Toronto, ON, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Janet","family":"Raboud","sequence":"additional","affiliation":[{"name":"Toronto General Research Institute, University Health Network, Toronto, ON, Canada"},{"name":"Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Leah","family":"Szadkowski","sequence":"additional","affiliation":[{"name":"Toronto General Research Institute, University Health Network, Toronto, ON, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Richard","family":"Harrigan","sequence":"additional","affiliation":[{"name":"Department of Medicine, University of British Columbia, Vancouver, BC, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sharon","family":"Walmsley","sequence":"additional","affiliation":[{"name":"Toronto General Research Institute, University Health Network, Toronto, ON, Canada"},{"name":"Department of Medicine, University of Toronto, Toronto, ON, Canada"},{"name":"Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada"},{"name":"CIHR Canadian HIV Trials Network, Vancouver, BC, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ahmed M","family":"Bayoumi","sequence":"additional","affiliation":[{"name":"Department of Medicine, University of Toronto, Toronto, ON, Canada"},{"name":"Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada"},{"name":"Centre for Urban Health Solutions, Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, ON, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marina B","family":"Klein","sequence":"additional","affiliation":[{"name":"CIHR Canadian HIV Trials Network, Vancouver, BC, Canada"},{"name":"Department of Medicine, McGill University Health Centre Research Institute, Montr\u00e9al, QC, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Curtis","family":"Cooper","sequence":"additional","affiliation":[{"name":"CIHR Canadian HIV Trials Network, Vancouver, BC, Canada"},{"name":"Ottawa Hospital Research Institute, Ottawa, ON, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ann N","family":"Burchell","sequence":"additional","affiliation":[{"name":"Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada"},{"name":"CIHR Canadian HIV Trials Network, Vancouver, BC, Canada"},{"name":"Centre for Urban Health Solutions, Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, ON, Canada"},{"name":"Department of Family and Community Medicine, St Michael's Hospital and University of Toronto, Toronto, ON, Canada"},{"name":"Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mona","family":"Loutfy","sequence":"additional","affiliation":[{"name":"Department of Medicine, University of Toronto, Toronto, ON, Canada"},{"name":"CIHR Canadian HIV Trials Network, Vancouver, BC, Canada"},{"name":"Women's College Research Institute, Women's College Hospital, Toronto, ON, Canada"},{"name":"Maple Leaf Medical Clinic, Toronto, ON, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mark","family":"Hull","sequence":"additional","affiliation":[{"name":"Department of Medicine, University of British Columbia, Vancouver, BC, Canada"},{"name":"CIHR Canadian HIV Trials Network, Vancouver, BC, Canada"},{"name":"British Columbia Centre for Excellence in HIV\/AIDS, Vancouver, BC, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alex","family":"Wong","sequence":"additional","affiliation":[{"name":"CIHR Canadian HIV Trials Network, Vancouver, BC, Canada"},{"name":"Division of Infectious Diseases, Department of Medicine, University of Saskatchewan, Regina, SK, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rejean","family":"Thomas","sequence":"additional","affiliation":[{"name":"Clinique M\u00e9dicale L'Actuel, Montreal, QC, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Robert","family":"Hogg","sequence":"additional","affiliation":[{"name":"CIHR Canadian HIV Trials Network, Vancouver, BC, Canada"},{"name":"British Columbia Centre for Excellence in HIV\/AIDS, Vancouver, BC, Canada"},{"name":"Faculty of Health Sciences, Simon Fraser University, Vancouver, BC, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Julio","family":"Montaner","sequence":"additional","affiliation":[{"name":"Department of Medicine, University of British Columbia, Vancouver, BC, Canada"},{"name":"British Columbia Centre for Excellence in HIV\/AIDS, Vancouver, BC, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chris","family":"Tsoukas","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, McGill University Health Centre, Montr\u00e9al, QC, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tony","family":"Antoniou","sequence":"additional","affiliation":[{"name":"Department of Family and Community Medicine, St Michael's Hospital and University of Toronto, Toronto, ON, Canada"},{"name":"Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada"},{"name":"Institute for Clinical Evaluative Sciences, Toronto, ON, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"179","published-online":{"date-parts":[[2018,4,1]]},"reference":[{"key":"bibr1-IMP3302","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1011205"},{"key":"bibr2-IMP3302","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(13)61127-7"},{"key":"bibr3-IMP3302","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1108524"},{"key":"bibr4-IMP3302","doi-asserted-by":"publisher","DOI":"10.1016\/S2352-3018(15)00206-4"},{"key":"bibr5-IMP3302","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(15)00056-2"},{"key":"bibr6-IMP3302","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1110711"},{"key":"bibr7-IMP3302","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1506273"},{"key":"bibr8-IMP3302","doi-asserted-by":"publisher","DOI":"10.1016\/S2352-3018(17)30089-9"},{"key":"bibr9-IMP3302","doi-asserted-by":"publisher","DOI":"10.1097\/QAD.0000000000001145"},{"key":"bibr10-IMP3302","unstructured":"World Health Organization. WHO expands recommendation on oral pre-exposure prophylaxis of HIV infection (PrEP). (Accessed 5 October 2018.) Available from http:\/\/www.who.int\/hiv\/pub\/prep\/policy-brief-prep-2015\/en\/"},{"key":"bibr11-IMP3302","doi-asserted-by":"publisher","DOI":"10.1097\/QAI.0000000000000172"},{"key":"bibr12-IMP3302","doi-asserted-by":"publisher","DOI":"10.1093\/infdis\/jit189"},{"key":"bibr13-IMP3302","doi-asserted-by":"publisher","DOI":"10.1128\/JVI.00843-11"},{"key":"bibr14-IMP3302","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMc1611639"},{"key":"bibr15-IMP3302","doi-asserted-by":"publisher","DOI":"10.1097\/QAI.0000000000001534"},{"key":"bibr16-IMP3302","doi-asserted-by":"publisher","DOI":"10.1016\/j.jcv.2016.08.293"},{"key":"bibr17-IMP3302","doi-asserted-by":"publisher","DOI":"10.2807\/1560-7917.ES.2017.22.11.30483"},{"key":"bibr18-IMP3302","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0080927"},{"key":"bibr19-IMP3302","doi-asserted-by":"publisher","DOI":"10.1093\/ije\/dyp393"},{"key":"bibr20-IMP3302","unstructured":"Department of Health and Human Services. 2006 Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. (Accessed 5 October 2018.) Available from http:\/\/aidsinfo.nih.gov\/guidelines\/archive\/adult-and-adolescent-guidelines"},{"key":"bibr21-IMP3302","doi-asserted-by":"publisher","DOI":"10.1016\/j.jviromet.2007.05.009"},{"key":"bibr22-IMP3302","doi-asserted-by":"publisher","DOI":"10.1159\/000332013"},{"key":"bibr23-IMP3302","doi-asserted-by":"publisher","DOI":"10.1097\/QAI.0b013e31816d9bf4"},{"key":"bibr24-IMP3302","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0109420"},{"key":"bibr25-IMP3302","doi-asserted-by":"publisher","DOI":"10.1002\/jmv.22047"},{"key":"bibr26-IMP3302","doi-asserted-by":"publisher","DOI":"10.1128\/JCM.06689-11"},{"key":"bibr27-IMP3302","doi-asserted-by":"publisher","DOI":"10.1097\/QAD.0000000000000203"},{"key":"bibr28-IMP3302","doi-asserted-by":"publisher","DOI":"10.1002\/sim.3618"},{"key":"bibr29-IMP3302","unstructured":"Public Health Agency of Canada. Update on HIV-1 Strain and Transmitted Drug Resistance in Canada: 2012\u20132013. Centre for Communicable Diseases and Infection Control, Public Health Agency of Canada, 2017. (Accessed 5 October 2018.) 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