{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,21]],"date-time":"2026-09-21T15:49:42Z","timestamp":1790005782269,"version":"4.0.1"},"reference-count":32,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2023,1,31]],"date-time":"2023-01-31T00:00:00Z","timestamp":1675123200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["ascpt.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Clin Pharma and Therapeutics"],"published-print":{"date-parts":[[2023,4]]},"abstract":"<jats:p>Tenofovir diphosphate (TFVdp; an active metabolite of oral HIV pre\u2010exposure prophylaxis (PrEP)) is measured in dried blood spots (DBS) to estimate adherence. However, TFVdp's long half\u2010life in whole blood may lead to misclassification following a recent change in adherence. PrEP's other metabolite, emtricitabine triphosphate (FTCtp), has a shorter half\u2010life in whole blood but adherence thresholds are undefined. We characterized DBS TFVdp and FTCtp concentrations across many dosing scenarios. Population pharmacokinetic models were fit to TFVdp and FTCtp DBS concentrations from a directly observed therapy study (NCT03218592). Concentrations were simulated for 90\u2009days of daily dosing followed by 90\u2009days of 1 to 7 doses\/week and for event\u2010driven PrEP (edPrEP) scenarios. Thresholds of 1,000 and 200 fmol\/punch, for TFVdp and FTCtp, respectively, were reflective of taking 4 doses\/week (a minimum target for effective PrEP in men). TFVdp was &lt;\u20091,000 fmol\/punch for 17\u2009days after initiating daily PrEP and &gt;\u20091,000 fmol\/punch for 62\u2009days after decreasing to 3 doses\/week. Respectively, FTCtp was &lt;\u2009200 fmol\/punch for 4\u2009days and &gt;\u2009200 fmol\/punch for 6\u2009days. Accuracy of edPrEP adherence classification depended on duration between last sex act and DBS sampling for both measures with misclassification ranging from 9\u2013100%. These data demonstrate adherence misclassification by DBS TFVdp for 2\u2009months following a decline in adherence, elucidating the need for FTCtp to estimate recent adherence. We provide proof of principle that individualized interpretation is needed to support edPrEP adherence monitoring. Our collective approach facilitates clinicians' ability to interpret DBS results and administer patient\u2010centric interventions.<\/jats:p>","DOI":"10.1002\/cpt.2845","type":"journal-article","created":{"date-parts":[[2023,1,9]],"date-time":"2023-01-09T12:57:21Z","timestamp":1673269041000},"page":"896-903","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["A Novel Algorithm to Improve PrEP Adherence Monitoring Using Dried Blood Spots"],"prefix":"10.1111","volume":"113","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2778-3725","authenticated-orcid":false,"given":"Aaron S.","family":"Devanathan","sequence":"first","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3500-5819","authenticated-orcid":false,"given":"Julie B.","family":"Dumond","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9509-6978","authenticated-orcid":false,"given":"Daijha J.C.","family":"Anderson","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kristen","family":"Moody","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amanda J.","family":"Poliseno","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amanda P.","family":"Schauer","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Craig","family":"Sykes","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cynthia L.","family":"Gay","sequence":"additional","affiliation":[{"name":"University of North Carolina School of Medicine  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5531-7281","authenticated-orcid":false,"given":"Elias P.","family":"Rosen","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Angela D.M.","family":"Kashuba","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"},{"name":"University of North Carolina School of Medicine  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mackenzie L.","family":"Cottrell","sequence":"additional","affiliation":[{"name":"University of North Carolina Eshelman School of Pharmacy  Chapel Hill North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2023,1,31]]},"reference":[{"key":"e_1_2_10_1_1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1108524"},{"key":"e_1_2_10_2_1","doi-asserted-by":"publisher","DOI":"10.1097\/QAI.0000000000001143"},{"key":"e_1_2_10_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/S1473-3099(14)70847-3"},{"key":"e_1_2_10_4_1","doi-asserted-by":"publisher","DOI":"10.1016\/S2352-3018(21)00071-0"},{"key":"e_1_2_10_5_1","doi-asserted-by":"publisher","DOI":"10.1097\/QAI.0000000000000158"},{"key":"e_1_2_10_6_1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1402269"},{"key":"e_1_2_10_7_1","unstructured":"Landovitz R. 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