IMPLEMENTATION SCIENCE Field Evaluation of Dried Blood Spots for HIV-1 Viral Load Monitoring in Adults and Children Receiving Antiretroviral Treatment in Kenya: Implications for Scale-up in Resource-Limited Settings Mary E. Schmitz, MPH,* Simon Agolory, MD,† Muthoni Junghae, PhD,* Laura N. Broyles, MD,† Muthusi Kimeu, MSc,‡ Joseph Ombayo, BSc,§ Mamo Umuro, MSc,§ Irene Mukui, MD,k Kennedy Alwenya, MA,‡ Moses Baraza, BSc,‡ Kenneth Ndiege, BSc,‡ Samuel Mwalili, PhD,* Emilia Rivadeneira, MD,† Lucy Ng’ang’a, MD,* Chunfu Yang, PhD,† and Clement Zeh, PhD, MPH,* for VL-DBS Study Group Background: The World Health Organization recommends viral load (VL) as the preferred method for diagnosing antiretroviral therapy failure; however, operational challenges have hampered the implementation of VL monitoring in most resource-limited settings. This study evaluated the accuracy of dried blood spot (DBS) VL testing under field conditions as a practical alternative to plasma in determining virologic failure (VF). Methods: From May to December 2013, paired plasma and DBS specimens were collected from 416 adults and 377 children on antiretroviral therapy for $6 months at 12 clinics in Kenya. DBSs were prepared from venous blood (V-DBS) using disposable transfer pipettes and from finger-prick capillary blood using microcapillary tubes (M-DBS) and directly spotting (D-DBS). All samples were tested on the Abbott m2000 platform; V-DBS was also tested on the Roche COBAS Ampliprep/COBAS TaqMan (CAP/CTM) version 2.0 platform. VF results were compared at 3 DBS thresholds ($1000, $3000, and $5000 copies/mL) and a constant plasma threshold of $1000 copies/mL. Results: On the Abbott platform, at $1000-copies/mL threshold, sensitivities, specificities, and kappa values for VF determination were $88.1%, $93.1%, and $0.82%, respectively, for all DBS methods, and it had the lowest percentage of downward mis- classification compared with higher thresholds. V-DBS performance on CAP/CTM had significantly poorer specificity at all thresholds (1000%–33.0%, 3000%–60.9%, and 5000%–77.0%). No significant differences were found between adults and children. Conclusions: VL results from V-DBS, M-DBS, and D-DBS were comparable with those from plasma for determining VF using the Abbott platform but not with CAP/CTM. A 1000-copies/mL threshold was optimal and should be considered for VF determina- tion using DBS in adults and children. Key Words: HIV, viral load, resource-limited settings, HIV RNA, dried blood spots, Kenya (J Acquir Immune Defic Syndr 2017;74:399–406) INTRODUCTION In 2016, the Joint United Nations Programme on HIV and AIDS (UNAIDS) reported that 17 million HIV-infected people worldwide were receiving antiretroviral therapy Received for publication July 9, 2016; accepted November 28, 2016. From the *US Centers for Disease Control and Prevention, Nairobi, Kenya; †US Centers for Disease Control and Prevention, Atlanta, GA; ‡Kenya Medical Research Institute, Nairobi, Kenya; §National HIV Reference Laboratory, Ministry of Health, Nairobi, Kenya; and kNational AIDS and STI Control Program, Ministry of Health, Nairobi, Kenya. Supported by the US President’s Emergency Plan for AIDS Relief (PEPFAR) through US Centers for Disease Control and Prevention, Division of Global HIV/AIDS under the terms of GH000041. L.N.B., M.J., M.E.S., S.A., I.M., L.N., Mwangi J, J.O., M.B., S.M., M.U., Akinyi J, Otecko N, E.R., C.Z., C.Y. Performance of Dried Blood Spot specimens prepared under field conditions to identify virologic failure among Kenyan children on antiretroviral therapy. Oral Presentation. 6th HIV Pediatrics Workshop. Melbourne, Australia. July 2014. Presenter: M.E.S. I.M., M.E.S., Katana A, M.K., Orwa J, Munguti C, Adega A, Vakil S, M.J., Okonji J, Kwaro D, Muttai, C.Z., S.M., E.R., S.A., L.N. Prevalence and determinants of virological failure among children on antiretroviral therapy in Kenya. Poster Presentation. 6th HIV Pediatrics Workshop. Melbourne, Australia. July 2014. M.E.S., S.A., M.U., M.J., J.O., L.N.B., I.M., K.A., Orwa J, Ouma K, Wagude J, S.M., L.N., C.Y., C.Z. Performance of Dried Blood Spots prepared under field conditions to identify virologic failure among adults and children on antiretroviral therapy in Kenya. Late-breaker poster presentation. International AIDS Conference. Melbourne, Australia. July 2014. M.B., K.A., S.A., Adega Anne, Fredrick Omondi, Jane Akinyi, M.E.S., J.O., M.J. Dried Blood Spots for Monitoring Virologic Failure: Healthcare Worker Preferences on Sample Collection Method. Oral Presentation. University of Nairobi Collaborative Meeting. Nairobi, Kenya. January 2015. Presenter: Fredrick Omondi. The authors have no conflicts of interest to disclose. The findings and conclusions in this article are those of the authors and do not necessarily represent the official position of the US Centers for Disease Control and Prevention or the Government of Kenya. The members of VL-DBS Study Group are listed in acknowledgments. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.jaids.com). Correspondence to: Mary E. Schmitz, MPH, Centers for Disease Control and Prevention, PO Box 606, Village Market, Nairobi 00621, Kenya (e-mail: uvy8@cdc.gov). Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. J Acquir Immune Defic Syndr  Volume 74, Number 4, April 1, 2017 www.jaids.com | 399 Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.