Contents lists available at ScienceDirect International Journal of Drug Policy journal homepage: www.elsevier.com/locate/drugpo Research Paper Evaluation of the treatment failure ratio in individuals receiving methadone maintenance therapy via the network scale up method Zeynab Heydari a , Mohammad Reza Baneshi b , Hamid Sharifi c , Maryam Zamanian d , Saiedeh Haji-Maghsoudi e , Farzaneh Zolala f, ⁎ a Neuroscience Research Center, Kerman University of Medical Sciences, Kerman, Iran b Modeling in Health Research Center, Institute for Futures Studies in Health, Kerman University of Medical Sciences, Kerman, Iran c HIV/STI Surveillance Research Center, and WHO Collaborating Center for HIV Surveillance, Institute for Futures Studies in Health, Kerman University of Medical Sciences, Kerman, Iran d Department of Epidemiology, School of Health, Arak University of Medical Sciences, Arak, Iran e Department of Biostatistics & Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran f Social Determinants of Health Research Center, Institute for Futures Studies in Health, Kerman University of Medical Sciences, Kerman, Iran ARTICLE INFO Keywords: Methadone MMT Network scale up Treatment failure ABSTRACT Background: The network scale up (NSU) method is an indirect size estimation method that has received re- markable attention in estimating the sensitive behaviors. Using methadone maintenance therapy (MMT), which is a treatment for opioid use disorder, is a sensitive topic in many societies. The aim of this manuscript was to estimate the number of MMT users and its failure ratio using the NSU method in the city of Kerman, Iran, in 2016. Methods: In this cross-sectional study, 1275 men and 1275 women which were aged > 18 years and who had lived in the city of Kerman for at least 5 years were recruited via multistage sampling. Data was collected via face-to-face interviews using a questionnaire that was included questions for estimating the network size of the residents of Kerman as well as the number of MMT users and the existing failure among them. Results: In total, the average network size of the citizens of Kerman was 235; among them, 97 were men and 138 were women. Overall, the numbers of MMT users and failures were estimated at about 5289 and 2731, re- spectively, leading to a failure ratio about 52%. The treatment failure ratio in the women and men was equal to 55% and 51%, respectively. Among the men, the failure ratio in all age groups was equal to ˜50%. Among the women, the failure ratio in those who were aged < 18 years was equal to 76%. Conclusion: The considerable failure ratio indicates the need for conducting studies on MMT services in order to understand the reasons which exist regarding this failure. This is of particular importance in specific groups, such as in young women. Further, the comparable results with other direct methods indicate that the NSU method could be used in the size estimation of MMT failure ratios. Introduction The network scale up (NSU) method, which is an indirect method of size estimation, has received a growing attention in estimating the sensitive and hidden behaviors such as usage of drugs (Bernard et al., 2010), Prostitution (Salganik et al., 2011) and abortions (Rastegari et al., 2014). These behaviors are hidden due to religious, cultural, or law restrictions against them (Ezoe, Morooka, Noda, Sabin, & Koike, 2012). Drug usage in many societies is highly stigmatized; therefore, any action indicating usage of drugs, including services for drug treatment, is concealed (Semple, Amaro, Strathdee, Zians, & Patterson, 2009). Among different methods of drug treatment, methadone main- tenance therapy (MMT) has been widely used in many countries for the treatment of drug use and harm reduction (WHO, 2017). In order to evaluate an MMT program, correct data is needed. However, many individuals who use drugs are reluctant to disclose their addiction or usage of services related to the treatment of drug addiction (Castle, 2004). Therefore, data which are gained from formal registration systems and direct methods of data collection are more https://doi.org/10.1016/j.drugpo.2019.07.022 ⁎ Corresponding author. E-mail addresses: heidariz66@yahoo.com (Z. Heydari), rbaneshi2@gmail.com (M.R. Baneshi), saharifihami@gmail.com (H. Sharifi), maryam_zamanian23@yahoo.com (M. Zamanian), sa.maghsoudi@gmail.com (S. Haji-Maghsoudi), F.zolala@kmu.ac.ir (F. Zolala). International Journal of Drug Policy 73 (2019) 36–41 0955-3959/ © 2019 Elsevier B.V. All rights reserved. T