The size estimation of injection drug users (IDUs) using the network scale-up method (NSUM) in Iranshahr, Iran

Background: The size estimation of key populations is a necessary part of surveillance systems to access global human immunodeficiency virus (HIV) infection. In this study, the NSU method was used to estimate injection drug users (IDUs). Methods: NSU method was performed on 1000 individuals in Iranshahr province with street-based sampling from 2016 to 2017. A questionnaire comprising items on demographic information and items measuring the network size of participants about IDUs was administered. The estimated size was adjusted for transmission error and barrier effect with PF and VF factors. The relationship between knowing IDUs and demographic variables was assessed using logistic regression. All analyses were performed in SPSS 19 and Microsoft Excel. Results: In this study, 500 men and 500 women were included. The average age (standard deviation) of the participants was 29.6 (7.8) years. IDUs were estimated at 1263 per 100 000 population of Iranshahr in Sistan and Baluchestan province, Iran. The estimated size was 7.5 times more in men than in women (2766 vs 364). Moreover, the highest estimated size belonged to the population of 18- 30-year-olds (1187). Sex and education level had significant relationships with knowing IDUs (p<0.001). Conclusion: To improve preventive programs, the number of outreach teams must be increased to have access to IDUs, educate them, and upgrade the coverage of harm-reduction services. According to cultural considerations and the illegal nature of injection drug use, social mobilization is essential to reduce the stigma.