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Estimated sizes of Thai injection drug users (IDUs)

Estimated sizes of Thai injection drug users (IDUs). Apinun Aramrattana , MD, PhD Department of Family Medicine, Faculty of Medicine, Chiang Mai University, Administrative Committee on Substance Abuse A cademic Network, Thailand.

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Estimated sizes of Thai injection drug users (IDUs)

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  1. Estimated sizes of Thai injection drug users (IDUs) ApinunAramrattana, MD, PhD Department of Family Medicine, Faculty of Medicine, Chiang Mai University, Administrative Committee on Substance Abuse Academic Network, Thailand Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  2. Background • The previous estimate of IDU population size for Bangkok in 1991, using capture-recapture method, were 36,600 (Mastro et al, 1994). This was divided by 0.224 (1980-1999 Bangkok/Nationwide IDU-associated AIDS case ratio) to give a national estimate of 160,000 for 1980-1995 (Asian Epidemic Model, 2008). • In 2004 Wattanaet al., using RDS and multiplier methods to come up with Bangkok estimate of 3,595 IDUs. With the same method and additional assumptions, the national estimate was then calculated to be 38,380IDUs (Asian Epidemic Model, 2008). • In 2009, RDS and multiplier methods were • repeated in Bangkok and Chiang Mai. Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  3. Technical Consultation: Size Estimation of MARP in Asian Countries (23-5 September, 2013, Hong Kong ) Method I:RDS with multiplier Population-based data source: • Respondent-driven-sampling (RDS) surveys among IDUs in Bangkok (750) and Chiang Mai (300) conducted in 2009 • RDS can reach hidden and hard-to-reach populations (unlike venue-based sampling) • Cross-sectional survey • Included male and female IDUs injecting drugs in the past 6 months and aged 18 years or older Division of Global AIDS, CENTER FOR GLOBAL HEALTH Global AIDS Program Thailand and Asia Regional Office

  4. Technical Consultation: Size Estimation of MARP in Asian Countries (23-5 September, 2013, Hong Kong ) Methods (II) Institutional data source for Bangkok: • Tenofovir study (BTS) • High quality data (clinical trial) • Includes injectors of all drugs • Includes injectors both in and out of methadone treatment • High awareness of the study in IDU community Institutional data source for Chiang Mai: • Famai methadone clinic • Can differentiate injecting versus non-injecting users • Includes opiate injectors • Includes injectors in methadone treatment Division of Global AIDS, CENTER FOR GLOBAL HEALTH Global AIDS Program Thailand and Asia Regional Office

  5. Technical Consultation: Size Estimation of MARP in Asian Countries (23-5 September, 2013, Hong Kong ) Results (I) Estimating Size of IDU population in Bangkok – 2009 (n = 750) Division of Global AIDS, CENTER FOR GLOBAL HEALTH Global AIDS Program Thailand and Asia Regional Office

  6. Technical Consultation: Size Estimation of MARP in Asian Countries (23-5 September, 2013, Hong Kong ) Results (II) Estimating Size of IDU population in Chiang Mai – 2009 (n = 300) Division of Global AIDS, CENTER FOR GLOBAL HEALTH Global AIDS Program Thailand and Asia Regional Office

  7. Comparison: RDS (+ multiplier) vs Network Scale-up Number of all IDUs in RDS 2009, by districts (Chiang Mai, n=309) Estimation:(Opiate IDUs in the past 6 months) 1,500 (727-6000) RDS Recruitment site Any injections in the past 6 months NSUM household sample site Network Scale-up & Summation(Chiang Mai, 2009, n=409) Any injections in the past 2 years Estimation: (all IDUs) 2,260 – 4,012 Number of participants in districts 0 1-10 11-20 21-40 >40 Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  8. Technical Consultation: Size Estimation of MARP in Asian Countries (23-5 September, 2013, Hong Kong ) Method II:Network Scale-up Adapted from Guidelines on Estimation the Size of Populations Most at Risk to HIV, UNAIDS/WHO working group on Global HIV/AIDS and STI surveillance

  9. Network Scale-Up Method: Application in Thailand National MARP estimation, 2010, using network scale-up method m e • 4regions + Bangkok: Household survey • Using multi-stage sampling • Using 19-21 known populations in each region for estimating average ‘c’ • IDU size estimate (eIDU) = ( mIDU/c ) * t c t Technical Consultation: Size Estimation of MARP in Asian Countries (23-5 September, 2013, Hong Kong )

  10. e m c t Network Scale-Up Method: Application in Thailand To find C Approach 1: Network Scale-up approach 21 known populations applied:(2008) Birth, total, males, females 11. Village health volunteers Death, males, females 12. Kindergarten kids Unemployed, males, females 13. Primary school children Monks 14. Secondary school children Registered marriage 15. High school kids, males, females Registered divorce 16. Teachers in 1ry, 2ry & high school Elderly >79 years, males, females 17. Vocational students Foreigner, males, females18. University students Disabled, males, females 19. Physicians Traffic injured person 20. Nurses 21. University staffs Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  11. e m c t Network Scale-Up Method: Application in Thailand To find C Approach 2: Summation approach Generation of the categories: Small qualitative study on how people know others. 18 categories were used: People known from 1. Direct kinship 10. Schools 2. Relatives of father 11. Sporting activities 3. Relatives of mother 12. The Internet 4. Relatives of spouse 13. Public services 5. The same work unit 14. Recreation activities 6. Job networking 15. Service/business utilization 7. Neighbors 16. Political activities 8. Public/village meetings 17. The same ethnics route 9. Religious activities 18. The same social problem sufferings Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  12. e m c t Network Scale-Up Method: Application in Thailand What populations (m)? Definition? Most-at-risk populations (MARPs) , whom you have known in the past 2 years, 1. Men who have sex with men (MSM) Men,, who ever have sex with men in the past 2 years 2. Female sex workers (FSWs) Women,, who have ever sold sex in the past 2 years 3. Male sex workers (MSWs) Men,, who have ever sold sex in the past 2 years 4. Injection drug users (IDUs) Persons,, who have ever injected any drugs in the past 2 years 5. Migrant workers (MWs) Migrant workers,, who are Burmese, Laos and Cambodian Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  13. NSUM 2010: IDU estimates (e) as numbers x 1,000Total national size = sum of all regional sizes National IDU size estimates (e) = 40,300 – 97,300 Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  14. Comparison with National Household Survey, 2011 Asking directly to samples:Have you ever injected? Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  15. Conclusion: IDU size estimate for 2010-2011 National Household Survey on Substance Abuse, 2011 Method: Ask direct question ‘Have you ever injected drug?’ Results: Ever injected any drugs = 29,300 IDUs Asian Epidemic Model based on RDS study in Bangkok, 2004 Method: Assumptions 1: 30% underestimation Assumption 2: Bangkok/National AIDS case ratio can be a multiplier. Results: Any injections in the past 6 months = 38,300 IDUs Regional NSUM Survey, 2010 Method: Known population scale-up & Summation: Results: IDUs known in the past 2 years = 40,300 – 97,300 Consensus number (10 Jan. 2012) = 40,300 Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  16. National MARP estimation, 2010, using network scale-up method Network scale-up methods Strengths: • Representativeness at all levels can be achieved and repeatable. • It does not require members of hidden populations to identify themselves to a survey team. Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  17. National MARP estimation, 2010, using network scale-up method Strengths: • The questions can be incorporated into existing household surveys so estimates can be generated at the level of those surveys, typically national or provincial. • The method can create estimations for multiple hidden populations in one survey. Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  18. National MARP estimation, 2010, using network scale-up method Limitations: • Unable to obtain detailed risk behaviors and relevant biological markers • Barrier effect – some subgroups (eg. migrant workers) may not associate with members of the general population. • Transmission effect – A respondent may be unaware someone in his/her network engages in the behavior of interest (eg. injection, MSM, SW). Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  19. National MARP estimation, 2010, using network scale-up method Limitations: • Recall bias - There is a possibility that this may be over estimated as people may include those who “EVER” injected. • Results based on network scale up should be more conservative compared to summation. Known sub-populations provide better confidence than the plain summation. Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

  20. National MARP estimation, 2010, using network scale-up method Thanks.. • Prof. Russell Bernard & Prof. Christopher McCarty • UNAIDS/WHO • ACSAN & field teams • NAMC • All household samples • Global Funds Technical Consultation: Size Estimation of MARPs in Asian Countries (23-5 September, 2013, Hong Kong )

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