1 / 42

STRATEGIES FOR SAMPLING IDU FOR SURVEILLANCE

STRATEGIES FOR SAMPLING IDU FOR SURVEILLANCE. Tasnim Azim Kolkata April 2007. SECOND GENERATION SURVEILLANCE FOR HIV IN BANGLADESH Since 1998. Serological component – HIV, syphilis Behavioural component. National AIDS/STD Programme Directorate General of Health Services

duy
Download Presentation

STRATEGIES FOR SAMPLING IDU FOR SURVEILLANCE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. STRATEGIES FOR SAMPLING IDU FOR SURVEILLANCE Tasnim Azim Kolkata April 2007

  2. SECOND GENERATION SURVEILLANCE FOR HIV IN BANGLADESH Since 1998 Serological component – HIV, syphilis Behavioural component National AIDS/STD Programme Directorate General of Health Services Ministry of Health and Family Welfare Govt. of the People’s Republic of Bangladesh

  3. VULNERABLE POPULATION GROUPS • A. Those most vulnerable • Injecting drug users (IDU) • Heroin smokers • Sex workers – • female, street, brothels, hotels, casual* • male, street • hijras, street • Men having sex with men (MSM, non sex workers) • Babus from brothels* • Sex partners of Hijras* • Bridging Population Groups • Truckers* • Rickshawpullers • Dockworkers • Launch workers

  4. A concentrated epidemic in Bangladesh, 2006 Injecting Drug Users 18 cities sampled for IDU, HIV found in four cities only Concentrated epidemic in Central city A % NASP, 2006 Surveillance data

  5. Proportion of IDU reporting borrowing last week and exposure to the NSP last year % % Behavioural Surveillance, NASP Surveillance data

  6. Male IDU: Borrowing during the last week (among those who injected in the last week)

  7. EXISTING SAMPLING METHODOLOGIES • TIME LOCATION SAMPLING (TLS) - Behavioural • CONVENIENCE SAMPLING - Serological

  8. LIMITATIONS OF EXISITNG METHODOLOGIES • WHO ARE WE REACHING? – the most visible • LACK OF INTEGRATION OF SERO AND BSS • HOW REPRESENTATIVE IS OUR DATA?

  9. RESPONDENT DRIVEN SAMPLING (RDS)

  10. ADVANTAGES OF RDS • Does not require a sampling frame • Allows access to the more hidden people within marginalized population groups • Integration of behavioural and serological surveillance is possible

  11. Some key features of RDS • Chain referral method that starts with a set of non-randomly selected seeds • RDS methodologies are not conducted in the field but in a fixed location • Requires providing incentives

  12. Wave 1 Wave 2 Wave 3 Wave 4 Wave 5

  13. Wave 1 Wave 2 Wave 3 Wave 4 Wave 5

  14. Wave 1 Wave 2 Wave 3 Wave 4 Wave 5

  15. Wave 1 Wave 2 Wave 3 Wave 4 Wave 5

  16. Wave 1 Wave 2 Wave 3 Wave 4 Wave 5

  17. Wave 1 Wave 2 Wave 3 Wave 4 Wave 5

  18. The theory behind RDS • Given sufficiently long referral chains (i.e. 5-6 waves), the sample composition becomes stable regardless of the person or persons you start with • This means that with respect to key characteristics and behaviors, the composition of the final sample will be independent of who is selected as “seeds” • It also means that the final sample will be similar to the population-at-large that you are recruiting from (i.e. male IDUs who have been injecting in the last year)

  19. Piloting of Respondent Driven Sampling (RDS) for Integrated HIV and Behavioural Surveillance among Males who have Sex with Males (MSM) in Dhaka National AIDS/STD Programme Directorate General of Health Services Ministry of Health and Family Welfare Govt. of the People’s Republic of Bangladesh ICDDR,B IEDCR

  20. SELECTION OF SEEDS • Were selected from different background – • ·self categorisation (kothi, panthi, gay, etc) • ·NGO involvement • ·occupational background (e.g. students, artists, NGO participants, etc) • Eight seeds were selected – four were exposed to intervention programmes and the other four were not

  21. RESULTS Total number enrolled – 531

  22. MSM: SELFCATEGORISATION %

  23. Recruitment Chain of Seed#2 (N=111)

  24. Recruitment Chain of Seed#3 (N=29)

  25. Recruitment Chain of Seed#8 (N=5)

  26. REACHING EQUILIBRIUM Calculated for nine variables

  27. COMPARISON OF KEY VARIABLES BETWEEN DATA FROM BSS V (2003-2004) AND RDS

  28. Socio-demographic Characteristics

  29. Prevalence of HIV and Syphilis (comparison with 7th round serological surveillance)

  30. SUMMARY OF COMPARISONS BETWEEN DATA FROM RDS AND BSS • RDS accessed more diverse and hidden individuals • Diverse categorisations • Non-cruising sites • Not exposed to interventions • Active syphilis rates obtained are different (although not statistically significant) from that obtained from the serological surveillance • Differences observed in risk behaviours between RDS and BSS • Less risk reported in RDS in terms of proportions of MSM having sex and number of sex partners • Higher risk reported in RDS as condom use lower

  31. PROS Access to more diverse and MSM who are not involved with interventions Integration of serological surveillance and BSS possible Easier to check quality of data No sampling frame required CONS Separate discreet set-up required Coupon tracking not always easy Analysis complicated RDSAT (analysis tool) not user friendly May be difficult to check duplication IS RDS SUITABLE FOR SURVEILLANCE?

  32. Which method(s) - how to decide? • Each country has to weigh its own pros and cons • Different methodologies may be suitable for different groups • RDS requires social networking and IDU have strong networks • Cost implications – international data suggest RDS may be cheaper

More Related