STRATEGIES FOR SAMPLING IDU FOR SURVEILLANCE Tasnim Azim Kolkata April 2007

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

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* B.Bridging Population Groups Truckers* Rickshawpullers Dockworkers Launch workers

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

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

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

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

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

RESPONDENT DRIVEN SAMPLING (RDS)

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

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

Wave 1 Wave 2 Wave 3 Wave 4 Wave 5

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)

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

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 SELECTION OF SEEDS

RESULTS Total number enrolled – 531

MSM: SELF CATEGORISATION %

Recruitment Chain of Seed#2 (N=111)

Recruitment Chain of Seed#3 (N=29)

Recruitment Chain of Seed#8 (N=5)

REACHING EQUILIBRIUM Calculated for nine variables

COMPARISON OF KEY VARIABLES BETWEEN DATA FROM BSS V ( ) AND RDS

Socio-demographic Characteristics RDSBSS V Mean age (in years) Mean income in last month (Tk.) Proportion who had no schooling19.50 Proportion currently married

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

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

IS RDS SUITABLE FOR SURVEILLANCE? 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

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