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rds’ implementation in vietnam: experience and lessons learned

rds’ implementation in vietnam: experience and lessons learned. The 2 nd Global HIV/AIDS Surveillance Meeting Bangkok, Thailand March 2-5, 2009. Nguyen Anh Tuan, PhD National Institute of Hygiene and Epidemiology. Historical background. 15 surveys used RDS method were conducted in Vietnam

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rds’ implementation in vietnam: experience and lessons learned

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  1. rds’ implementation in vietnam: experience and lessons learned The 2nd Global HIV/AIDS Surveillance Meeting Bangkok, Thailand March 2-5, 2009 Nguyen Anh Tuan, PhD National Institute of Hygiene and Epidemiology

  2. Historical background 15 surveys used RDS method were conducted in Vietnam • In 2004: • Two surveys in Female Sex Workers (FSW) (WV) • Three surveys in Injecting Drug Users (IDU) (CDC) • In 2005: (IBBS round I) • Four surveys in IDUs • Two surveys in MSMs • In 2006: (Pilot study in implementing new approaches in sentinel surveillance) • Two surveys in IDUs • Two survey in FSWs

  3. Why RDS were used? • Methods of time location sampling (TLS) could not be applied in the provinces being very hard to reach target populations such as FSW, IDU, and MSM: • Did not have enough budget and staff to conduct mapping phase in order to apply TLS methodology • Had a mapping in order to do TLS, but target population did not participate in the study through the invitation of interviewers to visiting study site. • Locations that members of target population congregate were not representative for the population • Participants can talk more “true” in answering the questions of the surveys at safer study site

  4. Why RDS were used? • To evaluate whether RDS for conducting HIV sentinel surveillance (HSS) are feasible and produce information as good as or better than current HSS methods for IDUs and FSWs: • It was very difficult to select “real” FSWs and to call the participation of IDUs in taking blood in the current sentinel surveillance • To avoid the risk in visiting the field to collect the blood samples in the “unsafe conditions” for medical workers • To use as “recapture” phase in capture-recapture methodology in estimating the size of target population

  5. experiences and lessons learned

  6. Should Conduct Formative Research • Use existing information (peer educators, public health staff, health care providers, HIV/AIDS case reporting) • In-depth interviews were useful for gathering qualitative data from members of the target population. • Focus group discussions were used to gather information on social networks and to pretest survey questions and methodological issues • Formative research can help: • Decide whether RDS is an appropriate sampling method for the population being studied • Identify subpopulations of interest and help select subsets for seeds • Identify individual seeds • Define logistical issues (proper incentive, study sites, locations, etc.) • Materials development: coupons, survey questions, forms

  7. In Selecting seeds • Seeds should be selected through social mapping of target population networks and sub-networks • Selecting seeds that were as diverse as possible with regard to sub-networks • Relevant characteristics were included such as age, geography, drug use, social status, economic status, etc. • Seeds need to be well motivated, as their primary utility is as recruiters • Number of seed should be 3-5

  8. Management and distribution coupons • Coupons’ managers (2 for 1 site) should be trained about method of management and of distribution coupons: • How to coding the coupons • Fill-day-out forms for coupon distribution • Receive the coupons coming back from new recruits. • Interview the recruiters about the persons who refuse to participate • How to pay for interviewer and recruiter • Coupon should be designed two parts: • One for paying incentive to recruiter • One for keeping by study • Two incentive for one participant: • Direct pay to recruiter after interview • Pay recruiter based on the numbers of recruitees that they invited sucessfully (visited the study sites and participated in the study).

  9. Coupon Components – Front Coupon Given to Peer Stub for Reward

  10. Coupon Components – Back Information Extra information for the Peer Extra Information for the Recruiter

  11. Linking recruiters and recruitees • For analysis purposes, it is crucial to know who recruited who, as well as ordering in recruitment chain • This was done via use of numbered coupons and Excel spreadsheets: • There were 7 digits in the coding number if we wanted to reach 5 waves in maximum: Coding number = N0.N1.N2.N3.N4.N5 N0 = 2 digits, seed number in the survey, N1 = 1 digit, number 1-3, representative for 1st wave N2 = 1 digit, number 1-3, representative for 2nd wave N3 = 1 digit, number 1-3, representative for 3th wave ……. With the number: 02.1.2.1.1.0 from seed number 2, recruit number 1 of first wave, recruiter number 2 of second wave, …

  12. Coding for the new recruits (5 waves)

  13. Verifying eligibility As respondents were rewarded for being interviewed in RDS, participant have tendency to receive more incentive by being interviewed multiple times under different identities • To avoid: • Study sites should not excess 2 • Started in the first site with 2 coupons’ managers • Finished at the first site and moved to second site with the same 2 coupons’ managers.

  14. Measuring non-response bias A questionnaire on the invited persons but refuse to participate was completed in the survey • But it was not used: • Recruiter did not tell about story of all refusal (it take more time, no more incentive) • Coupons did not come sometime directly from recruiter: recruiter gave to some one and they gave or sold to others.

  15. Measuring network size • Having a measure of personal network size is essential in order to be able to properly weight the data • Question on network size was included in the survey questionnaire • Accuracy of reported network size ?

  16. Advantages of RDS • Reach less visible portion of “hidden” sub-populations: call girl, indirect FSW, call girl on the internet, new IDU, … • It is easier for interviewer – target members do the recruitment for them • Good if conduct biological testing – having good place to take specimens

  17. Limitations of RDS • Management demanded strictly and complicated • Need to keep track of links between recruiters and recruitees • Need to verify sub-population membership • Need to verify pre-existing relationship between recruiter and recruitees • Need to control non-response bias • Need to use special software to do the analysis. This software is not easy to use and limited analysis • Remaining methodological concerns requiring further discussions • Validity of key assumption that people recruit at random within their personal networks?

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