Time – Location Sampling
Description
This course aims to provide participants with practical skills and knowledge to implement a population-based bio-behavioural HIV survey using Time Location Sampling (TLS). TLS is a widely used method to sample populations that are “floating” (i.e. are less likely to be found by researchers at the fixed place of residence), such as injecting drug users at shooting galleries, truck drivers at bus stop, sex workers at street corners etc. TLS is a venue-based sampling that is based on the clusters, and can achieve a high degree of generalisability. In TLS, a primary-sampling unit is defined as the combination of the site and the time, and the same site may be included in the sampling frame more than once, at different times of the day or a week. It has been used to sample different high risk groups and results have been described in the literature.
Learning objectives
The course will describe the requirements, principles and design of a survey which uses TLS in a variety of field contexts. Presenters will describe all the steps necessary for organising and implementing a TLS survey. Important issues to be covered include conducting mapping and development of a sampling frame and randomization, establishing collaboration with high-risk groups and the communities, the selection of venues for inclusion in the sampling frame, organization of the study, enumeration, screening participants for eligibility, roles and responsibilities of staff, data management and documentation and collection of biological and behavioral data. Issues in weighting TLS data will be discussed and demonstrated in STATA. Furthermore, this course provides field examples of the advantages and challenges associated with implementing TLS and provide contingency plans for dealing with difficult and unforeseen problems in the field.
Key topics
When to implement time-location sampling
How to do mapping, randomization and sampling calendar
Enumeration and recruitment into the survey
Study design issues in time-location sampling
Team composition
Study documentation and duration of the survey
Transfer of data, weighting and data analysis
HIV and STI tests
Advantages and disadvantages of time-location sampling
Key references:
Ferreira LO, de Oliveira ES, Raymond HF, Chen SY, McFarland W. Use of Time-location Sampling for Systematic Behavioral Surveillance of Truck Drivers in Brazil. AIDS Behav. 2008 Apr 5.
van Griensven F, Thanprasertsuk S, Jommaroeng R, Mansergh G, Naorat S, Jenkins RA, Ungchusak K, Phanuphak P, Tappero JW. Bangkok MSM Study Group. Evidence of a previously undocumented epidemic of HIV infection among men who have sex with men in Bangkok, Thailand. AIDS 2005; 19: 521-6.
Muhib FB, Lin LS, Stueve A, Miller RL, Ford WL, Johnson WD, Smith PJ. Community Intervention Trial for Youth Study Team. A venue-based method for sampling hard-to-reach populations. Public Health Rep 2001;116 Suppl 1: 216-22
Stueve A, O'Donnell LN, Duran R, San Doval A, Blome J. Time-space sampling in minority communities: results with young Latino men who have sex with men. Am J Public Health 2001; 91: 922-6
MARPS – Sampling strategies and design tools
United States Department of Health and Human Services, Centers for Disease Control and Prevention, Global AIDS Program Surveillance Team
http://www.theagencyfordesign.com/clients/cdc/sampling-methods/time-location-sampling.html
Teaching Methods
The course consists of lectures, exercises and a design of a surveillance protocol based on time-location sampling. Exercises will include practicing randomization of venues selected into the sampling frame, enumeration and recruitment of participants in the survey. Data management and analysis will be done on computers.
Target Audience
Participants may include epidemiologists, statisticians and HIV programme managers who work on HIV surveillance. High-level statistical or epidemiological training is not a prerequisite.
Duration:
The course takes place in five days.
Partners:
San Francisco Department for Public Health
Downloads:
Programme: Training course in Time-location sampling
