Behavioural Surveillance Surveys - The Wisdom of Whores

Figure 5 : Example of cluster sampling for men who have sex with men
In 1992/93, an HIV seroprevalence and risk behavior survey was undertaken among homosexual
and bisexual men in the San Francisco Bay area. A variant of cluster sampling was used
in conducting the survey. Clusters or PSU’s for the survey consisted of locations or sites
frequented by young homosexual or bisexual men or by men who had sex with men but did not
identify themselves as homosexual or bisexual. The sites considered included street corners or
sidewalks, dance clubs, bars, and parks known to be frequented by such men. On the basis of
key community informant interviews and focus groups with groups of MSM, a total of 49 sites
were identified. Based upon direct observation and interviews with MSM found at each site, the
final list of sites to be included in the survey was reduced to 26 “high volume” sites, defined as
sites that yielded two or more eligible persons per hour during “peak” hours.
Interviewing was conducted during afternoons, evenings, and late at night. Intercept methods
were used in obtaining interviews with eligible respondents. Men appearing to be 22 years of
age or younger were approached at each site as they walked on the sidewalk, entered a venue,
or waited in line. Interviews (and for this particular survey ) blood drawing were conducted in
a specially equipped van parked near the sampling venue.
The target sample size was n=500 men. The sample was allocated to the 26 sites proportionally to
the expected number of eligible respondents per hour based upon information gathered during
the preliminary research phase. Data were collected during 96 visits to sample sites.
Source: Lemp et al., 1994.
Note: Although this example is for an HIV seroprevalence survey, as opposed to a behavioral
survey, it is often the case that sampling strategies for these different types of surveys can and
should be the same. Since blood samples are not to be taken in BSS surveys, having a van is not
necessary. Also note that the same proportional allocation would have resulted had the field
teams merely visited each site for the same amount of time (e.g., 2-3 visits per site for two hours
at a time)
Youth
The recommended sampling designs for
youth were not discussed in chapter Chapter 4,
partially because they follow more conventional
sampling methods. From a survey measurement
perspective, youth differ from the other groups
that might be covered in target group surveys
in that it is feasible to use repeated household
surveys to monitor changes in behavioral
indicators. In fact, a case may be made that
household surveys are the preferred way to go
about monitoring behavioral trends for youth
since such surveys can theoretically cover a
very high proportion of youth. Only youth
residing at school, or who have no fixed place
of residence (e.g., homeless or street children)
would be excluded from the universe of a
household survey. Note, however, that if in a
given setting a sizeable proportion of youth
fall into one of these categories and/or if there
are interventions planned or in place to
address such sub-groups, it might be necessary
to also survey them in addition to undertaking
household surveys.
B EHAV I OR A L S U R V EI L L A NC E SURV EY S APPEN DI X 3
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