Behavioural Surveillance Surveys - The Wisdom of Whores

found at the various locations at different
times. This last piece of information is needed
to help determine the cluster size, that is the
number of people it will be possible to sample
from each PSU (time-location cluster). Once
the information has been gathered, it is then
possible to construct a sampling frame
consisting of time-location segments, which
are used as PSU’s.
Parental consent for youth
It is worth mentioning that although oral
informed consent from respondents is routine
practice for BSS surveys, in some settings,
when working with young people, under the
age of 18 years or so, it is necessary also to
obtain parental consent. The necessity for this
is highly variable, depending on locally accepted
research practices, and the guidelines of those
who are funding the research. If parental
consent is required, it is important to take
steps to minimize the bias that this might
potentially cause. At a minimum, even if
parents would like to review the contents of
the questionnaire before it is administered,
it is best if the interview itself be conducted
outside the earshot of parents. It is also a
good idea to track the refusal rate of parents,
in order to assess how much non-response
bias might be influencing the results.
Obviously in the case of street kids, it will not
be possible to obtain parental consent.
Mobile populations
Mobile populations are of concern for HIV/
AIDS programs because of their potential for
engaging in risky behavior. Transportation
workers, for example, often spend extended
period of time away from home, and the
frequency of engaging in casual sexual
relationships buying sex from sex workers is
probably higher than in the general population
in most settings. Migrant laborers also work
away from home, in factories, plantations and
mining towns, to name a few. Merchants who
import and export also travel frequently, both
domestically and internationally.
The general recommended sampling
approach for mobile populations is similar to
that of other floating populations. The only
major difference lies in the nature of the “sites”
to be used as PSU’s for cluster sampling.
Appropriate sites or PSU’s for long distance
transportation workers could be truck stops,
depots or customs checkpoints, hotels where
mobile populations congregate in significant
numbers.
The initial step is the development of a
sampling frame of sites where such persons
congregate. This will require consultation
with key informants and members of the
population. In compiling the list of sites,
attention should be paid to ensuring that the
sampling frame covers all geographic parts of
the survey universe. Once a list of establishments
has been developed, time location
sampling units should be created for use as
PSU’s. For example, if 20 truck stops were to
be identified and if truck stops were to be
open seven days per week, a total of 140
PSU’s would be created. Note, however,
that if preliminary research were to indicate
that different types of transportation workers
frequented truck stops during the daylight
hours than at night, PSU’s might be further
divided into day-night segments, yielding a
total of 280 PSU’s. As for the other subpopulations,
the list of PSU’s should be ordered
geographically and (if relevant) by type of site
prior to sample selection.
334
A PPEN DI X 3 B EHAV I OR A L SURV EI L L A NC E S U R V EY S