In this section, the inclusion of the participants in the KSPS is described first by looking back on relevant projects and surveys from Khayelitsha from 1999. Then the participants in the KPS are described by going through different surveys building up to the survey in 2007. A schematic overview of the participants included in KSPS and KPS is presented in the end (Figure 6).
KSPS
In 1999 Médecins Sans Frontières [MSF]20 started working in Khayelitsha to support the first provincial government-run project to prevent MTCT in South Africa (WHO, 2003c). In April 2000 MSF in cooperation with PAWC, set up three HIV/AIDS dedicated clinics within Khayelitsha’s primary health care centres. One year later the HIV/AIDS clinics began to offer ARVs free of charge to people in an advanced stage of HIV infection. Only patients who attended the HIV/AIDS clinics regularly or lived in Khayelitsha received ARVs (Coetzee, Boulle, et al., 2004). Furthermore only patients who had a CD4 count less than 200 cells/µl were offered ARVs. Between May 2001 and December 2002 a total of 287 patients got ARVs from the three clinics (Coetzee, Boulle, et al., 2004). The aim of the project by MSF was to show that treating HIV/AIDS with ARVs in a primary health care setting and in a resource-limited environment is feasible and replicable (WHO, 2003c).
In 2004 ASRU at UCT decided to try to survey as many people as possible who had received ARVs from the clinics. These people were soon included in the KSPS (also called Khayelitsha HAART Panel Survey) which then became a parallel panel survey to the KPS. The survey sample in the KSPS was recruited through social networks and contacts with clinics and support groups (Venkataramani, et al., 2010). People on ARVs were asked to volunteer and further asked to approach and suggest others they knew were on ARVs to volunteer. The sample method thus became in a sense a snowball sample. All together 242 patients receiving ARVs and living in Khayelitsha took part in the KSPS. Though the survey sample was not a random sample, the survey recruited more than two thirds of the patients who were the first to receive ARVs in 2001. Out of these, more than a third of those included in the survey were known to have been on ARVs for more than a year (Venkataramani, et al., 2010).
There were 224 respondents in the KSPS in 2005/2006 and 216 respondents in 2007. Lack of information made it impossible to get an overview of the reasons for attrition between the different waves.
20
MSF is an international, independent, medical humanitarian organization that delivers emergency aid to people affected by armed conflict, epidemics, healthcare exclusion and natural or man-made disasters.
KPS
The sample for the 2000 KMP survey was drawn to represent all adults in the Mitchell’s Plain Magisterial district. According to the 1996 Population census, there were 728.916 people living in the district. A two-stage cluster technique was chosen as the most cost-efficient method to interview residents representing such a large area and to obtain equal subsample sizes across the two stages of selection (Crankshaw, Welch, & Butcher, 2001; Magruder & Nattrass, 2005).
In the first stage clusters, households were selected based on the enumerator areas [EAs] defined by Statistics South Africa for the 1996 Population census, namely areas with neighbourhoods between 50 and 200 households. Before selecting EAs, all non-residential and institutional EAs (except hostels) were excluded. Then a random sample of EAs was drawn with probability of selection being proportional to population size. According to the 1996 Population census, the district consisted of 1486 populated EAs and the average number of adults per household was 2.66. The researches in the survey intended to administer 2875 questionnaires. Dividing the desired number of questionnaires (2875) by the average number of adults per household (2.66), it was determined that 1081 household should be selected. The target was further to interview at least 10 households from each selected EA. Dividing the number of household needed to reach the intended number of administered questionnaires (1081) by the number of households to be interviewed per EA (10), gave a total of 108 EAs. The 108 EAs were then listed in geographical order and by housing type which resulted in an implicit stratification of the sample by location and housing type. Forty-one of the EAs were in Khayelitsha.
In the second stage the households themselves were selected. The EAs were stored as digital data using Geographical Information Systems [GIS] technology21. Households were listed and a sampling interval was selected based on the number of households and an expected response rate of 80% to ensure that at least 10 households per EA were visited. 13 households were thus selected and all dwellings were listed always starting with the South-West corner. The first dwelling was selected on a random basis, and then subsequent households were selected according to the sampling interval. Supervisors were responsible for checking to see how many households there were in each dwelling to ensure that all households fell within the sampling frame.
21
This technology enables the boundaries of the different EAs to be superimposed on aerial images called orthophotos along with additional information such as street names. The 2000 KMP survey used orthophotos to
All adults aged 18 years and older in the selected households were interviewed. Households were revisited up to three times or more to obtain the necessary interviews. Some households in different EAs did not respond and not all individuals in selected households could be found or agreed to be interviewed. Still most of the individuals in sampled households were actually interviewed. For the entire KMP sample in 2000, 85% of selected households were found and agreed to let the interviewers through the door and the overall household response rate in Khayelitsha was 83%. The survey consisted of a total of 2644 individuals and of the respondents 69% were African, 30% were coloured and 1% were white and Indian people. Over half of African respondents in the survey (966 individuals) were living in Khayelitsha. Figure 5 gives an overview of the drawing of participants in the KMP survey.
Figure 5: Overview of the drawing of participants in the KMP survey
As noted earlier, the original KMP survey was not designed as a panel survey. Very little identification information was thus collected in 2000. Surnames were hardly ever collected and address information was often broadly descriptive. This was because in many informal settlement areas there was no adequate numbering system for dwellings. Fieldworkers in one of the informal settlement areas failed to find an entire EA through a combination of a poor aerial photograph
and the construction of new houses in the area. Though this resulted in some changes in the 2004 survey, the fieldworkers managed to find most of the households and were able to follow many of those who had moved within Khayelitsha. The response rate was thus reasonably good in the 2004 survey. Of the 966 potential Khayelitsha respondents in the KMP survey from 2000, 570 (60%) respondents were re-interviewed in 2004. Reasons for attrition between 2000 and 2004 were many and most were due to failure to interview the individuals. A total number of 373 could not be interviewed mainly because they had moved outside Khayelitsha (no address available) or had died. Another 23 potential respondents were lost due to survey management problems in the field. From the survey in 2004 to the survey in 2007, the number of respondents from Khayelitsha fell to 517. The reasons for attrition between the survey from 2004 to 2005/2006 and furthermore to 2007 was not available, but was most likely similar to the 2004 survey.