CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 1, February 2012
6
AFRICA
for individuals with any combination of risk factors has been
developed.
16
While the 30-year risk equation provides a lifetime
risk level, it is thought that this method oversimplifies the risk
and may also lead to overuse of medication. Other limitations
of this method include patient-specific issues, such as socio-
economic status and ethnicity.
17
In Africa, large prospective studies to recalibrate these CVD
equations to correct for differences in baseline survival between
ethnic groups
18
are restricted by poor documentation of causes
of death as well as migration of individuals. The South African
adult population has high levels of CVD risk factors, and the
INTERHEART Study
19
showed that several of the risk factors for
myocardial infarction operate similarly in different ethnic groups
and geographical locations worldwide.
20
The aim of this pilot study was to assess the lifetime CVD risk
in the mixed-ancestry population of South Africa in individuals
with non-diabetic hyperglycaemia, undiagnosed diabetes, known
diabetes and normoglycaemia, using the recently developed
30-year CVD interactive risk calculator.
16
Methods
The Faculty of Health and Wellness Sciences Ethics Committee
of the Cape Peninsula University of Technology approved the
study, which was conducted according to the code of ethics of
the World Medical Association (Declaration of Helsinki). All
participants signed written informed consent after all the proce-
dures had been fully explained in the language of their choice.
In addition, permission was also sought from other relevant
authorities such as city and community authorities. These
authorities granted permission to operate in the community and
also to make use of designated places such as community halls
or nearby schools for data and sample collection.
Bellville South is located within the northern suburbs of Cape
Town, South Africa. It is traditionally a mixed-ancestry township
formed in the late 1950s. In the South African context, the term
township usually refers to the often underdeveloped urban living
areas that, under the Apartheid regime, were reserved for people
of mixed ancestry. According to the 2001 population census, its
population was approximately 26 758, with the people of mixed
ancestry making up 80.48% (21 536). The target population for
this study were subjects between the ages of 35 and 65 years and
their number was estimated to be 6 500.
21
Based on these statis-
tics and the recommended sample size for a pilot study, usually
10%, the sample size required for this pilot study was 650.
This was a cross-sectional study aimed at establishing a
cohort that could be followed up for insulin resistance and its
sequel in randomly selected mixed-ancestry subjects aged 35
to 65 years. The data presented here were collected from mid
January 2008 to March 2009. Using a map of Bellville South,
random sampling was approached as follows. From a list of
streets from each stratum, the streets were then classified as
short, medium and long streets based on the number of houses.
Streets with 22 or fewer houses were classified as short, streets
with 23–40 houses were medium, and long streets were those
with more than 40 houses. A total of 16 short streets represent-
ing approximately 190 houses, 15 medium streets representing
approximately 410 houses and 12 long streets representing
approximately 400 houses were randomly selected across the
different strata.
From the selected streets, all household members meeting
the selection criteria were eligible to participate in the study.
Community authorities requested that participants outside the
random selection area should benefit from the study. These were
also included, but given a different code.
Information regarding the project was disseminated to the
residents through the local radio station (Radio Tygerberg) and
community newspaper (the Tygerberger). Brochures and fliers
bearing information about the project were distributed via the
school children and taxis to the local residents. The recruitment
team consisted of unemployed matriculants and was managed
by a qualified, retired nurse from the community. Additionally,
a ‘road show’ strategy that involved a celebrity suffering from
diabetes from the same community was also used, especially in
the targeted streets.
Recruited subjects were visited by the recruitment team the
evening before participation and reminded of all the survey
instructions. The instructions included overnight fasting, and
abstinence from drinking alcohol or consumption of any fluids
on the morning of participation. Since the participants were
required to bring in an early morning mid-stream urine sample,
they were provided with a sterile container as well as instruc-
tions on how to collect the sample. Furthermore, participants
were encouraged to bring along their medical/clinic cards and/or
drugs they were currently using.
Data collection
A detailed protocol describing data-collection procedures (ques-
tionnaires and physical examination) was developed. The team
members, consisting of professional nurses and the recruitment
team, were trained and a pilot study in a neighbouring commu-
nity with similar demographics was performed to validate the
questionnaire and to synergise the workflow. A supervisor,
who monitored the performance of the personnel and who was
responsible for calibrating equipment according to a standard
protocol, was allocated to each team. In addition, a weekly meet-
ing was held to assess progress, solve problems and re-train the
research team.
A questionnaire designed to retrospectively obtain informa-
tion on lifestyle factors such as smoking and alcohol consump-
tion, physical activity, diet, family history of CVD and DM,
and demographics was administered by trained personnel. The
questionnaire was adapted from several existing standard and
recognised sources,
22,23
and was also pre-tested in a neighbouring
community with similar demographics. A detailed drug history
was obtained by interrogation and by examining the clinic cards
as well as the record of drugs that participants brought to the
study site.
Clinical measurements included height, weight, hip and
waist circumferences, body fat measurements (subscapular and
supra-iliac skin-fold thickness, triceps and mid upper-arm/biceps
circumference) and blood pressure. Qualified healthcare profes-
sionals who underwent training to standardise all measurements
prior to the commencement of the study carried out measure-
ments.
Blood pressure measurements were performed according to
WHO guidelines.
24
Measurements were performed using a semi-
automatic digital blood pressure monitor (Rossmax PA, USA)
on the right arm in a sitting and ambulatory position. After a
