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PBS Phase 3 Diabetes Population Prevalence Model
Background
The Yorkshire and Humber Public Health Observatory is the lead Public Health
Observatory for diabetes. In 2004, YHPHO was commissioned by the Department
of Health, in collaboration with the National Diabetes Support Team, to produce
a model that estimates total diabetes prevalence. The third and latest version
of the PBS model is now available from this website. It is the PBS Phase 3 Diabetes
Prevalence Model and it supersedes the Phase 2 and Phase 1 models.
PBS Diabetes Population Prevalence Model - Phase 3
Frequently Asked Questions
What is the PBS Diabetes
Population Prevalence Model?
What are the key
features of the updated PBS model Phase 3?What are the key features of the updated
PBS model Phase 3?
What are the potential uses
of the PBS model?
Why
include undiagnosed diabetes in estimates of diabetes prevalence?
Where do
the diabetes prevalence figures for the PBS model come from?
Where do the population
figures for the PBS model come from?
How
were the diabetes prevalence forecasts made?
Can I use my own population data and the PBS prevalence rates to calculate expected
numbers of cases at ward or general practice level?
What is the PBS Diabetes Population Prevalence Model?
This is a spreadsheet model that generates expected total numbers of persons
with Type 1 and Type 2 diabetes mellitus (diagnosed plus undiagnosed combined)
for 2005. Estimates are presented for England, Government Office Regions, Local
Authority Districts, Strategic Health Authorities, Primary Care Trusts and wards.
The model applies age/sex/ethnic group-specific estimates of diabetes prevalence
rates, derived from epidemiological population studies, to population estimates.
Estimates are also adjusted for geographic variations in socio-economic deprivation,
as a proxy for obesity. Forecasts of diabetes prevalence up to 2025 are presented
for sub-national areas based on projected population change and current trends
in obesity.
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What are the key features of the updated PBS model Phase 3?
New key features of the PBS Phase 3 model include:
- Diabetes prevalence estimates for 2005
- Diabetes prevalence forecasts for years 2010, 2015, 2020 and 2025 based
on predicted obesity trends and ONS population projections
- Estimates for current SHAs and PCTs
- Updated geographic deprivation adjustment based on the relationship
between diabetes registrations in the 2005/06 National Diabetes Audit and the
2007 Index of Multiple Deprivation
- Updated obesity adjustments based on Body Mass Index data from the Health
Surveys for England 1991 to 2006.
What are the potential uses of the PBS model?
The model can be used to compare expected prevalence between populations and
over time. Potential uses may include;
- Assessing the static completeness of diabetes registers in primary care
or assessing the completeness of case finding (proportion of all cases diagnosed)
- Comparing complication rates or admission rates after adjustment for
variation in expected prevalence
- Examining service provision and population need.
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Why include undiagnosed diabetes in estimates of diabetes prevalence?
The proportion of the population with undiagnosed Type 2 diabetes mellitus varies
widely. It is likely that the undiagnosed proportion has significantly decreased
in recent years due to the introduction of the Quality and Outcomes Framework
that promotes active case-finding and screening for high-risk populations. Asymptomatic,
but high-risk, populations that may be screened include people with vascular
disease (coronary heart disease, cerebrovascular or peripheral vascular disease)
and those with other risk factors for diabetes and vascular disease, such as
obesity, hypertension, family history and South Asian or Afro-Caribbean ethnic
origin.
If the total number of expected cases predicted by the model is compared with
the number of diagnosed cases from QOF this will give an indication of the proportion
of cases still unrecorded and potentially undiagnosed. It will also give an
indication of the potential impact of screening activity i.e. the size of the
potential pool of cases that might be identified by a screening programme.
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Where do the diabetes prevalence figures for the PBS model come from?
As no single study could be found that provides diabetes population prevalence
rates for all ethnic groups, for both Type 1 and Type 2 diabetes mellitus, the
model combines prevalence rates taken from a number of UK studies.
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Where do the population figures for the PBS model come from?
The 2005 estimates were made using an Office for National Statistics (ONS) commissioned
table of 2005 mid-year population estimates by broad ethnic-group, sex and quinary
age-group (Experimental Statistics). Forecasts for the years 2010 to 2025 used
ONS 2004 based sub-national population projections by sex and quinary age-group
customised with 2005 ethnic-group proportions.
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How were the diabetes prevalence forecasts made?
Forecasts of 2010, 2015, 2020 and 2025 diabetes prevalence are presented for
England, GORs, LADs, SHAs and PCTs. The forecasts use sub-national population
projections and therefore account for anticipated changes in population size
and age distribution. The forecasts are also adjusted by an index which reflects
predicted levels of obesity in England and the associated levels of diabetes
that would be expected to arise in the forecast years. The index is based on
an extrapolation of obesity levels recorded by the Health Survey for England
between 1991 and 2006.
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Can I use my own population data and the PBS prevalence rates to calculate expected
numbers of cases at ward or general practice level?
Yes, there are two options for doing this;
- If you have the population split by ethnic group, sex and age-group for the
local population in which you are interested, you can calculate diabetes prevalence
rates using exactly the same method as used for the pre-calculated rates. You
will also need to input the percentages of the population in deprivation quintiles
based on the Indices of Deprivation 2007.
- If you only have the population split by sex and age you can calculate the
total diabetes prevalence rate and number of persons with diabetes. You will
also need to input the Asian and Black percentages of the population and select
the ward in which the majority of the population resides to apply an appropriate
deprivation adjustment. This option is designed for General Practice populations.
Superseded releases of the PBS model
PBS Diabetes Population Prevalence Model - Phase 2
The PBS Phase 2 Diabetes Prevalence Model is now superseded by the PBS Phase
3 Diabetes Prevalence Model. The phase 2 model has been made available as much
of the supporting documentation is also relevant to the Phase 3 model
PBS Diabetes Population Prevalence Model - Phase 1
The PBS Phase 1 diabetes prevalence model is now superseded by the PBS Phase
2 and PBS Phase 3 diabetes prevalence model. The phase 2 model additionally
includes a deprivation adjustment and should always be used in preference to
the Phase 1 model. The phase 1 model has been made available on this website
because phase 1 results have been published in the Diabetic Medicine journal,
and those reading this article may find it useful to access the phase 1 model.