2 diabetes) have been generated using information on the population Diabetes with renal disease. SBP 140 mm Hg, TC 7 mmol/l smoker, diabetes. 40 …
WHO/ISH Cardiovascular Risk Prediction Charts
Strengths and Limitations
Who is the target audience for these charts?
Among the 193 Member States of WHO, all high-income countries have
developed cardiovascular risk prediction charts using cohort data from
their own populations They have been refined over the years
Charts to predict the risk of heart attack or stroke do not exist for 160
WHO Member States The WHO/ISH risk prediction charts have been developed
from best available mortality and risk factor data of these low- and middle-
income country LMIC populations They are meant to be used in LMIC, where
refined risk prediction charts do not exist
What is the added value of these charts?
Almost 80 of the global epidemic of cardiovascular disease is already in
LMIC Individual and societal costs of premature deaths and disability and
escalating costs of medical care call for urgent measures to prevent and
control this epidemic in LMIC
Pragmatic and feasible approaches are needed to prevent people from getting
heart attacks and strokes Treating risk factors such as blood pressure and
blood lipids is one such approach However, this approach is
cost-effective
and affordable to most countries, only when targeted at high-risk
individuals
Further, currently individuals are often given drug treatment based on the
presence or absence of a single cardiovascular risk facto, such as high
blood pressure or high blood lipids Although this approach appears simple,
it can result in committing a patient with only a small cardiovascular risk
to many years of drug therapy or, conversely, neglecting to treat those
with an overall higher cardiovascular risk
Why not make the charts more accurate by using more variables?
The charts can have an impact on prevention of heart attacks and stroke,
particularly if they can be used by health-workers in primary health care
Health systems in LMIC do not have the basic infrastructure facilities to
support resource intensive risk prediction tools, particularly in primary
health care As charts use simple variables, they can be applied even in
low resource-settings
Using the chart, a health worker in PHC can select people at high-risk and,
if necessary, refer them for appropriate treatment to the next level of
care Thus, the WHO/ISH risk prediction charts and the accompanying
guidelines will
improve the effectiveness of cardiovascular risk
management, even in settings which do not have sophisticated technology
What is their added value?
Specialist physicians may not need risk prediction charts to broadly
categorize the level of risk of a person In many LMIC settings, non-
physician health-workers are the first contact for medical care A simple
tool of this nature will help them to assess the cardiovascular risk of
people rapidly, and take appropriate action
How have they been developed?
The charts have been developed using a modelling approach In brief, a set
of individual-level CVD risk factor profiles age, sex, systolic blood
pressure, total cholesterol, and the presence or absence of type -2
diabetes have been generated using information on the population
distribution of these risk factors from the WHO Comparative Risk Assessment
study These risk factor profiles have then been combined with information
on the relative risk of each risk factor, along with the population-level
estimate of absolute risk The risks of non-fatal and fatal myocardial
infarction and non-fatal and fatal stroke have been modelled and combined
to predict the individual risk of coronary
heart disease and
cerebrovascular disease
What are their limitations?
Due to the paucity of data, charts have been compiled not for individual
countries but for 14 WHO epidemiological sub-regions There are 28
different charts for 14 epidemiological sub-regions of WHO One set with
cholesterol and one set without cholesterol It is likely that results will
be most applicable to the largest country within the region The accuracy
and predictive value of current risk prediction charts need to be improved
as more epidemiological data becomes available from individual countries
If the charts are not perfect, is it safe to use them?
Charts are not perfect because of paucity and quality of available data
but they are safe for use for the intended purpose of broad risk
stratification
Only five categories of risk are depicted with five colours, four blood
pressure categories and five cholesterol categories are shown as they
should not be too complicated for use in the field Therefore, the charts
will not depict minor gradations in risk with precision
The best available data not as good as for high-income countries have
been used for developing the charts This is the best that can
be done for
LMIC populations for the moment It is a start We will be able to refine
the charts in the future, once cohort data hopefully are available for
individual populations
At present, these charts are necessarily crude but are safe and useful
tools for guiding the management and treatment decisions for individuals
When can treatment decisions be made without the charts?
As explained in the WHO guideline, the charts can underestimate the risk in
certain categories of people
eg Persistent raised blood pressure ?160/100 mm Hg or
Blood cholesterol ?8 mmol/l or
Established ischemic heart disease, or
Diabetes with renal disease
All of them need intensive lifestyle interventions and appropriate drug
therapy They do not need risk stratification using charts for treatment
decisions
When are the charts useful for stratifying risk?
Charts are useful for stratifying risk for people with blood pressure
160/100 mm Hg or blood cholesterol 8 mmol/l or uncomplicated diabetes
For example, by using the charts, person X and Y who have similar blood
pressures and l blood cholesterol levels can be correctly assessed for
their risk of developing a heart attack or a
stroke as follows:
| | |10 year risk |
| |Risk factor profile |of heart |
| | |attack or |
| | |stroke |
|Male X | |10 to | |
|50 years|SBP 140 mm Hg, TC 7 mmol/l, nonsmoker, no |20 | |
| |diabetes | | |
|Male Y | | | |
|50 years|SBP 140 mm Hg, TC 7 mmol/l smoker, diabetes |? 40| |
Person Y needs intensive lifestyle interventions and drug treatment to
prevent a heart attack or stroke
Person X needs lifestyle interventions and may need drug treatment if risk
persists at follow up
