See
Hingorani AD, Vallance P. A simple computer program for guiding
management of cardiovascular risk factors and prescribing. BMJ
1999;318:101-5
uses the same formula as described below, and I believe Prof
Vallance is liaising with EMIS etc to make it available on UK primary
care systems. It's a shame the formula includes HDL cholesterol, I
feel, as this has not been routinely measured by our local lab until
recently. I would also like to be able to calculate the risk for
patients with established CHD.
Below are the spreadsheet instructions for the CVD risk equation used in
the most recent NZ blood pressure and lipid management guidelines.
These
are the instructions for completing an Excel spreadsheet.
Regards
Rod Jackson (faxed from computer)
Instructions for setting up a spread sheet to calculate CVD risk using a
Framingham equation.
Equation from: Anderson et al. CVD risk profiles. Am Heart J
1991;121:293-8.
CVD includes the following fatal and nonfatal events: MI, angina,
coronary
insufficiency, sudden and non sudden coronary death, stroke, TIA, PVD
(claudication), LVF (symptomatic).
I have used the fields A through Z and AA through AE to include the
necessary instructions. Once completed you can feed in any patient's
risk
factors (for the age group 35-75 years) and determine their probability
of
a CVD event over any period from 2-10 years.
Fields:
Risk factors:
A gender (female =1, male=0)
B age (years)
C SBP (mmHg)
D cigarettes (yes or stopped in last year=1, no=0)
E Total cholesterol (mmol/L)
F HDL cholesterol (mmol/L)
G diabetes (yes=1, no=0)
H ECG LVH (yes=1, no=0) note this is not the same as echo LVH which
is a lesser risk factor (echo is a more sensitive but less specific test
for LVH
Coefficients and equations:
I _0= 18.8144
J _1= -1.2146*(A)
K _2= -1.8443*LN(B)
L _3= blank
M _4= 0.3668*LN(B)*(A)
N _5= blank
O _6= -1.4032*LN(C)
P _7= - 0.3899*(D)
Q _8= -0.539*LN((E)/(F))
R _9= -0.3036*(G)
S _10= -0.1697*(G)*(A)
T _11= -0.3362*(H)
U _12= blank
V q1= 0.6536
W q2= -0.2402
X m= SUM((I):(T))
Y g= EXP((V)+((W)*(X)))
Z time (years) (I have set this at 5 years)
AA U= (LN(Z)-(X))/(Y)
AB probability of CVD = 1-EXP(-EXP(AA))
AC relative risk reduction (I have set at 0.33)
AD absolute risk reduction = (AB)*(AC)
AE NNT (numbers needed to treat for x years to prevent an event) =
1/(AD)
notes:
o LN is natural log
o EXP = exponential
o some of the coefficients are blank because other versions of the
same basic equation can be used for other endpoints and use additional
coefficients. I have set the spreadsheet up for these other endpoints
but
have just included the total CVD one here
o to check if the equation is written correctly use the following
example: woman, aged 60 years, SBP 160 mmHg, smoker, TC = 6mmol/L, HDL=
1.3mmol/L, diabetes, LVH, 5 year probability of CVD =38% (equation
reads
0.38014) , absolute risk reduction = 12.5% (equation reads 0.125446),
NNT=
8 (equation reads 7.97153)
Dr Francisco Machado,
Abersychan Surgery, Old Road, Abersychan, Torfaen, NP4 7BQ
website http://www.abersychan.demon.co.uk/home.htm
Dr Peter McCartney
Primary Care Research Group, Health Promotion Research Unit
Dept Public Health & Policy, London School of Hygiene and Tropical Medicine
Keppel Street, London WC1E 7HT
Tel 0171 927-2017 Fax 0171 637-3238 Mobile 0956 453018
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