This calculator recalculates the 10-year heart disease risk determined by the Framingham scoring system according to the EBT Coronary Calcium Score. This calculator uses a modified Bayes theorem and these sensitivities (SE) and specificities (SP) for EBT coronary calcium scores greater than 0, 80, 400 and 600 for the prediction of cardiac events.

for CAC Scores > 0:SE0 = 98%SP0 = 30%
for CAC Scores > 80:SE80 = 81%SP80 = 72%
for CAC Scores > 400:SE400 = 36%SP400 = 94%
for CAC Scores > 600:SE600 = 24%SP600 = 97%

'R' is the Framingham score event risk, the formula for the combined risks are:
Risk CAC(0) = aR + b(R(1-SE0))/[(R(1-SE0))+((100-R)SP0)] x 100)
Risk CAC(1-80) = aR + b(R(SE0-SE80))/[(R(SE0-SE80))+(100-R)(SP80-SP0)] x 100)
Risk CAC(81-400) = aR + b(R(SE80-SE400)/[(R(SE80-SE400))+(100-R)(SP400-SP80)] x 100)
Risk CAC(401-600) = aR + b(R(SE400-SE600)/[(R(SE400-SE600))+(100-R)(SP600-SP400)] x 100)
Risk CAC(>600) = aR + b(R(SE600)/[R(SE600)+((100-R)(1-SP600))] x 100)

Where a + b = 1;  a & b factor in the information overlap between the Framingham score and the CAC score.  Since both the Framingham scorerisk and CAC scores rise with increasing age and male sex, they are not true independent variables and strict Bayesian rules do not apply.