Table 5.

Examples of how to use the coronary artery calcium score to refine risk estimates.

Clinical scenario	Pre-test 10-year CHD risk estimate*	CAC score category	Proportion of CAC scores falling within the given category†	Post-test 10-year risk estimate for each CAC score category‡
				Conservative§	Optimistic§
60-year-old woman with hypertension and high cholesterol	15%	0:	0.47	9%	6%
		1–100:	0.36	15%	13%
		101–400:	0.12	25%	31%
		>400:	0.05	34%	51%
50-year-old man without other CHD risk factors	6%	0:	0.59	4%	3%
		1–100:	0.31	7%	6%
		101–400:	0.07	11%	15%
		>400:	0.03	16%	27%
40-year-old woman who smokes	3%	0:	0.89	2%	2%
		1–100:	0.10	4%	5%
		101–400:	0.01	7%	12%
		>400:	0.00	10%	22%
80-year-old man with high cholesterol	26%	0:	0.05	9%	5%
		1–100:	0.25	15%	10%
		101–400:	0.30	26%	23%
		>400:	0.40	35%	39%

* – From published Framingham equations [16].

† – These probabilities are calculated using regression equations presented in Tables 2 and 3 of this paper (full models with all predictors). See Methods for details.

‡ – Post-test risk estimates are calculated by assuming that the pre-test 10-year CHD risk estimate represents an average of persons with different CAC scores, weighted by the probability of having a CAC score in each category. The risk in each category is calculated algebraically using relative risk estimates§ from a recent meta-analysis [7] (see Additional File 1).

§-"Conservative" and "Optimistic" refer to assumptions made in a recent meta-analysis that attempted to quantify the value of CAC scores in predicting CHD events, independent of other CHD risk factors [7]. With conservative assumptions, relative risks associated with different CAC score categories were 1.7 (for CAC = 1–100), 3.0 (for CAC = 101–400) and 4.3 (for CAC>400) compared with a CAC score of zero. With optimistic assumptions, the corresponding relative risks were 2.1, 5.4, and 10.3.

CHD – Coronary heart disease; CAC score – Coronary artery calcification score.