INTRODUCTION:
Electron beam CT (EBCT) is an accurate,
noninvasive method to detect and quantify coronary artery
calcification, a marker of coronary artery disease (CAD). This
investigation examined the accuracy of EBCT to detect obstructive
CAD(>50% stenosis) and determined the optimal strata for
quantity of coronary artery calcification to facilitate clinical
decision-making.
METHOD:
Clinical research patients (n=213) were examined
with coronary angiography and EBCT (angiography group), and 765
research participants were examined with only EBCT (nonangiography group).
RESULTS:
Of the angiography group, 53% had obstructive CAD. After adjustment
for verification bias, the estimated sensitivity and specificity for
calcium score >1 were 97.0% and 72.4%, respectively. Likelihood
ratios for strata of calcium score associated with obstructive CAD
were calculated in each sex and 2 age groups. Among those >50
years old, the same 4 strata of EBCT calcium scores were identified
in each sex; likelihood ratios ranged from 0.03 (calcium score 0) to
12.85 (calcium score >200). The same 3 strata of EBCT calcium
scores were identified in each sex among those <50 years old;
likelihood ratios ranged from 0.13 (calcium score 0) to 190 (calcium
score >100).
CONCLUSION: A calcium score >200
among those >50 years old and calcium score >100
among those <50 years old provided strong evidence that patients
of either sex had obstructive CAD. A calcium score of 0 provided
strong evidence that patients >50 years old did not have
obstructive CAD.
COMMENTS by Dr
Peyser - Prior studies examined the accuracy of EBCT mostly in patients suspected
to have heart disease because of chest pain or other symptoms of heart disease
and have an estimated specificity of any calcium was less than 50%. This study
found the specificity to be about 70%. The researcher assigned subjects into
several group based on calcium scores and their age group. Since most people
older than 50 have detectable calcium levels in their arteries, it is important
that age-specific calcium scores be used to identify people with early signs of
heart disease. The authors recommend that a calcium
score of 200 or higher in those aged 50 or older be considered a sign that the
patient is very likely to have a partially blocked arteries. Similarly, a score
of 100 or higher among anyone younger than 50 should be taken as a sign that
further tests should be considered.
