Determinants of coronary calcium conversion among patients with a normal coronary calcium scan: what is the "warranty period" for remaining normal?
OBJECTIVE
This study identified the incidence and predictors of conversion of a normal to abnormal coronary artery calcium (CAC) scan during serial CAC scanning over 5 years.


BACKGROUND
Although a normal CAC scan signifies absence of significant atherosclerosis and is used to identify individuals at low clinical risk, the "warranty period" of a normal CAC scan relative to its ability to predict sustained absence of coronary atherosclerosis remains unknown.


METHODS
We assessed frequency of and time to progression, as well as proportional increase of CAC in 422 individuals with normal CAC scan (CAC = 0) undergoing annual CAC scanning for 5 years. Results were compared with those of a referent cohort of 621 individuals with baseline CAC scan (CAC >0).


RESULTS
A total of 106 (25.1%) patients with CAC = 0 developed CAC during follow-up at a mean time to conversion of 4.1 +/- 0.9 years. Incidence of conversion to CAC >0 was nonlinear and was highest in the fifth year. In multivariable analysis, progression to CAC >0 was associated with age, diabetes, and smoking (p < 0.01 for all). Among the 621 individuals with baseline CAC >0, only the presence of CAC itself, rather than CAD risk factors, was predictive of CAC progression. Among propensity score-matched individuals with CAC >0 versus CAC = 0, baseline CAC >0 emerged as the strongest predictor of CAC progression (hazard ratio [HR]: 12.50, 95% confidence interval [CI]: 9.31 to 16.77), followed by diabetes (HR: 2.07, 95% CI: 1.47 to 2.90) and smoking (HR: 1.29, 95% CI: 1.02 to 1.63, p < 0.05 for all).


CONCLUSIONS
Among individuals with CAC = 0, conversion to CAC >0 is nonlinear and occurs at low frequency before 4 years. No clinical factor seems to mandate earlier repeat CAC scanning.
Min
James K
JK
Department of Medicine and Radiology, Weill Medical College of Cornell University, The New York Presbyterian Hospital, New York, New York 10021, USA. jkm2001@med.cornell.edu
Lin
Fay Y
FY
Gidseg
David S
DS
Weinsaft
Jonathan W
JW
Berman
Daniel S
DS
Shaw
Leslee J
LJ
Rozanski
Alan
A
Callister
Tracy Q
TQ
D002114:Calcinosis / Q000000981:diagnostic imaging*; D002118:Calcium / Q000378:metabolism*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D003331:Coronary Vessels / Q000378:metabolism*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D014057:Tomography, X-Ray Computed
D002118:Calcium