The MESA website has some useful online tools for estimating arterial age and age and sex percentile calcium scores. Check them out here.
The UK's NICE committee has also produced a PDF that explains the concept of using calcium scoring in subjects with chest pain of recent onset.
Lifetime cardiovascular risk (as opposed to 10 year risk) is another approach, suggested by Berry and colleagues in the NEJM.
A lifetime risk calculator can be found here - QRisk website.
Useful tool from the Confirm CT registry that integrates coronary CTa findings with clinical risk factors and demographic data - Confirm Tool.