What are the best tests to rule out cad?

No single test: A number of lab tests measuring lipids, hscrp, assess the risk for cad; exercise tests, angiography, radionucletotide scanning may help in detecting vascular lesions. As with any test there are false negatives and false positives.

The most accurate: is a heart cath - invasive, costly, occasionally causes problems - can't do that on everyone. all other tests are not as good. your doc chooses the most appropriate test on the basis of your pre-test risk determined by the clinical characteristics of your case. Early CAD is well detected by a "coronary calcium score" sometimes advertised as a heart scan.