NICE further recommends that the pre-test probability of CAD determines the need (or otherwise) for further investigation as follows :
|CAD probability <10%||Consider an alternative diagnosis|
|CAD probability 10-29%||Offer CT coronary calcium scoring as the first line diagnostic investigation|
|CAD probability 30-60%||Offer functional imaging as the first line diagnostic investigation|
|CAD probability 61-90%||Offer invasive coronary angiography as the first line diagnostic investigation|
|CAD probability >90%||Begin treatment for angina without further testing|
These recommendations have significant implications for the UK NHS which is currently not appropriately set up to investigate these patients in this way. In particular, NICE does not recommend the use of Exercise ECG testing (which is currently the most commonly used functional test) as the functional test for patients with intermediate probability of CAD (30-60%) as it is diagnostically inferior to other functional tests such as myocardial perfusion scanning, stress echocardiography and magnetic resonance perfusion scanning. Exercise ECG testing still has a role as a functional test in patients who are known to have CAD and who present with chest pain.
NICE also recommends the use of novel investigations such as CT coronary calcification in lower (10-29%) risk patients because, if negative, it has a high enough sensitivity to rule out CAD in these patients without the need for further investigation.
The emergency physician is well placed, once an acute coronary syndrome or AMI have been excluded, to perform CAD risk stratification and refer appropriate patients for further investigation either directly (e.g. for CT coronary calcification in lower risk groups) or via their local chest pain clinic service (e.g. for functional testing or invasive angiography in higher risk groups).