Background The NICE clinical guideline for chest pain of recent onset (NCG 95) published in March 2010 recommends diagnosing angina based on clinical assessment and likelihood of coronary artery disease (CAD). If the estimated likelihood of CAD is 61%–90%, coronary angiography should be offered. If 30%–60%, functional imaging should be offered, and if 10%–29%, CT calcium scoring should be offered. We determined the number and types of different investigations to diagnose coronary artery disease in patients referred with suspected cardiac pain before the publication of NCG 95 and compared this with the predicted investigations after the application of the guidelines.

Methods Data was collected prospectively in a bespoke database for patients referred to the Rapid Access Chest Pain Clinic, Newcastle upon Tyne, UK. Patients with chest pain of suspected cardiac origin were referred from primary care between February 2002 and March 2010. Patients with previous MI, PCI or CABG were excluded. The analysis comprised 5598 men and women with no past history of coronary disease. Likelihood of CAD was calculated by the Pryor equation using the variables age, sex, type of chest pain (typical or atypical), ECG Q waves, smoking, hyperlipidaemia, diabetes and ST/T changes on ECG. The main outcome measures were actual and predicted future frequency of exercise tests, CT coronary angiograms, functional imaging tests and invasive coronary angiograms by pretest likelihood of coronary artery disease.

Results The proportion of the study population before and after the guidelines undergoing exercise testing was 50.1% vs 0.0%; for calcium score/CT coronary angiography 0.0% vs 14.7%; for functional imaging 25.6% vs 13.4%; and for invasive coronary angiography 15.3% vs 25.8%. The proportion not requiring further testing was unchanged (30.0% vs 31.0%).

Conclusions Application of NICE CG95 will change the investigation of patients with chest pain substantially. A significant reallocation of resources will be required. Exercise testing will be replaced by anatomic or functional imaging. CT coronary angiography will play an important role and replace functional imaging in some patients. Invasive angiography will take on a more important role in the diagnosis of coronary artery disease. It will, however, empower us to reassure almost a third of referrals that they do not have angina on clinical assessment alone.