STABLE ANGINA PECTORIS Diagnostic strategies The widespread application of specialist clinics for early evaluation of patients with chest pain has focused attention on the effectiveness of diagnostic testing. In a study of nearly 400 000 patients with suspected coronary artery disease, the diagnostic yield of cardiac catheterisation was only 37.6%, leading to calls for better strategies for risk stratification. 1 As pointed out in correspondence, the low yield was probably due to verification bias, itself a consequence of basing referral decisions in lowrisk populations on non-invasive tests such as exercise ECG. 2 Similar considerations prompted the NICE guideline group to recommend a more selective approach to non-invasive testing based on a careful clinical assessment of disease probability in patients presenting with stable chest pain. 3 For those, with unequivocal histories at the extremes of diagnostic probability (< 10% or> 90%) no diagnostic tests were considered necessary, while for patients with a high probability of disease (60e90%) invasive angiography without prior ischaemia testing was recommended. The NICE call for CT calcium scoring in patients with a low (10e30%) probability of disease generated greatest concern, particularly after a report that 19% of patients without coronary calcificationdwho would have been ruled out for angina in the NICE algorithmdhad obstructive (> 50% stenosis) disease. 4 However, the population referred for angiography in this study had a high pre-test probability of disease and in lower-risk populations CT calcium scoring retains a high diagnostic sensitivity. 5 NICE recommendations were driven largely by cost-effectiveness analysis but whether they will improve the diagnostic yield of cardiac catheterisation remains to be seen.

Circulating biomarkers in stable angina The clinical role of circulating biomarkers for diagnosis of obstructive coronary artery disease in patients with suspected angina has yet to be defined. In one study, blood samples for the N-terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP) and various inflammatory markers were obtained in 243 patients before myocardial perfusion imaging. Only NT-proBNP proved significantly diagnostic, a cutoff-concentration< 25ng/l predicting a normal perfusion scan with a negative predictive value> 95%. 6 Similarly, in an angiographic study of 848 men and women with clinically suspected coronary artery disease, NT-proBNP performed better than