Could coronary artery calcium scores replace exercise stress testing? A DGH analysis

The National Institute for Health and Clinical Excellence (NICE) has issued guidance on the investigation of patients with recent onset of chest pain, recommending CT calcium scoring (CAC) as the preferred test in some low-risk groups. This reflects concern about the low sensitivity (high false positive rate) of exercise stress tests (EST). This represents a major shift away from traditional rapid-access EST clinics and has generated concern. We looked at 125 consecutive ungraded patients with equivocal ESTs referred for CAC, and CT coronary angiography (CTA), if required. We found that 53% of patients had a CAC = 0 and would need no further testing under the NICE protocol. We estimate this would rise up to 70–80% if only low likelihood patients were studied. Two per cent of patients with a CAC = 0 required coronary intervention.

As per NICE protocol, all patients with a CAC between 1 and 400 underwent CTA, and, of these, 25% required invasive coronary angiography (ICA) and 17% underwent coronary intervention. 

The overall strategy of CAC followed by CTA (if CAC between 1 and 400) and ICA (if CAC >400) produced a final sensitivity of 88% (higher than EST) and a negative predictive value of 98% (similar to EST). We believe the strategy is a useful way to assess recent onset chest pain but concerns about radiation dose, availability and patients with obstructive non-calcific plaque remain.

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