CT coronary angiography (CTCA) is performed in a 55-year-old with atypical chest pain and intermediate pre-test probability. The calcium score (Agatston score) is 0. What does a calcium score of 0 indicate?
- A Absence of coronary artery disease — no further testing needed
- B Very low likelihood of obstructive CAD with excellent 5-year MACE-free prognosis (negative predictive value >99%) ✓
- C Soft plaques may still be present and further invasive angiography is needed
- D Coronary vasospasm rather than obstructive CAD
Correct answer: B. Very low likelihood of obstructive CAD with excellent 5-year MACE-free prognosis (negative predictive value >99%)
Explanation
An Agatston calcium score of 0 indicates absence of calcified coronary plaque and confers excellent prognosis — a 5-year major adverse cardiovascular event (MACE) rate of <1%, with a negative predictive value >99% for obstructive CAD. However, it does not exclude soft (non-calcified) plaques, which can still cause ACS; therefore in symptomatic patients with zero calcium score, CTCA with soft plaque assessment may be needed. In asymptomatic individuals for risk stratification, a score of 0 is highly reassuring and may defer statin initiation.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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