Meta-analysis: Low-Dose CTA Equivalent to Angiography in Ruling Out CAD

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Recent efforts to reduce the radiation dose delivered by coronary computed tomographic angiography (CTA) have yielded a safer version of the diagnostic technology, one that matches the sensitivity of catheter-based angiography in ruling out coronary artery disease in symptomatic patients, according to a small meta-analysis published in the March 15, 2011, issue of Annals of Internal Medicine

Researchers led by Moritz Wyler von Ballmoos, MD, PhD, MPH, of Children’s Hospital Boston (Boston, MA), reviewed the medical literature through October 2010 to find 16 trials (n = 960) that compared the accuracy of standard angiography with low-dose CTA in patients with a clinical suspicion of CAD. Overall, 2,622 coronary arteries and 11,518 coronary arterial segments were examined. The average estimated effective radiation dose for low-dose CTA was 2.7 mSv, compared with about 12 mSv from CTA scanners prior to the introduction of prospective ECG gating and other techniques to reduce radiation dosage. 

None of the studies included in the meta-analysis were published earlier than 2008. Thirteen studies provided data at the patient level, 12 at the vessel level, and 13 at the segment level. On average, 2.4% of the coronary segments were of nondiagnostic image quality, while 1 or more segments were nondiagnostic in 9.5% of the patients.

CTA machines evaluated in the meta-analysis included:

  • Single source, 64 slice (7 studies)
  • Dual source, 64 slice (4 studies)
  • Single source, 320 slice (2 studies)
  • Dual source, 128 slice (1 study)
  • Single source, 128 slice (1 study)
  • Single source, 256 slice (1 study)

At the segment, vessel, and patient level, low-dose CTA had high sensitivity and specificity compared with standard angiography (table 1).

Table 1. Sensitivity, Specificity of CTA vs. Angiography

 

Sensitivity
(95% CI)

Specificity
(95% CI)

Segment Level

0.91
(0.86-0.95)

0.96
(0.94-0.97)

Vessel Level

0.97
(0.95-0.98)

0.93
(0.89-0.96)

Patient Level

1.00
(0.98-1.00)

0.89
(0.85-0.92)

 

At the patient level, positive and negative risk ratios were 9.2 (95% CI 6.7-12.5) and 0.0 (95% CI 0.0-0.02), respectively, and low-dose CTA showed a consistently high negative predictive value across a broad range of populations with widely varying pretest probabilities for CAD (0% to 80%).

Body-mass index and CAD prevalence were independently associated with the diagnostic performance of low-dose coronary CTA.

Only 3 studies assessed data on potential harms of low-dose CTA, but the data were not comprehensive enough to allow for a reliable comparison of the frequency and severity of acute adverse effects between the imaging modalities.

“The pooled estimates of our meta-analysis...suggest that the sensitivity of CT angiography is equivalent to that of catheter angiography at the patient level,” the researchers conclude. “The data thus support using low-dose coronary CT angiography instead of catheter angiography for triaging patients who have a low- to intermediate-pretest probability of CAD, a population for whom clinical decision making for further testing and treatment tends to be demanding.”

 

Source:

von Ballmoos MW, Haring B, Juillerat P, Alkadhi H. Meta-analysis: Diagnostic performance of low-radiation-dose coronary computed tomography angiography. Ann Intern Med. 2011;154:413-420.

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Disclosures
  • Statements regarding conflicts of interest were not available for this study.

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