Coronary artery disease
Analytic Approaches to Establish the Diagnostic Accuracy of Coronary Computed Tomography Angiography as a Tool for Clinical Decision Making

https://doi.org/10.1016/j.amjcard.2006.11.053Get rights and content

Although 64-slice multidetector coronary computed tomography angiography (CTA) has been reported to have excellent test characteristics for the detection of significant coronary artery disease, current analytic approaches may not appropriately reflect the process of clinical decision making. Thirty-seven patients (29 men; mean age 63 ± 11 years) who underwent coronary CTA for clinical indications followed by invasive coronary angiography within 4 weeks were studied. Computed tomography angiograms were analyzed independently for the presence of significant coronary artery stenosis (≥50% luminal narrowing) by 2 observers blinded to invasive coronary angiographic results. The diagnostic test performance of coronary CTA was determined with and without inclusion of unassessable segments. Because stenosis could not be excluded in unassessable segments, these segments were counted as positive for stenosis. Sensitivity, specificity, and positive (PPV) and negative predictive values of CTA for detecting significant stenoses on assessable segments were 85% (51 of 60, 95% confidence interval [CI] 76% to 94%), 99% (414 of 416, 95% CI 99 to 100), 96% (95% CI 51 of 53), and 98% (95% CI 414 of 423), respectively. Overall, 13% of coronary segments (70 of 546) were not assessable using CTA (heavy calcium in 48 segments). By including these segments, PPV decreased from 96% to 60% (74 of 123), whereas sensitivity improved from 85% to 89% (95% CI 74 of 83). In conclusion, the clinical utility of coronary CTA may be limited by a low PPV in patients with a high prevalence of coronary artery disease.

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Methods

We included subjects who were referred for coronary CTA and subsequently underwent invasive coronary angiography within 4 weeks of CT from January to August 2005. All patients who underwent previous coronary artery bypass grafting were excluded from the study. Clinical data, including demographics and co-morbidities, were collected using medical record review. The institutional review board approved the study.

According to our standard protocol, all patients with a heart rate >60 beats/min

Results

Overall, we included 37 patients in the study (29 men; mean age 63 ± 11 years). Patient characteristics are listed in Table 1. Of the total 576 segments, we assessed 546 matching segments for the presence of stenosis, because 30 segments after occlusion were excluded from analysis. Fifteen percent of segments (83 of 546) and 78% of patients (29 of 37) showed significant stenosis. Invasive coronary angiography detected 13 patients (35%) with single-vessel disease, 12 patients (32%) with 2-vessel

Discussion

In this study, we show that test characteristics of coronary CTA for the detection of significant stenosis in a high-risk population change considerably depending on the “treatment” of unassessable segments. Specifically, our data suggest that PPV decreases dramatically (96% to 60%) if unassessable segments are considered not able to exclude a stenosis and thus counted as positive. Conversely, assuming unassessable segments were negative for a significant stenosis, NPV decreased from 98% to 94%

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1

Dr. Shapiro, Dr. Butler, and Dr. Ferencik were supported by Grant No. 1T32 HL076136-02 from the National Institutes of Health, Bethesda, Maryland.

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