This review concluded that the main value of 64-slice or higher computed tomography angiography was to rule out significant coronary artery disease patients who were candidates for standalone diagnosis with invasive coronary angiography. This conclusion reflects the data presented, but should be interpreted cautiously as the review methodology was weak and there were some limitations in the analytical methods.

To assess the diagnostic performance of 64-slice or higher computed tomography (CT) angiography in patients with suspected coronary artery disease.

This systematic review was an up-date of a previous health technology assessment (see Other Publications of Related Interest). MEDLINE, EMBASE, The Cochrane Library and HTA databases were searched from December 2006 to March 2009 for studies in English. Search terms were reported. Conference abstracts were excluded.

Eligible studies assessed the diagnostic accuracy of 64-slice or higher CT angiography compared with the reference standard of invasive coronary angiography, in patients with suspected coronary artery disease. Studies were required to define a positive test result as 50% or greater stenosis and to report the absolute number of true positives, false positives, false negatives and true negatives, or sensitivity and specificity. Data could be presented at the patient, vessel or arterial segment level.

Studies with less than 50 participants were excluded.

The mean age of study participants ranged from 53.9 to 68.2 years and the number of male participants ranged from 53% to 85%. Where reported, the prevalence of coronary artery disease ranged from 24.8% to 85%. Studies generally excluded patients who had undergone a previous percutaneous coronary intervention or coronary artery bypass graft, patients who had a contraindication to CT angiography (such as allergy to iodinated contrast agent) and patients with atrial fibrillation, impaired renal function or inability to follow the breath hold command required to complete the test. No study excluded patients based on calcification of the coronary arteries. Most patients in included studies were given β-blockers prior to imaging in order to reduce their heart rate.

Studies were assessed for inclusion by one reviewer and assessments were not checked.

The methodological quality of included studies was assessed with the QUADAS tool and studies were also assigned a level of evidence according to the National Health and Medical Research Council of Australia diagnostic levels of evidence.

The authors did not state how many reviewers performed the quality assessment.

Data were extracted on the number of true positive, false positive, false negative and true negative test results at patient, vessel and arterial segment level, as reported. Extracted data were used to calculate sensitivity, specificity and positive and negative predictive values with 95% confidence intervals (CIs).

One review extracted data with a standard form.

Pooled estimates of sensitivity, specificity, positive predictive values, negative predictive values and overall accuracy, with 95% confidence intervals, were calculated for patient, vessel, and arterial segment level data. Studies were weighted by sample size. Summary receiver operating characteristic curves were generated with the Moses and Littenberg model.

Initial meta-analyses omitted studies that excluded indeterminate test results. The following secondary meta-analyses (in order of preference) were undertaken and included all studies that presented patient-level data: equivocal test results included and treated as test positive with disease status as determined by invasive coronary angiography correctly assigned; equivocal test results treated as false positives, where invasive coronary angiography result was unknown; equivocal test results excluded.

Twenty eight studies (3,674 patients; range 51 to 402) were included in the review. Nine studies were assessed as Level II diagnostic evidence, 15 as Level III-1 evidence and four as Level III-2 evidence. Regardless of the order of testing, all studies performed invasive coronary angiography independently of CT angiography. In all but two studies, CT angiography results were interpreted blind to the results of the reference standard. Nine recruited patients consecutively and there were two retrospective studies.

Patient level: The initial meta-analysis, which omitted studies that excluded equivocal test results, gave sensitivity estimates of 98.2% (95% CI 97.4 to 98.8%) and specificity estimates of 81.6% (95% CI 79.0 to 84.0%), 18 studies. Secondary analyses showed little difference in results.

Vessel level: The overall vessel level analyses, which omitted studies that excluded equivocal test results, showed similar diagnostic performance to that of the patient-level analysis. The sensitivity estimates were 94.9% (95% CI 93.9 to 95.8%) and specificity estimates were 89.5% (95% CI 88.8 to 90.2 %), 17 studies. Specificity was slightly higher in the left main artery 97.1% (95% CI 95.7 to 98.1%) and slightly lower in the left anterior descending artery 84.5% (95% CI 82.1 to 86.7%) compared with the other arteries.

Segment level: The overall segment level analysis gave sensitivity estimates of 91.3% (95% CI 90.2 to 92.2%) and specificity estimates of 94.0 (95% CI 93.7 to 94.2%), 17 studies.

Positive predictive values, negative predictive values and accuracy results were also reported.

The authors concluded that their review supported previous findings that the main value of 64-slice CT angiography was to rule out significant coronary artery disease. They noted that overall diagnostic accuracy varied at the individual artery level, with results being slightly worse for the left anterior descending and circumflex arteries compared with the right coronary and left main arteries.

The review addressed a clearly stated research question, which was defined by appropriate inclusion criteria. Several sources were searched for relevant studies but the exclusion of conference abstracts and non-English studies raised the possibility of publication and language biases; relevant studies may have been omitted from the review. The review process appears to have been conducted by a single reviewer throughout, which increased the likelihood of error and/or reviewer bias. The methodological quality of included studies was assessed and summarised in the text, but the full results of quality assessment were not reported, which made it difficult to judge the reliability of individual studies. The meta-analytic methods used were broadly appropriate but other methods (bivariate or hierarchical models) were now widely recommended; no assessment of between-study heterogeneity was reported.

The authors' conclusions reflected the data presented, but should be interpreted cautiously as the review methodology was weak and there were some limitations in the analytical methods.

Practice: The authors stated that it was unlikely that CT angiography will replace invasive coronary angiography in assessment for revascularisation of patients, particularly as angiography and angioplasty were often performed on the same occasion. For those patients who were candidates for standalone diagnosis with invasive coronary angiography, CT angiography may be a viable alternative. In under-serviced and under-resourced health areas, where invasive coronary angiography was not always available, CT angiography appeared to be a viable alternative.

Research: The authors did not specify any recommendations for future research.

New Zealand Ministry of Health.

Mowatt G, Cummins E, Waugh N, Walker S, Cook J, Jia X, Hillis GS, Fraser C. Systematic review of the clinical effectiveness and cost-effectiveness of 64-slice or higher computed tomography angiography as an alternative to invasive coronary angiography in the investigation of coronary artery disease. Health Technol Assess 2008, 12(17):iii-143.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.