|A meta-analysis and systematic review of computed tomography angiography as a diagnostic triage tool for patients with chest pain presenting to the emergency department
|Samad Z, Hakeem A, Mahmood SS, Pieper K, Patel MR, Simel DL, Douglas PS
This review concluded that coronary computed tomography angiography had a high sensitivity and a low negative likelihood ratio, and could effectively rule out acute coronary syndrome for low to intermediate risk patients, with acute chest pain, in the emergency department. The review and included studies had some limitations, and the conclusions should be treated with caution.
To assess the clinical utility of computed tomography (CT) angiography in the diagnosis of patients in the emergency department with chest pain and suspected acute coronary syndrome.
PubMed, the US National Institutes of Health website, and The Cochrane Library were searched to June 2011; search terms were reported.
Prospective studies with at least one month of follow-up that used CT angiography in the emergency department for at least 30 patients with chest pain and an initial negative electrocardiogram and biomarker evaluation, were eligible for inclusion. Studies had to use the American College of Cardiology (ACC) or American Heart Association (AHA) definitions for acute coronary syndrome and major adverse cardiac events. They had to use acute coronary syndrome as the clinical outcome or end point and present sufficient data to construct 2x2 tables of test performance. Studies published as abstracts only were excluded.
In the included studies, the mean age of participants was 52 years, 51% were male, 12% had diabetes, 42% had hypertension, 35% were smokers, and 29% had hyperlipidaemia. Most studies excluded patients with a history of coronary heart disease. Most studies used 64-slice CT scanners and conducted CT angiography in the emergency department, during evaluation; others conducted CT angiography in an observation unit while awaiting admission, or immediately upon admission. The definition for an abnormal CT angiography varied across studies; the minimal requirement was 50% luminal obstruction. Between 60 and 100mL of contrast was used in most studies. The total radiation dose administered was poorly reported.
The authors did not state how many reviewers selected studies for the review.
Assessment of study quality
Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool; the results were reported for consecutive enrolment, blinding, and interpretable results. The authors did not state how many reviewers assessed quality.
Data were extracted by two independent reviewers to construct 2x2 tables of test performance. Sensitivity, specificity, positive and negative likelihood ratios, positive and negative predictive values, and the diagnostic odds ratio, with 95% confidence intervals, were calculated. Disagreements were resolved by a third reviewer or by consensus.
Methods of synthesis
Summary estimates for sensitivity and specificity were calculated, using a random-effects bivariate model, from which summary positive and negative likelihood ratios were calculated. Acute coronary syndrome (acute myocardial infarction or unstable angina) was the gold standard for the primary analysis. Spearman correlation coefficients were used to investigate any threshold effect. A weighted regression of the diagnostic odds ratio was conducted. Heterogeneity was assessed using Ι². Publication bias was assessed using funnel plots and the Egger regression test.
Results of the review
Nine studies met the inclusion criteria, with 1,349 patients (range 34 to 568); one was a randomised controlled trial, from which a cohort was derived, and eight were observational cohort studies. Seven studies recruited consecutively, two blinded the physicians to the results of the CT angiography, and six reported the percentage of scans that could not be interpreted (range 1% to 17%).
CT angiography had a sensitivity for detecting acute coronary syndrome of 100% in five studies; the summary estimate was 95% (95% CI 88 to 100; Ι²=0). The summary estimate of specificity was 87% (95% CI 83 to 92; Ι²=74%), the positive likelihood ratio was 7.4 (95% CI 4.8 to 10; Ι²=71%), and the negative likelihood ratio was 0.06 (95% CI 0 to 0.14; Ι²=0). No inverse correlation between sensitivity and specificity, and no threshold effect was detected. A potential for publication bias was observed.
Coronary CT angiography had a high sensitivity and a low negative likelihood ratio, and could effectively rule out acute coronary syndrome for low to intermediate risk patients, with acute chest pain, in the emergency department.
The review addressed a clear question. The inclusion criteria for study design were unclear; it was stated in the results that the main reason for exclusion was a design other than clinical trial, but a cohort from one randomised controlled trial was included and the other studies were observational cohort studies. Relevant sources were searched, but it was unclear whether language restrictions were applied and there was no specific attempt to identify unpublished studies. Data extraction was conducted in duplicate, but it was unclear whether similar methods to reduce error and bias were used for study selection and quality assessment.
Study quality was assessed using relevant criteria, but not all potential sources of bias were investigated. Robust methods of analysis were used to derive the summary estimates. Most of the studies were small, and the prevalence of acute coronary syndrome seems to have varied considerably across studies; the impact of this was not considered.
Given the limitations of the review and the uncertainty in the quality of the included studies, the conclusions should be treated with caution.
Implications of the review for practice and research
Practice: The authors stated that a positive CT angiography significantly increased the probability of acute coronary syndrome and could be helpful in making a timely triage decision. They stated that their results supported and strengthened the 2010 appropriateness criteria for cardiac CT and, for patients with scans that could not be interpreted, the recommended evaluation algorithms were valid.
Research: The authors stated that more studies were required to confirm the low negative likelihood ratio. Future studies should consider whether to include or exclude patients with known coronary disease or a significant likelihood of acute coronary syndrome. Sample size estimates should be based on the prevalence of disease in the setting. There was a need for randomised studies to compare CT angiography with usual practice and evaluate real-time test performance. There was a need to investigate initial non-enhanced electrocardiogram-gated scans for calcium scoring, cost-effectiveness, and clinical care patterns. Acute coronary syndrome in the absence of a coronary stenosis could be addressed in future trials, and the diagnostic accuracy and risk benefit ratio of performing CT scans could be investigated in patient subgroups.
Samad Z, Hakeem A, Mahmood SS, Pieper K, Patel MR, Simel DL, Douglas PS. A meta-analysis and systematic review of computed tomography angiography as a diagnostic triage tool for patients with chest pain presenting to the emergency department. Journal of Nuclear Cardiology 2012; 19(2): 364-376
Subject indexing assigned by NLM
Acute Coronary Syndrome /epidemiology /radiography; Acute Disease; Chest Pain /epidemiology /radiography; Coronary Angiography /statistics & numerical data; Emergency Medical Services /statistics & numerical data; Humans; Prevalence; Reproducibility of Results; Risk Assessment /methods; Risk Factors; Sensitivity and Specificity; Tomography, X-Ray Computed /statistics & numerical data; Triage /statistics & numerical data
Date bibliographic record published
Date abstract record published
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.