Cardiovascular disease is a class of diseases that affect the heart and the blood vessels and is the most common cause of morbidity and mortality worldwide. In many cardiovascular conditions, such as heart attack (myocardial infarction), delayed treatment may result in significant complications and death. Correct and timely diagnosis is, therefore, crucial for patients to receive prompt evidence-based treatment and to achieve the best possible outcomes. It is also important for optimal management of hospital resources and for avoiding unnecessary diagnostic and treatment procedures that may have negative impact on patients’ care. Diagnostic tests that help physicians to diagnose cardiovascular conditions and to decide on the most appropriate course of action range from patients’ history and clinical examination to electrocardiograms (ECG), blood tests and imaging techniques, some of which are expensive and involve radiation exposure and other possible adverse effects. Appropriate use of these tests requires careful consideration of their effectiveness which, among the other things, includes their diagnostic accuracy—the ability to differentiate between patients who have the target condition and those who don’t. Given the constant improvement of diagnostic technologies and the numerous primary studies evaluating their performance, diagnostic accuracy reviews are helpful as they allow comprehensive and systematic search and evaluation of all available evidence on the accuracy of specific diagnostic tests and, in some cases, improves the precision of test accuracy indices by combining the results from a number of individual studies.
1. Systematic reviews
In this project we worked with the Peninsula Heart and Stroke Network and a number of local specialists to identify relevant research topics and produce systematic reviews that could help clinicians, policy makers and patients to make better decisions about diagnostic tests and, ultimately, achieve better outcomes. At present, we are working on two systematic reviews that focus on the same condition—acute coronary syndrome (ACS)—but assess the diagnostic accuracy of two different tests:
- Coronary computed tomography angiography (CCTA)— an imaging technique that uses x-rays to create a 3D picture of the heart’s arteries in order to identify obstructions to the blood flow; and,
- Highly sensitive cardiac troponin (hs-cTn) assay—a blood test that, when positive, indicates damage to the heart muscle.
The full titles of the reviews are as follows:
- Diagnostic accuracy of Cardiac Computed Tomography Angiography for the diagnosis of Acute Coronary Syndrome in Emergency Department patients with working diagnosis of Non-ST-segment Elevation Acute Coronary Syndrome —A systematic review of the literature and meta-analysis.
- Highly sensitive cardiac troponin T assay (Roche® Diagnostics) for the diagnosis of Acute Myocardial Infarction in patients presenting to the Emergency Department with symptoms suggestive of Acute Coronary Syndrome—A systematic review of the literature and meta-analysis.
Acute coronary syndrome (ACS) covers acute myocardial infarction (AMI) (heart attack), in which part of the heart muscle is dying due to interrupted or highly reduced blood supply, and unstable angina (UA), a less severe condition, in which the insufficient blood supply causes similar symptoms but without the irreversible damage observed in AMI. Patients experiencing symptoms suggestive of ACS, such as chest pain and shortness of breath, are treated as medical emergency and need urgent diagnosis and risk stratification to guide appropriate management. Patients with AMI benefit from early invasive treatment to avoid or minimise the damage to the heart; patients with less severe condition could be managed by medications to avoid the risks involved in invasive diagnostic and treatment procedures such as catheterization and angioplasty; and patients whose chest pain is caused by medical conditions that do not require urgent medical attention could be discharged and managed as outpatients to avoid overcrowding of ED and unnecessary hospitalisations. The diagnosis and risk stratification of patients suspected of ACS is, however, challenging as the first line of diagnostic tests—patient history and clinical examination, rest ECG and blood tests—are not very accurate. To avoid inappropriate discharge many patients are admitted to hospital for clinical observation and serial testing. On the one hand, this may lead to delayed diagnosis and treatment in patients who need urgent reperfusion therapy; on the other, many patients with such symptoms do not suffer from ACS and could be safely discharged home.
The two tests evaluated in the diagnostic accuracy reviews we are currently conducting may be able to help emergency physicians to diagnose patients suspected of ACS early after presentation, thus avoiding unnecessary delays and hospitalisation. Since no clear guidelines exist for the use of these tests in the emergency setting, systematic review of the evidence on their diagnostic performance may help clinicians and policy makers make better decisions as to the application of these tests in clinical practice.
Apart from conducting systematic reviews, the CaRoTT project also aims to develop the research capacity of PenTAG by allowing a team of systematic reviewers to gain experience in conducting diagnostic accuracy reviews—a specific type of systematic reviews that differs from the familiar effectiveness reviews both in focus and methodology and requires additional knowledge and skills.
In Spring/Summer 2014, Dr Zhivko Zhelev and Harriet Hunt will be running a seminar series on diagnostic accuracy following a successful bid to the University of Exeter Researcher-led Initiative Award. The seminar series aims to:
- Increase the research capacity of Medical School researchers interested in diagnostic accuracy research
- Create a forum to discuss methodological issues
- Share knowledge and experience
- Provide an opportunity for networking, with the ambition of developing ideas for future work in this area
These seminars follow a successful series of Autumn 2013 workshops run by Dr Zhelev, Professor Chris Hyde and Harriet Hunt which gave an introduction to the diagnostic accuracy research, test accuracy reviews and the analysis and presentation of test accuracy review data.
Diagnostic accuracy of Cardiac Computed Tomography Angiography for the diagnosis of Acute Coronary Syndrome in Emergency Department patients with working diagnosis of Non-ST-segment Elevation Acute Coronary Syndrome —A systematic review of the literature and meta-analysis:
- The review protocol has been approved and registered on the PROSPERO website.We are currently conducting a second round of screening to identify the studies that will be included in the systematic review.
- We have also prepared a briefing paper, summarising our findings from reviewing all previous systematic reviews in this area, which was presented at a meeting of the Peninsula Heart and Stroke Network.
Highly sensitive cardiac troponin T assay (Roche® Diagnostics) for the diagnosis of Acute Myocardial Infarction in patients presenting to the Emergency Department with symptoms suggestive of Acute Coronary Syndrome—A systematic review of the literature and meta-analysis:
- The review protocol has been drafted and circulated among the review team for feedback.