Assessing sensitivity and specificity of the Manchester Triage System in the evaluation of acute coronary syndrome in adult patients in emergency care: a systematic review protocol

Fernanda Ayache Nishi, Flávia Oliveira de Motta Maia, Dina Almeida de Lopes Monteiro da Cruz
JBI Database of Systematic Reviews and Implementation Reports 2015, 13 (11): 64-73

REVIEW QUESTION/OBJECTIVE: The objective of this review is to assess the sensitivity and specificity of the Manchester Triage System in the evaluation of adult patients with acute coronary syndrome in emergency departments.

BACKGROUND: Acute coronary syndrome (ACS) is a group of clinical conditions that include myocardial infarction with or without elevation of the ST segment and unstable angina. The term acute myocardial infarction (AMI) can be applied when there is evidence of myocardium necrosis with a clinical sign compatible with myocardial ischaemia. Acute myocardial infarction can be identified using clinical methods including electrocardiography (ECG), elevation in myocardium necrosis biomarkers, and imaging. Acute myocardial infarction is one of the leading causes of death and disability worldwide, and may be the first manifestation of coronary artery disease.Estimating the prevalence of coronary diseases in the general population is quite a complex task. In 2010, the prevalence of coronary diseases was reported as 6.4% among the general population in the United States.One of the main manifestations of ACS is chest pain. However, even in the presence of this typical symptom, early diagnosis of ACS is a challenge for health care professionals who initially attend to these patients. Several authors have indicated the importance and difficulty of recognizing chest pain of cardiac origin, where immediate medical attention is required.Triage, or risk classification, is a clinical management tool used in emergency services to guide patient flow when the need for medical attention exceeds that available. The Manchester Triage Group was developed in 1994 in the United Kingdom. The aim was to establish a consensus among physicians and nurses in the emergency room by creating a triage pattern focused on the development of the following:Thus, the Manchester Triage System (MTS) was created. The MTS simplifies the clinical management of each patient, and consequently, the whole service, by utilizing a system that defines the clinical priority for adults and children. The assessment of clinical priority needs to be fast; therefore, it is separated from the process of medical diagnosis. Restricting the time allocated for patient classification prevents an attempt to make a medical diagnosis at the time of classification.The main goal of the MTS is to set a time limit for each patient to be attended to safely, that is, with no risk to the patient's health. One of the main principles of the system is the higher the perceived risk to the patient's health, the shorter the waiting time for medical attendance. The MTS comprises a scale of five priority levels ().(Table is included in full-text article.)The MTS is composed of 52 distinct flowcharts that "guide" the triage decision-making process. Based on the main presenting symptom of the patient seeking emergency care, the health care professional must choose one of the 52 flowcharts in order to proceed with evaluation. Classification into one of the five clinical priority levels is set for each patient using the selected flowchart.The lack of a risk classification system within an emergency room implies attendance on a first-come, first-served basis, which in many cases may jeopardize a patient's safety, as patients whose health status is more unstable or severe are not prioritized.The MTS is a tool that aims to define the degree of severity and associated safe waiting time for patients in the emergency department, establishing an order of priority for medical care. It determines the clinical priority of every patient who comes to the emergency department. It is possible to evaluate the sensitivity and specificity of the MTS by calculating the frequency of appropriately assigned clinical priority levels to patients presenting at the emergency department.A "diagnostic test" can be understood as a laboratory or imaging test: however, the concepts related to "test" also apply to clinical information from other findings, such as physical examination and patient history. The sensitivity of a test is understood as the capacity of the test to detect individuals who present with a particular condition, or the proportion of individuals with a particular condition who have been tested positive for this condition (true positive). Highly sensitive tests can be used at the beginning of the diagnostic process, when a great number of possibilities are being considered, with the intention of excluding as many options as possible. The specificity of a test is defined as the capacity of the test to identify individuals who do not have a particular medical condition, or the proportion of individuals without the condition who have a negative test (true negative). A triage system that presents a good sensitivity can minimize the occurrence of undertriage, the same way, systems with suitable specificity can avoid the occurrence of overtriage.The assessment of patients with ACS suspected using the MTS, can occur through different flow charts, since the patient does not always have typical symptoms and concerns such as chest pain as the main complaint. For this reason, in addition to the flowchart "chest pain", other flowcharts, including "shortness of breath in adults", "unwell adult", "collapsed adult", and "palpitations", enable distinguishing chest pain and other urgent conditions from non-urgent conditions, and can assist the appraiser to establish the highest priority level to treat patients with these urgent conditions.According to the algorithm from the American Heart Association, every patient who presents symptoms of chest discomfort suggestive of ischaemia must receive medical attention within 10 minutes. Therefore, in order to recognize patients in those conditions, the health care professional applying MTS must establish priority levels of "red" or "orange", thereby setting a safe waiting time for these patients.Although there are well-established criteria for the prioritization of patients with suspected ACS, several studies have reported the difficulties of evaluating patients with these conditions. Various factors can interfere with the outcome of this process, such as atypical presentation of symptoms, AMI classification, patient age, and professional skill.Primary studies have addressed the issue from different perspectives. Studies have been conducted to evaluate the ability of nurses using MTS to detect high-risk patients with chest pain, the impact of MTS on short-term mortality in AMI, and the sensitivity and specificity of MTS for patients with ACS, and to assess whether the MTS was used effectively in patients admitted to the hospital with a diagnosis of acute coronary syndrome.These studies concluded that use of the MTS by nurses is a sensitive method for identifying high risk cardiac chest pain, but further studies are required to assess whether additional training can improve the sensitivity of MTS. The MTS safeguards patients with typical AMI presentation and ST elevation during myocardial infarction, and who are under 70 years of age. The MTS has a high sensitivity in prioritization (immediate/very urgent) of patients with ACS. Additionally, most patients admitted for ACS are initially triaged as "orange" or "yellow", an indication for prompt assessment in the emergency department. This has a positive effect on time to first medical assessment, but has no effect on time to hospital admission.A systematic review addressing a similar theme was published. The review evaluated the efficacy of MTS for all groups of patients and included studies that evaluated the MTS in relation to different outcomes. This proposed review is different as it will include primary studies with a specific sub-population (patients with ACS). Another important difference lies in the fact that the published review did not include critical appraisal of the primary studies included in review. A systematic review that synthesizes the available evidence on the sensitivity of MTS to evaluate patients with an ACS medical diagnosis is necessary to guide decisions related to the use or adoption of the instrument, as well as providing data that can contribute to improvements to the system.

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