Diagnostic Accuracy of D-Dimer for Acute Aortic Syndromes: Systematic Review and Meta-Analysis.

STUDY OBJECTIVE: Acute aortic syndrome is a life-threatening emergency condition. Previous systematic reviews of D-dimer diagnostic accuracy for acute aortic syndrome have been contradictory and based on limited data, but recently published studies offer potential for a more definitive overview. We aimed to perform a systematic review and meta-analysis to determine the diagnostic accuracy of D-dimer for diagnosing acute aortic syndrome. METHODS: We searched MEDLINE, EMBASE, and the Cochrane Library from inception to February 2024. Additionally, the reference lists of included studies and other systematic reviews were thoroughly searched. All diagnostic cohort studies (prospective or retrospective) that assessed the use of D-dimer for diagnosing acute aortic syndrome compared with a reference standard test (eg, computed tomographic angiography (CTA), ECG-gated CTA, echocardiography, magnetic resonance angiography, operation, or autopsy) were included. Two independent reviewers completed study selection, data extractions and quality assessment using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Data were synthesized using a bivariate meta-analysis model. RESULTS: Of 2017 potentially relevant citations, 25 cohort studies met the inclusion criteria, and 18 reporting the 500 ng/mL threshold were included in the primary meta-analysis. Risk of bias domains were mostly unclear due to limited study reporting. The summary sensitivity was 96.5% (95% credible interval [CrI] 94.8% to 98%) and summary specificity was 56.2% (95% CrI, 48.3% to 63.9%). Study specificity varied markedly from 33% to 86%, indicating substantial heterogeneity. Sensitivity analysis including the 7 studies reporting other thresholds showed summary sensitivity of 95.7% (95% CrI, 93.2% to 97.5%) and summary specificity of 57.5% (95% CrI, 50.1% to 64.6%). CONCLUSION: D-dimer concentration has high sensitivity (96.5%) and moderate specificity (56.2%) for acute aortic syndrome, with some uncertainty around estimates due to risk of bias and heterogeneity. Previous meta-analysis reporting higher specificity may be explained by inclusion of case-control studies that may overestimate accuracy.

Diagnosis of Acute Aortic Syndrome in the Emergency Department (DAShED) study: an observational cohort study of people attending the emergency department with symptoms consistent with acute aortic syndrome.

BACKGROUND: The diagnosis of acute aortic syndrome (AAS) is commonly delayed or missed in the ED. We describe characteristics of ED attendances with symptoms potentially associated with AAS, diagnostic performance of clinical decision tools (CDTs) and physicians and yield of CT aorta angiogram (CTA). METHODS: This was a multicentre observational cohort study of adults attending 27 UK EDs between 26 September 2022 and 30 November 2022, with potential AAS symptoms: chest, back or abdominal pain, syncope or symptoms related to malperfusion. Patients were preferably identified prospectively, but retrospective recruitment was also permitted. Anonymised, routinely collected patient data including components of CDTs, was abstracted. Clinicians treating prospectively identified patients were asked to record their perceived likelihood of AAS, prior to any confirmatory testing. Reference standard was radiological or operative confirmation of AAS. 30-day electronic patient record follow-up evaluated whether a subsequent diagnosis of AAS had been made and mortality. RESULTS: 5548 patients presented, with a median age of 55 years (IQR 37-72; n=5539). 14 (0.3%; n=5353) had confirmed AAS. 10/1046 (1.0%) patients in whom the ED clinician thought AAS was possible had AAS. 5/147 (3.4%) patients in whom AAS was considered the most likely diagnosis had AAS. 2/3319 (0.06%) patients in whom AAS was considered not possible did have AAS. 540 (10%; n=5446) patients underwent CT, of which 407 were CTA (7%). 30-day follow-up did not reveal any missed AAS diagnoses. AUROC (area under the receiver operating characteristic) curve for ED clinician AAS likelihood rating was 0.958 (95% CI 0.933 to 0.983, n=4006) and for individual CDTs were: Aortic Dissection Detection Risk Score (ADD-RS) 0.674 (95% CI 0.508 to 0.839, n=4989), AORTAs 0.689 (95% CI 0.527 to 0.852, n=5132), Canadian 0.818 (95% CI 0.686 to 0.951, n=5180) and Sheffield 0.628 (95% CI 0.467 to 0.788, n=5092). CONCLUSION: Only 0.3% of patients presenting with potential AAS symptoms had AAS but 7% underwent CTA. CDTs incorporating clinician gestalt appear to be most promising, but further prospective work is needed, including evaluation of the role of D-dimer. TRIAL REGISTRATION NUMBER: NCT05582967; NCT05582967.

Clinical decision aids and computed tomography coronary angiography in patients with suspected acute coronary syndrome.

BACKGROUND: The HEART score, the T-MACS model and the GRACE score support early decision-making for acute chest pain, which could be complemented by CT coronary angiography (CTCA). However, their performance has not been directly compared. METHODS: In this secondary analysis of a multicentre randomised controlled trial of early CTCA in intermediate-risk patients with suspected acute coronary syndrome, C-statistics and performance metrics (using the predefined cut-offs) of clinical decision aids and CTCA, alone and then in combination, for the index hospital diagnosis of acute coronary syndrome and for 30-day coronary revascularisation were assessed in those who underwent CTCA and had complete data. RESULTS: Among 699 patients, 358 (51%) had an index hospital diagnosis of acute coronary syndrome, for which the C-statistic was higher for CTCA (0.80), followed by the T-MACS model (0.78), the HEART score (0.74) and the GRACE score (0.60). The negative predictive value was higher for the absence of coronary artery disease on CTCA (0.90) or a T-MACS estimate of <0.05 (0.83) than a HEART score of <4 (0.81) and a GRACE score of <109 (0.55). For 30-day coronary revascularisation, CTCA had the greatest C-statistic (0.80) with a negative predictive value of 0.96 and 0.92 in the absence of coronary artery disease and obstructive coronary artery disease, respectively. The combination of the T-MACS estimates and the CTCA findings was most discriminative for the index hospital diagnosis of acute coronary syndrome (C-statistic, 0.88) and predictive of 30-day coronary revascularisation (C-statistic, 0.85). No patients with a T-MACS estimate of <0.05 and normal coronary arteries had acute coronary syndrome during index hospitalisation or underwent coronary revascularisation within 30 days. CONCLUSIONS: In intermediate-risk patients with suspected acute coronary syndrome, the T-MACS model combined with CTCA improved discrimination of the index hospital diagnosis of acute coronary syndrome and prediction of 30-day coronary revascularisation. TRIAL REGISTRATION NUMBER: NCT02284191.

Early computed tomography coronary angiography and preventative treatment in patients with suspected acute coronary syndrome: A secondary analysis of the RAPID-CTCA trial.

BACKGROUND: Computed tomography coronary angiography (CTCA) offers detailed assessment of the presence of coronary atherosclerosis and helps guide patient management. We investigated influences of early CTCA on the subsequent use of preventative treatment in patients with suspected acute coronary syndrome. METHODS: In this secondary analysis of a multicenter randomized controlled trial of early CTCA in intermediate-risk patients with suspected acute coronary syndrome, prescription of aspirin, P2Y12 receptor antagonist, statin, renin-angiotensin system blocker, and beta-blocker therapies from randomization to discharge were compared within then between those randomized to early CTCA or to standard of care only. Effects of CTCA findings on adjustment of these therapies were further examined. RESULTS: In 1,743 patients (874 randomized to early CTCA and 869 to standard of care only), prescription of P2Y12 receptor antagonist, dual antiplatelet, and statin therapies increased more in the early CTCA group (between-group difference: 4.6% [95% confidence interval, 0.3-8.9], 4.5% [95% confidence interval, 0.2-8.7], and 4.3% [95% confidence interval, 0.2-8.5], respectively), whereas prescription of other preventative therapies increased by similar extent in both study groups. Among patients randomized to early CTCA, there were additional increments of preventative treatment in those with obstructive coronary artery disease and higher rates of reductions in antiplatelet and beta-blocker therapies in those with normal coronary arteries. CONCLUSIONS: Prescription patterns of preventative treatment varied during index hospitalization in patients with suspected acute coronary syndrome. Early CTCA facilitated targeted individualization of these therapies based on the extent of coronary artery disease.

Using clinical risk models to predict outcomes: what are we predicting and why?

Clinical risk prediction models can support decision making in emergency medicine, but directing intervention towards high-risk patients may involve a flawed assumption. This concepts paper examines prognostic clinical risk prediction and specifically describes the potential impact of treatment effects in model development studies. Treatment effects may lead to models failing to achieve the aim of identifying the patients most likely to benefit from intervention, and may instead identify patients who are unlikely to benefit from intervention. The paper provides practical advice to help clinicians who wish to use clinical prediction scores to assist clinical judgement rather than dictate clinical decision making.

External validation of triage tools for adults with suspected COVID-19 in a middle-income setting: an observational cohort study.

BACKGROUND: Tools proposed to triage ED acuity in suspected COVID-19 were derived and validated in higher income settings during early waves of the pandemic. We estimated the accuracy of seven risk-stratification tools recommended to predict severe illness in the Western Cape, South Africa. METHODS: An observational cohort study using routinely collected data from EDs across the Western Cape, from 27 August 2020 to 11 March 2022, was conducted to assess the performance of the PRIEST (Pandemic Respiratory Infection Emergency System Triage) tool, NEWS2 (National Early Warning Score, version 2), TEWS (Triage Early Warning Score), the WHO algorithm, CRB-65, Quick COVID-19 Severity Index and PMEWS (Pandemic Medical Early Warning Score) in suspected COVID-19. The primary outcome was intubation or non-invasive ventilation, death or intensive care unit admission at 30 days. RESULTS: Of the 446 084 patients, 15 397 (3.45%, 95% CI 34% to 35.1%) experienced the primary outcome. Clinical decision-making for inpatient admission achieved a sensitivity of 0.77 (95% CI 0.76 to 0.78), specificity of 0.88 (95% CI 0.87 to 0.88) and the negative predictive value (NPV) of 0.99 (95% CI 0.99 to 0.99). NEWS2, PMEWS and PRIEST scores achieved good estimated discrimination (C-statistic 0.79 to 0.82) and identified patients at risk of adverse outcomes at recommended cut-offs with moderate sensitivity (>0.8) and specificity ranging from 0.41 to 0.64. Use of the tools at recommended thresholds would have more than doubled admissions, with only a 0.01% reduction in false negative triage. CONCLUSION: No risk score outperformed existing clinical decision-making in determining the need for inpatient admission based on prediction of the primary outcome in this setting. Use of the PRIEST score at a threshold of one point higher than the previously recommended best approximated existing clinical accuracy.

Prehospital early warning scores for adults with suspected sepsis: retrospective diagnostic cohort study.

BACKGROUND: Ambulance services need to identify and prioritise patients with sepsis for early hospital assessment. We aimed to determine the accuracy of early warning scores alongside paramedic diagnostic impression to identify sepsis that required urgent treatment. METHODS: We undertook a retrospective diagnostic cohort study involving adult emergency medical cases transported to Sheffield Teaching Hospitals ED by Yorkshire Ambulance Service in 2019. We used routine ambulance service data to calculate 21 early warning scores and categorise paramedic diagnostic impressions as sepsis, infection, non-specific presentation or other presentation. We linked cases to hospital records and identified those meeting the sepsis-3 definition who received urgent hospital treatment for sepsis (reference standard). Analysis determined the accuracy of strategies that combined early warning scores at varying thresholds for positivity with paramedic diagnostic impression. RESULTS: We linked 12 870/24 955 (51.6%) cases and identified 348/12 870 (2.7%) with a positive reference standard. None of the strategies provided sensitivity greater than 0.80 with positive predictive value greater than 0.15. The area under the receiver operating characteristic curve for the National Early Warning Score, version 2 (NEWS2) applied to patients with a diagnostic impression of sepsis or infection was 0.756 (95% CI 0.729, 0.783). No other early warning score provided clearly superior accuracy to NEWS2. Paramedic impression of sepsis or infection had sensitivity of 0.572 (0.519, 0.623) and positive predictive value of 0.156 (0.137, 0.176). NEWS2 thresholds of >4, >6 and >8 applied to patients with a diagnostic impression of sepsis or infection, respectively, provided sensitivities and positive predictive values of 0.522 (0.469, 0.574) and 0.216 (0.189, 0.245), 0.447 (0.395, 0.499) and 0.274 (0.239, 0.313), and 0.314 (0.268, 0.365) and 0.333 (0.284, 0.386). CONCLUSION: No strategy is ideal but using NEWS2 alongside paramedic diagnostic impression of infection or sepsis could identify one-third to half of sepsis cases without prioritising unmanageable numbers. No other score provided clearly superior accuracy to NEWS2. TRIAL REGISTRATION NUMBER: researchregistry5268, https://www.researchregistry.com/browse-the-registry%23home/registrationdetails/5de7bbd97ca5b50015041c33/.

Does Hospital Admission/Observation for Chest Pain Improve Patient Outcomes after Emergency Department Evaluation for Suspected Acute Coronary Syndrome?

BACKGROUND: Chest pain is the top reason for hospitalization/observation in the USA, but it is unclear if this strategy improves patient outcomes. OBJECTIVE: The objective of this study was to compare 30-day outcomes for patients admitted versus discharged after a negative emergency department (ED) evaluation for suspected acute coronary syndrome. DESIGN: A retrospective, multi-site, cohort study of adult encounters with chest pain presenting to one of 13 Kaiser Permanente Southern California EDs between January 1, 2015, and December 1, 2017. Instrumental variable analysis was used to mitigate potential confounding by unobserved factors. PATIENTS: All adult patients presenting to an ED with chest pain, in whom an acute myocardial infarction was not diagnosed in the ED, were included. MAIN MEASURES: The primary outcome was 30-day acute myocardial infarction or all-cause mortality, and secondary outcomes included 30-day revascularization and major adverse cardiac events. KEY RESULTS: In total, 77,652 patient encounters were included in the study (n=11,026 admitted, 14.2%). Three hundred twenty-two (0.4%) had an acute myocardial infarction (n=193, 0.2%) or death (n=137, 0.2%) within 30 days of ED visit (1.5% hospitalized versus 0.2% discharged). Very few (0.3%) patients underwent coronary revascularization within 30 days (0.7% hospitalized versus 0.2% discharged). Instrumental variable analysis found no adjusted differences in 30-day patient outcomes between the hospitalized cohort and those discharged (risk reduction 0.002, 95% CI -0.002 to 0.007). Similarly, there were no differences in coronary revascularization (risk reduction 0.003, 95% CI -0.002 to 0.007). CONCLUSION: Among ED patients with chest pain not diagnosed with an acute myocardial infarction, risk of major adverse cardiac events is quite low, and there does not appear to be any benefit in 30-day outcomes for those admitted or observed in the hospital compared to those discharged with outpatient follow-up.

Composite Outcomes in Clinical Prediction Modeling: Are We Trying to Predict Apples and Oranges?

Composite outcomes are widely used in clinical research. Existing literature has considered the pros and cons of composite outcomes in clinical trials, but their extensive use in clinical prediction has received much less attention. Clinical prediction assists decision-making by directing patients with higher risks of adverse outcomes toward interventions that provide the greatest benefits to those at the greatest risk. In this article, we summarize our existing understanding of the advantages and disadvantages of composite outcomes, consider how these relate to clinical prediction, and highlight the problem of key predictors having markedly different associations with individual components of the composite outcome. We suggest that a "composite outcome fallacy" may occur when a clinical prediction model is based on strong associations between key predictors and one component of a composite outcome (such as mortality) and used to direct patients toward intervention when these predictors actually have an inverse association with a more relevant component of the composite outcome (such as the use of a lifesaving intervention). We propose that clinical prediction scores using composite outcomes should report their accuracy for key components of the composite outcome and examine for inconsistencies among predictor variables.

Research priorities for prehospital care of older patients with injuries: scoping review.

BACKGROUND AND OBJECTIVE: There is increasing recognition of the importance of prehospital trauma care for older patients, but little systematic research to guide practice. We aimed to review the published evidence on prehospital trauma care for older patients, determine the scope of existing research and identify research gaps in the literature. METHODS: We undertook a systematic scoping review guided by the Arksey and O'Malley framework and reported in line with the PRISMA-ScR checklist. A systematic search was conducted of Scopus, CINAHL, MEDLINE, PubMed and Cochrane library databases to identify articles published between 2001 and 2021. Study selection criteria were applied independently by two reviewers. Data were extracted, charted and summarised from eligible articles. A data-charting form was then developed to facilitate thematic analysis. Narrative synthesis then involved identifying major themes and subthemes from the data. RESULTS: We identified and reviewed 65 studies, and included 25. We identified five categories: 'field triage', 'ageing impacts', 'decision-making', 'paramedic' awareness' and 'paramedic's behaviour'. Undertriage and overtriage (sensitivity and specificity) were commonly cited as poorly investigated field-triage subthemes. Ageing-related physiologic changes, comorbidities and polypharmacy were the most widely researched. Inaccurate decision-making and poor early identification of major injuries were identified as potentially influencing patient outcomes. CONCLUSION: This is the first study reviewing the published evidence on prehospital trauma care for older patients and identifying research priorities for future research. Field-triage tools, paramedics' knowledge about injuries in the older population, and understanding of paramedics' negative behaviours towards older patients were identified as key research priorities.

Comparison of qSOFA and Hospital Early Warning Scores for prognosis in suspected sepsis in emergency department patients: a systematic review.

BACKGROUND: Sepsis is a major cause of morbidity and mortality and many tools exist to facilitate early recognition. This review compares two tools: the quick Sequential Organ Failure Assessment (qSOFA) and Early Warning Scores (National/Modified Early Warning Scores (NEWS/MEWS)) for predicting intensive care unit (ICU) admission and mortality when applied in the emergency department. METHODS: A literature search was conducted using Medline, CINAHL, Embase and Cochrane Library, handsearching of references and a grey literature search with no language or date restrictions. Two authors selected studies and quality assessment completed using QUADAS-2. Area under the receiver operating characteristic curve (AUROC), sensitivities and specificities were compared. RESULTS: 13 studies were included, totalling 403 865 patients. All reported mortality and six reported ICU admission.The ranges for AUROC estimates varied from little better than chance to good prediction of mortality (NEWS: 0.59-0.88; qSOFA: 0.57-0.79; MEWS 0.56-0.75), however, individual papers generally reported higher AUROC values for NEWS than qSOFA. NEWS values demonstrated a tendency towards better sensitivity for ICU admission (NEWS ≥5, 46%-91%; qSOFA ≥2, 12%-53%) and mortality (NEWS ≥5, 51%-97%; qSOFA ≥2, 14%-71%) but lower specificity (ICU: NEWS ≥5, 25%-91%; qSOFA ≥2, 67%-99%; mortality: NEWS ≥5, 22%-91%; qSOFA ≥2, 58%-99%). CONCLUSION: The wide range of AUROC estimates and high heterogeneity limit our conclusions. Allowing for this, the NEWS AUROC was consistently higher than qSOFA within individual papers. Both scores allow threshold setting, determined by the preferred compromise between sensitivity and specificity. At established thresholds NEWS tended to higher sensitivity while qSOFA tended to a higher specificity. PROSPERO REGISTRATION NUMBER: CRD42019131414.

Retrospective single-centre descriptive study of the characteristics, management and outcomes of adult patients with suspected sepsis in the emergency department.

BACKGROUND: Guidelines for adults presenting to the emergency department (ED) with suspected sepsis recommend protocols and bundles that promote rapid and potentially intensive treatment, but give little consideration of how patient characteristics, such as age, functional status and comorbidities, might influence management. This study aimed to describe the characteristics, management and outcomes of adults attending the ED with suspected sepsis, and specifically describe the prevalence of comorbidities, functional impairment and escalations of care. METHODS: We undertook a single-centre retrospective observational study involving medical record review of a random sample of adults admitted to an ED between February 2018 and January 2019 with suspected sepsis. Descriptive statistics were used with 95% confidence intervals (CIs) for key proportions. RESULTS: We included 509 patients (median age 74 years), of whom 49.3% met the Sepsis-3 criteria. Less than half of the patients were living at home independently (42.5%) or could walk independently (41.5%), 19.3% were care home residents and 89.2% of patients had one or more comorbidity. 22% had a pre-existing do not attempt resuscitation order. 6.5% were referred to intensive care, and 34.3% of the 13.2% who died in-hospital had an escalation plan explicitly documented. CONCLUSION: Adults with suspected sepsis have substantial functional limitations, comorbidities and treatment directives that should be considered in guidelines, especially recommendations for escalation of care.

Prognostic accuracy of triage tools for adults with suspected COVID-19 in a prehospital setting: an observational cohort study.

BACKGROUND: Tools proposed to triage patient acuity in COVID-19 infection have only been validated in hospital populations. We estimated the accuracy of five risk-stratification tools recommended to predict severe illness and compared accuracy to existing clinical decision making in a prehospital setting. METHODS: An observational cohort study using linked ambulance service data for patients attended by Emergency Medical Service (EMS) crews in the Yorkshire and Humber region of England between 26 March 2020 and 25 June 2020 was conducted to assess performance of the Pandemic Respiratory Infection Emergency System Triage (PRIEST) tool, National Early Warning Score (NEWS2), WHO algorithm, CRB-65 and Pandemic Medical Early Warning Score (PMEWS) in patients with suspected COVID-19 infection. The primary outcome was death or need for organ support. RESULTS: Of the 7549 patients in our cohort, 17.6% (95% CI 16.8% to 18.5%) experienced the primary outcome. The NEWS2 (National Early Warning Score, version 2), PMEWS, PRIEST tool and WHO algorithm identified patients at risk of adverse outcomes with a high sensitivity (>0.95) and specificity ranging from 0.3 (NEWS2) to 0.41 (PRIEST tool). The high sensitivity of NEWS2 and PMEWS was achieved by using lower thresholds than previously recommended. On index assessment, 65% of patients were transported to hospital and EMS decision to transfer patients achieved a sensitivity of 0.84 (95% CI 0.83 to 0.85) and specificity of 0.39 (95% CI 0.39 to 0.40). CONCLUSION: Use of NEWS2, PMEWS, PRIEST tool and WHO algorithm could improve sensitivity of EMS triage of patients with suspected COVID-19 infection. Use of the PRIEST tool would improve sensitivity of triage without increasing the number of patients conveyed to hospital.

An economic evaluation of triage tools for patients with suspected severe injuries in England.

BACKGROUND: Many health care systems triage injured patients to major trauma centres (MTCs) or local hospitals by using triage tools and paramedic judgement. Triage tools are typically assessed by whether patients with an Injury Severity Score (ISS) ≥ 16 go to an MTC and whether patients with an ISS < 16 are sent to their local hospital. There is a trade-off between sensitivity and specificity of triage tools, with the optimal balance being unknown. We conducted an economic evaluation of major trauma triage tools to identify which tool would be considered cost-effective by UK decision makers. METHODS: A patient-level, probabilistic, mathematical model of a UK major trauma system was developed. Patients with an ISS ≥ 16 who were only treated at local hospitals had worse outcomes compared to being treated in an MTC. Nine empirically derived triage tools, from a previous study, were examined so we assessed triage tools with realistic trade-offs between triage tool sensitivity and specificity. Lifetime costs, lifetime quality adjusted life years (QALYs), and incremental cost-effectiveness ratios (ICERs) were calculated for each tool and compared to maximum acceptable ICERs (MAICERs) in England. RESULTS: Four tools had ICERs within the normal range of MAICERs used by English decision makers (£20,000 to £30,000 per QALY gained). A low sensitivity (28.4%) and high specificity (88.6%) would be cost-effective at the lower end of this range while higher sensitivity (87.5%) and lower specificity (62.8%) was cost-effective towards the upper end of this range. These results were sensitive to the cost of MTC admissions and whether MTCs had a benefit for patients with an ISS between 9 and 15. CONCLUSIONS: The cost-effective triage tool depends on the English decision maker's MAICER for this health problem. In the usual range of MAICERs, cost-effective prehospital trauma triage involves clinically suboptimal sensitivity, with a proportion of seriously injured patients (at least 10%) being initially transported to local hospitals. High sensitivity trauma triage requires development of more accurate decision rules; research to establish if patients with an ISS between 9 and 15 benefit from MTCs; or, inefficient use of health care resources to manage patients with less serious injuries at MTCs.

Controlled observational study and economic evaluation of the effect of city-centre night-time alcohol intoxication management services on the emergency care system compared with usual care.

BACKGROUND: Alcohol intoxication management services (AIMS) provide an alternative care pathway for alcohol-intoxicated adults otherwise requiring emergency department (ED) services and at times of high incidence. We estimate the effectiveness and cost-effectiveness of AIMS on ED attendance rates with ED and ambulance service performance indicators as secondary outcomes. METHODS: A controlled longitudinal retrospective observational study in English and Welsh towns, six with AIMS and six without. Control and intervention cities were matched by sociodemographic characteristics. The primary outcome was ED attendance rate per night, secondary analyses explored hospital admission rates and ambulance response times. Interrupted time series analyses compared control and matched intervention sites pre-AIMS and post-AIMS. Cost-effectiveness analyses compared the component costs of AIMS to usual care before with results presented from the National Health Service and social care prospective. The number of diversions away from ED required for a service to be cost neutral was determined. RESULTS: Analyses found considerable variation across sites, only one service was associated with a significant reduction in ED attendances (-4.89, p<0.01). The services offered by AIMS varied. On average AIMS had 7.57 (mean minimum=1.33, SD=1.37 to mean maximum=24.66, SD=12.58) in attendance per session, below the 11.02 diversions away from ED at which services would be expected to be cost neutral. CONCLUSIONS: AIMSs have variable effects on the emergency care system, reflecting variable structures and processes, but may be associated with modest reductions in the burden on ED and ambulance services. The more expensive model, supported by the ED, was the only configuration likely to divert patients away from ED. AIMS should be regarded as fledgling services that require further work to realise benefit. TRIAL REGISTRATION NUMBER: ISRCTN63096364.

Diagnostic accuracy of the magnetocardiograph for patients with suspected acute coronary syndrome.

BACKGROUND: We aimed to estimate the diagnostic accuracy of the VitalScan magnetocardiograph (MCG) for suspected acute coronary syndrome (ACS). METHODS: We undertook a prospective cohort study evaluating the diagnostic accuracy of the MCG in adults with suspected ACS. The reference standard of ACS was determined by an independent adjudication committee based on 30-day investigations and events. The cohort was split into a training sample, to derive the MCG algorithm and an algorithm combining MCG with a modified Manchester Acute Coronary Syndrome (MACS) clinical probability score, and a validation sample, to estimate diagnostic accuracy. RESULTS: We recruited 756 participants and analysed data from 680 (293 training, 387 validation), of whom 96 (14%) had ACS. In the training sample, the respective area under the receiver operating characteristic (AUROC) curves were the following: MCG 0.66 (95% CI 0.58 to 0.74), MACS 0.64 (95% CI 0.54 to 0.73) and MCG+MACS 0.70 (95% CI 0.63 to 0.77). MCG specificity was 0.16 (95% CI 0.12 to 0.21) at the threshold achieving acceptable sensitivity for rule-out (>0.98). In the validation sample (n=387), the respective AUROCs were the following: MCG 0.56 (95% CI 0.48 to 0.64), MACS 0.69 (95% CI 0.61 to 0.77) and MCG+MACS 0.64 (95% CI 0.56 to 0.72). MCG sensitivity was 0.89 (95% CI 0.77 to 0.95) and specificity 0.15 (95% CI 0.12 to 0.20) at the rule-out threshold. MCG+MACS sensitivity was 0.85 (95% CI 0.73 to 0.92) and specificity 0.30 (95% CI 0.25 to 0.35). CONCLUSION: The VitalScan MCG is currently unable to accurately rule out ACS and is not yet ready for use in clinical practice. Further developmental research is required.

Prognostic accuracy of emergency department triage tools for adults with suspected COVID-19: the PRIEST observational cohort study.

BACKGROUND: The WHO and National Institute for Health and Care Excellence recommend various triage tools to assist decision-making for patients with suspected COVID-19. We aimed to compare the accuracy of triage tools for predicting severe illness in adults presenting to the ED with suspected COVID-19. METHODS: We undertook a mixed prospective and retrospective observational cohort study in 70 EDs across the UK. We collected data from people attending with suspected COVID-19 and used presenting data to determine the results of assessment with the WHO algorithm, National Early Warning Score version 2 (NEWS2), CURB-65, CRB-65, Pandemic Modified Early Warning Score (PMEWS) and the swine flu adult hospital pathway (SFAHP). We used 30-day outcome data (death or receipt of respiratory, cardiovascular or renal support) to determine prognostic accuracy for adverse outcome. RESULTS: We analysed data from 20 891 adults, of whom 4611 (22.1%) died or received organ support (primary outcome), with 2058 (9.9%) receiving organ support and 2553 (12.2%) dying without organ support (secondary outcomes). C-statistics for the primary outcome were: CURB-65 0.75; CRB-65 0.70; PMEWS 0.77; NEWS2 (score) 0.77; NEWS2 (rule) 0.69; SFAHP (6-point rule) 0.70; SFAHP (7-point rule) 0.68; WHO algorithm 0.61. All triage tools showed worse prediction for receipt of organ support and better prediction for death without organ support. At the recommended threshold, PMEWS and the WHO criteria showed good sensitivity (0.97 and 0.95, respectively) at the expense of specificity (0.30 and 0.27, respectively). The NEWS2 score showed similar sensitivity (0.96) and specificity (0.28) when a lower threshold than recommended was used. CONCLUSION: CURB-65, PMEWS and the NEWS2 score provide good but not excellent prediction for adverse outcome in suspected COVID-19, and predicted death without organ support better than receipt of organ support. PMEWS, the WHO criteria and NEWS2 (using a lower threshold than usually recommended) provide good sensitivity at the expense of specificity. TRIAL REGISTRATION NUMBER: ISRCTN56149622.

Post-exertion oxygen saturation as a prognostic factor for adverse outcome in patients attending the emergency department with suspected COVID-19: a substudy of the PRIEST observational cohort study.

BACKGROUND: Measurement of post-exertion oxygen saturation has been proposed to assess illness severity in suspected COVID-19 infection. We aimed to determine the accuracy of post-exertional oxygen saturation for predicting adverse outcome in suspected COVID-19. METHODS: We undertook a substudy of an observational cohort study across 70 emergency departments during the first wave of the COVID-19 pandemic in the UK. We collected data prospectively, using a standardised assessment form, and retrospectively, using hospital records, from patients with suspected COVID-19, and reviewed hospital records at 30 days for adverse outcome (death or receiving organ support). Patients with post-exertion oxygen saturation recorded were selected for this analysis. We constructed receiver-operating characteristic curves, calculated diagnostic parameters, and developed a multivariable model for predicting adverse outcome. RESULTS: We analysed data from 817 patients with post-exertion oxygen saturation recorded after excluding 54 in whom measurement appeared unfeasible. The c-statistic for post-exertion change in oxygen saturation was 0.589 (95% CI 0.465 to 0.713), and the positive and negative likelihood ratios of a 3% or more desaturation were, respectively, 1.78 (1.25 to 2.53) and 0.67 (0.46 to 0.98). Multivariable analysis showed that post-exertion oxygen saturation was not a significant predictor of adverse outcome when baseline clinical assessment was taken into account (p=0.368). Secondary analysis excluding patients in whom post-exertion measurement appeared inappropriate resulted in a c-statistic of 0.699 (0.581 to 0.817), likelihood ratios of 1.98 (1.26 to 3.10) and 0.61 (0.35 to 1.07), and some evidence of additional prognostic value on multivariable analysis (p=0.019). CONCLUSIONS: Post-exertion oxygen saturation provides modest prognostic information in the assessment of selected patients attending the emergency department with suspected COVID-19. TRIAL REGISTRATION NUMBER: ISRCTN Registry (ISRCTN56149622) http://www.isrctn.com/ISRCTN28342533.

Cost-effectiveness of out-of-hospital continuous positive airway pressure for acute respiratory failure: decision analytic modelling using data from a feasibility trial.

BACKGROUND: Standard prehospital management for Acute respiratory failure (ARF) involves controlled oxygen therapy. Continuous positive airway pressure (CPAP) is a potentially beneficial alternative treatment, however, it is uncertain whether this could improve outcomes and provide value for money. This study aimed to evaluate the cost-effectiveness of prehospital CPAP in ARF. METHODS: A cost-utility economic evaluation was performed using a probabilistic decision tree model synthesising available evidence. The model consisted of a hypothetical cohort of patients in a representative ambulance service with undifferentiated ARF, receiving standard oxygen therapy or prehospital CPAP. Costs and quality adjusted life years (QALYs) were estimated using methods recommended by NICE. RESULTS: In the base case analysis, using CPAP effectiveness estimates form the ACUTE trial, the mean expected costs of standard care and prehospital CPAP were £15,201 and £14,850 respectively and the corresponding mean expected QALYs were 1.190 and 1.128, respectively. The mean ICER estimated as standard oxygen therapy compared to prehospital CPAP was £5685 per QALY which indicated that standard oxygen therapy strategy was likely to be cost-effective at a threshold of £20,000 per QALY (67% probability). The scenario analysis, using effectiveness estimates from an updated meta-analysis, suggested that prehospital CPAP was more effective (mean incremental QALYs of 0.157), but also more expensive (mean incremental costs of £1522), than standard care. The mean ICER, estimated as prehospital CPAP compared to standard care, was £9712 per QALY. At the £20,000 per QALY prehospital CPAP was highly likely to be the most cost-effective strategy (94%). CONCLUSIONS: Cost-effectiveness of prehospital CPAP depends upon the estimate of effectiveness. When based on a small pragmatic feasibility trial, standard oxygen therapy is cost-effective. When based on meta-analysis of heterogeneous trials, CPAP is cost-effective. Value of information analyses support commissioning of a large pragmatic effectiveness trial, providing feasibility and plausibility conditions are met.

Implementation of rapid rule out of myocardial infarction using high-sensitivity troponin: cross-sectional survey of English hospitals.

OBJECTIVES: Recent guidance recommended use of high-sensitivity troponin for rapid rule out of myocardial infarction (MI) in the English health service. We aimed to determine the extent of implementation of this guidance across English hospitals. METHODS: This study conducted a cross-sectional questionnaire survey of 131 English acute hospitals with over 10 000 admissions per year. RESULTS: We received 125/131 responses (95%), with 110/125 (88%) reporting use of a high-sensitivity troponin assay and responses showing progressive implementation over the last 10 years. High-sensitivity troponin was reported to be used for rapid rule out of MI in 92/110 Trusts (84%). Review of guidelines received from 95/110 Trusts identified that 71/95 (75%) provided guidance for rapid MI rule out with high-sensitivity troponin: 57 recommended testing at 0 and 3 hours, 4 recommended testing at 0 and 2 hours, and 9 recommended testing at 0 and 1 hour, and timing was unclear at one Trust. CONCLUSIONS: English acute hospital Trusts report widespread implementation of high-sensitivity troponin for rapid rule out of MI, with most recommending testing at 0 and 3 hours.