Introduction
Symptoms suggestive of myocardial infarction (MI) are a major reason for presentation to the emergency departments (ED) worldwide [
1]. Measurement of cardiac troponin is crucial to diagnose or to rule out non-ST-elevation MI (NSTEMI) [
2,
3]. For the management of patients with suspected NSTEMI, current guidelines recommend the application of high-sensitivity cardiac troponin (hs-cTn) assay-specific thresholds such as the 99th percentile or study-derived cut-offs for measurements obtained directly at presentation and, depending on the selected diagnostic approach, during serial sampling after one, two or three hours. [
3‐
7]
Application of fixed assay-specific hc-cTn thresholds combined with predefined time points of serial sampling remains challenging in busy emergency settings with globally widely differing patients’ characteristics. Besides, in the context of suspected NSTEMI, clinicians do not interpret hs-cTn concentrations and thresholds in isolation, but in combination with ECG findings and clinical characteristics, such as chest pain onset time, cardiovascular risk factors, age, sex, and other comorbidities, which are largely neglected in most current diagnostic algorithms [
8]. Thus, a diagnostic algorithm, simultaneously including various variables such as hs-cTn concentrations, their dynamic change during flexibly timed resampling, ECG findings as well as most relevant and immediately available clinical variables, constitutes an unmet clinical need in patients with suspected MI, both in the ED and in the ambulatory care setting.
Based on prior work [
9], we derived and validated a machine-learning model, which estimates the individual probability of NSTEMI in patients presenting with symptoms indicative of MI. This model accounts for immediately available confounding clinical variables, allows for flexible timing of potential serial sampling and can be applied using most established hs-cTn assays, including point-of-care assays. We aimed to prove its clinical application in patients with suspected NSTEMI and [
1] defined the model’s overall diagnostic accuracy, [
2] assessed the clinical performance according to MI probability thresholds in heterogeneous clinical conditions, and [
3] finally compared the model’s clinical utility against currently recommended assay-specific thresholds. Overall, this work shall pave the way towards the routine clinical implementation of medical decision support systems to improve a rapid, efficient and safe diagnostic process in patients with suspected MI.
Discussion
Extending prior work [
9], we derived, validated, and generalized a personalized diagnostic model to immediately, accurately, and safely quantify the risk probability of MI. From individual-level data contributed by more than 27,000 patients with suspected acute MI in four continents, nine countries and 14 prospectively established real world cohorts we applied various machine-based learning tools and developed a super learner model resulting in two diagnostic models. Their clinical application allows providers to determine the probability of MI with high diagnostic accuracy. The personalized model (1) works irrespective of which hs-cTn assay is used, (2) integrates the information of important and rapidly available clinical variables, (3) requires neither assay-specific cut-offs nor fixed timing of serial sampling, (4) can be applied after calibration in various clinical settings with widely varying pre-test probabilities and (5) offers a selection of risk probability thresholds (e.g., 0.5%, 1% or 2% MI probability) which allows for safe and immediate discharge in a very high proportion of patients.
While the application of hs-cTn assays improves visibility of even minor myocardial injury and allows for early detection of MI, the clinical management and decision-making became more challenging [
4,
13,
15]. Consequently, various assay-specific hs-cTn algorithms have been developed and implemented to efficiently diagnose and triage patients with suspected MI [
16‐
18]. Although these algorithms allow for major advances in rapid and safe clinical decision-making, they still rely on inflexible rules for the timing of hs-cTn resampling (1, 2 or 3 h) and apply assay-specific thresholds of mostly very low concentrations and do not account for clinical variables such as age, sex, risk factors, chest pain onset time, and others. In consequence, the assay-specific 0/1 h and 0/2 h or 0/3 h algorithms as suggested by the European Society of Cardiology for example, are not fully implemented in global clinical routine [
4].
To accelerate the advantage of hs-cTn usage in clinical routine and enable—in interaction with hs-cTn point-of-care tests—a safe application also in ambulatory settings, we extend the concept of risk probabilities introduced recently [
9] towards a highly accurate personalized diagnostic model. As the model was trained using eleven (selected out of an initial 18) clinical variables including time of chest pain onset, time between serial sampling, ECG, age, sex, and cardiovascular risk factors and nearly all hs-cTn tests currently available, it provides the highest possible diagnostic accuracy and allows for rapid and safe decision-making. Both, single and serial sampling models achieve excellent diagnostic accuracy and offer the opportunity to select rule-out thresholds which allow rapid and safe discharge in a high proportion of patients. To achieve the best balance between high safety and high efficacy, a low MI probability threshold (e.g., 0.5%, 1% or 2%) is recommended for rule-out after single or serial testing, respectively. Compared with previous data on the performance of the ESC 0/1 h algorithm reporting a rule-out proportion of 44–57%, the rule-out proportions achieved by the application of the thresholds of the diagnostic models are larger and range, e.g., for a serial rule-out cut-off < 2%, between 60 and 76% [
18,
19]. This improvement is most apparent for a single measurement approach, which allows direct rule-out of MI in 30–49% of the overall population compared to 13–15% using the ESC algorithm [
18‐
22].
As the model is based on heterogenous global data, it is calibrated for European, Australian, New Zealand, Northern American, and Japanese conditions and, therefore, can be generally applied. The model also integrates two point-of-care hs-cTn assays (Pathfast and Atellica VTLi). When hs-cTn point-of-care assays are used, the ARTEMIS model can be applied in outpatient settings and, therefore, might improve diagnostic accuracy and speed in outpatient care and could reduce the number of hospital admissions.
In general, machine-based learning diagnostic and prediction models need to fulfill high methodological, clinical and regulatory standards before being used by healthcare professionals in clinical practice [
23]. A recent report raises 12 critical questions, all of which have been positively addressed by the current algorithm [
23]. In particular, the sample size is appropriate, validation has been extensively performed, and the outcome variable is labeled reliable, replicable, and independent.
Prior work already introduced machine-learning concepts to provide an individualized and objective assessment of the likelihood of myocardial infarction [
24]. It for the first time presented the concept of machine-based learning to improve the diagnostic accuracy of MI diagnosis and rule-out. Although this work paved the way towards modern diagnostic approaches and performs well in routine clinical practice [
25], it relies on only two predefined clinical variables age and sex beyond hs-cTn, and it is restricted to one specific hs-cTnI assay. It further highlights the need for model calibration prior to application in the population, which was limited in this the first concept [
25]. The ARTEMIS model had been calibrated for the heterogeneous clinical conditions globally but requires further calibration of the super learner for each clinical setting, in which it will be directly applied. In consequence, the concept and construction of the ARTEMIS model will enable both, the inclusion of any hs-cTn assay entering the market and local calibration to settings in which it will be clinically applied.
The integration of the selected, easily available variables including whatever hs-cTn test available, supports an app- or middleware-guided safe, efficient and immediate medical decision. Whereas the ARTEMIS pathway might be suitable for embedded middleware approaches, which enable the integration into the hospital-based electronic health record system, app-based solutions might be more suitable for ambulatory care or independent emergency settings.
Some limitations should be considered when interpreting the findings. First, the outcome diagnoses of MI were adjudicated in each cohort separately and were not based on a harmonized standard operating procedure. Second, our models were validated to estimate the individual risk of MI in patients with clinically suspected MI. This does not include other acute conditions, that may lead to acute chest pain, such as pulmonary embolism or aortic dissection. Therefore, the estimated MI probabilities must always be considered in the clinical context and should not be used as only basis for decision-making. Finally, our diagnostic models were derived, validated, and generalized using data from multiple prospective, diagnostic studies, but have not been prospectively tested in clinical routine. Therefore, to assess real-world performance not only in the ED but also in other clinical settings (e.g., in ambulatory care or in the preclinical setting in ambulances), prospective clinical trials directly applying the ARTEMIS diagnostic model and comparing against standard of care is of importance.
In conclusion, we developed, validated, and globally applied the easily applicable diagnostic ARTEMIS model considering immediately available variables to estimate the individual risk of MI in patients with suspected MI. The model can be used with most hs-cTn assays currently available and allows for rapid and safe discharge of a very high proportion of patients. Its digital application might improve routine clinical practice globally and enable a personalized diagnostic evaluation of suspected MI.
Acknowledgements
The ARTEMIS study group: Emily Brownlee: Royal Brisbane and Women’s Hospital, Metro North Hospital and Health Service, Brisbane, Queensland, Australia, Kai M. Eggers: Department of Medical Sciences, Uppsala University, Uppsala, Sweden, Gavin Fincher: The Prince Charles Hospital, Metro North Hospital and Health Service, Brisbane, Queensland, Australia, Norbert Frey: Department of Cardiology, Heidelberg University Hospital, Heidelberg, Germany, Niranjan Gaikwad: The Prince Charles Hospital, Metro North Hospital and Health Service, Brisbane, Queensland and School of Clinical Medicine, University of Queensland, Australia, Vinay Gangathimmaiah: Emergency Department, The Townsville Hospital, Townsville, QLD, Australia and School of Medicine, James Cook University, Australia, Emma Hall: Department of Emergency Medicine, Gold Coast University Hospital, Gold Coast, QLD, Australia, Paul M. Haller: Department of Cardiology, University Heart and Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, Christian Hamilton-Craig: The Prince Charles Hospital, Metro North Hospital and Health Service, Brisbane, Queensland, Faculty of Medicine, University of Queensland and School of Medicine, Griffith University, Sunshine Coast, QLD, Australia, Rebecca Hancock: Emergency Department, The Townsville Hospital, Townsville, QLD, Australia, Andrew Hobbins-King: The Sunshine Coast Hospital, Caloundra, Queensland and School of Medicine, Griffith University, Gold Coast, QLD, Australia, Gerben Keijzers: Department of Emergency Medicine, Gold Coast University Hospital, Gold Coast, QLD, Australia, School of Medicine, Griffith University, Gold Coast, QLD, Australia and Faculty of Health Sciences and Medicine, Bond University, Gold Coast, QLD, Australia, Maryam Khorramshahi Bayat: The Prince Charles Hospital, Metro North Hospital and Health Service, Brisbane, Queensland and School of Clinical Medicine, University of Queensland, Australia, Georgios Koliopanos: Cardio-CARE, Medizincampus Davos, Davos, Switzerland, Jonas Lehmacher: Department of Cardiology, University Heart and Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, Lina Ljung: Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden, Troy Madsen: Department of Emergency Medicine, University of Utah, Ehsan Mahmoodi: The Prince Charles Hospital, Metro North Hospital and Health Service, Brisbane, Queensland, School of Clinical Medicine, University of Queensland and Faculty of Health Sciences and Medicine, Bond University, Gold Coast, QLD, Australia, Ellyse McCormick: Royal Brisbane and Women’s Hospital, Metro North Hospital and Health Service, Brisbane, Queensland, Australia, Bryn Mumma: Department of Emergency Medicine, University of California-Davis, Richard Nowak: Department of Emergency Medicine, Henry Ford Health, Siegfried Perez: Logan Hospital, Metro South Hospital and Health Service, Brisbane, Queensland, Australia, Vazhma Qaderi: Department of Cardiology, University Heart and Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, Isuru Ranasinghe: The Prince Charles Hospital, Metro North Hospital and Health Service, Brisbane, Queensland and School of Clinical Medicine, University of Queensland, Australia, Alina Schock: Department of Cardiology, University Heart and Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, Nils A. Sörensen: Department of Cardiology, University Heart and Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, Andrew Staib: Princess Alexandra Hospital, Metro South Hospital and Health Service, Brisbane, Queensland and School of Clinical Medicine, University of Queensland, Australia, Laura Stephensen: Royal Brisbane and Women’s Hospital, Metro North Hospital and Health Service, Brisbane, Queensland and School of Public Health and Social Work, Queensland University of Technology, Michael Weaver: University of Florida College of Nursing, R. Gentry Wilkerson: Department of Emergency Medicine, University of Maryland School of Medicine, and Anna Zournazi: Pathology Queensland, Australia.
Declarations
Conflict of interest
SB receives fundings from Abbott Diagnostics, Bayer, SIEMENS, Amgen and NOVARTIS as well as honoraria for lectures and/or chairs from Abbott, Abbott Diagnostics,, AMGEN, Astra Zeneca, Bayer, Boehringer Ingelheim, BMS (Bristol Meyer Squib), Daiichi Sankyo, LumiraDx, NOVARTIS and Thermo Fisher. SB is a member of advisory boards and consultant of Thermo Fisher. JTN, RT, FO, TZ, AZ and SB are co-founders and shareholders of the ART-EMIS Hamburg GmbH, which holds an international patent application on the use of a computing device to estimate the probability of myocardial infarction (Publication Numbers WO2022043229A1, TW202219980A). JTN reports speaker honoraria/consulting honoraria from PHC, Roche and Siemens. RT reports research support from the Kühne Foundation, the Swiss National Science Foundation (Grant No P300PB_167803), the Swiss Heart Foundation, the Swiss Society of Cardiology and speaker honoraria/consulting honoraria from Abbott, Amgen, Astra Zeneca, Roche, Siemens, and Singulex. BRA receives research funding/support from Roche Diagnostics, Siemens, and Beckman Coulter. BRA is a consultant for Roche Diagnostics. FSA is a consultant for HyTest Ltd and an associate Editor for Clinical Chemistry. FSA is part of the advisory boards of Werfen, Siemens Healthineers, Qorvo and AWE Medical Group. FSA receives honorarium for speaking at industry conferences of Siemens Healthineers and Beckman Coulter. FSA is PI on Industry Funded Grants (non-salaried) on cardiac biomarkers through Hennepin Healthcare Research Institute for Abbott Diagnostics, Abbott POC, BD, Beckman Coulter, Ortho-Clinical Diagnostics, Roche Diagnostics, Siemens Healthcare, ET Healthcare and Qorvo. RHC is a consultant for and receives funding/support from Roche Diagnostics, Siemens Healthineers, Beckman Coulter Diagnostics, Becton Dickinson and Co, Quidel Corp, and Sphingotec GMBH. LC reports research funding from Siemens, Abbott, and Beckman. EG reports personal fees from Bayer Vital, personal fees from Astra Zeneca, personal fees from Roche Diagnostics, personal fees from Brahms Germany, personal fees from Daiichi Sankyo, personal fees from Lilly Deutschland, outside the submitted work. EG reports participation on a Data Safety. Monitoring Board or Advisory Board at Boehringer Ingelheim and Roche Diagnostics. JG receives grants from Siemen´s Point of Care and Beckman Coulter. KI receives grants from Japanese KAKENHI (grant number JP18K09554). KI reported payment for honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from Roche Diagnostics to Fujirebio Inc. PK reports support for this manuscript to his institution from Canadian Institutes of Health Research, Abbott Diagnostics and Roche Diagnostics. PK reports grants for his institution from Abbott Diagnostics, Roche Diagnostics, Randox laboratories, Beckman Coulter, Ortho Clinical Diagnostics and Siemens Healthcare Diagnostics. PK receives consulting fees from Abbott, Beckman Coulter, Roche Diagnostics, Quidel and Siemens Healthcare. PK receives reports honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from Beckman Coulter, Roche Diagnostics, Siemens Healthcare and Thermo Fisher Scientific. PK receives support for attending meetings and/or travel from Randox Laboratories ans Roche Diagnostics. McMaster University has filed a patent with PK listed as an inventor in the acute cardiovascular biomarker field, in particular, a patent has been awarded in Europe (EP 3 341 723 B1) on a Method of determining risk of an adverse cardiac event. McMaster University has also filed patents with PK listed as an inventor on Quality Control Materials for Cardiac Troponin Testing and Identifying pregnant women at increased risk for hypertension and future cardiovascular disease. PK reports participation on a Data Safety Monitoring Board or Advisory Board for Roche Diagnostics, Siemens Healthcare Diagnostics, Beckman Coulter and Quidel. BL is a member (unpaid) of Study Group on Biomarkers of the ESC Association for Acute CardioVascular Care. SAM receives research funding/support from Roche Diagnostics, Abbott Laboratories, Ortho Clinical Diagnostics, Creavo Medical Technologies, Siemens, Pathfast, Grifols, Rigel Pharmaceuticals, the Agency for Healthcare Research and Quality, the Patient-Centered Outcomes Research Institute, the National Heart, Lung, and Blood Institute (1 R01 HL118263-01), and the Health Resources and Services Administration (1 H2ARH399760100). Dr Mahler is a consultant for Roche Diagnostics and Amgen and is the chief medical officer for Impathiq Inc. NLM reported grants from British Heart Foundation to his institution (CH/F/21/90010, RG/20/10/34966, RE/18/5/34216). NLM has received honoraria or consultancy from Abbott Diagnostics, Roche Diagnostics, Siemens Healthineers, and LumiraDx. NLM reports participation on an Advisory Board of LumiraDx, Roche Diagnostics and Siemens Healthineers. NLM is supported by a Chair Award, Programme Grant, Research Excellence Award (CH/F/21/90010, RG/20/10/34966, RE/18/5/34216) from the British Heart Foundation. JWP has received non-directed funds from Abbott Diagnostics, Roche, Siemens within the last 5 years and consulted for Abbott. CJP receives Project grants from the Health Research Council of New Zealand and from the Heart Foundation of New Zealand. He is PI on grants hosted by University of Otago. CJP received project grant from the Ministry of Business, Innovation and Employment, New Zealand. CJP is inventor on patents (granted and filed) for the diagnosis of acute coronary syndromes. CJP is CSO at Upstream Medical Technologies. CJP reported research support from Upstream Medical Technologies and from Biovendor R&D. AMR reports speaker honoraria/advisory board fees and research grants in kind and/or cash funding from Roche Diagnostics, Astra Zeneca, Abbott Laboratories, Novartis, NovoNordisk, Thermo Fisher, Critical Diagnostics, Sphingotec, Medtronic and Boston Scientific. AMR reports grants from National Medical Council of Singapore and NovoNordisk research grants. He has received publicly contestable funding from the New Zealand Health Research Council, NZ Heart Foundation and the National Medical research Council of Singapore. AMR reports personal fees from Roche Diagnostics, Novartis and Roche Diagnostics. AMR reports participation on a Data Safety Monitoring Board or Advisory Board in the Pontiac 2 trial and STAREE Trial. YS has previously served on Advisory Boards for Roche Diagnostics and Abbott Diagnostics. YS has also been a speaker for Abbott Diagnostics. WP reported research grants and consulting fees to his institution from Siemens Healthineers. MPT received Funding for clinical research from Abbott, Alere, Beckman, Radiometer and Roche (to his institution). MPT received payment for speaking from Abbott, Alere, and Roche as well as Consulting fees from Abbott, Roche and Siemens. MPT received payment for participation in advisory boards from Abbott, Radiometer, Roche and Siemens as well as funding for education from Abbott, Alere and Beckman (to his institution). BT receives a project-related grant from German Heart foundation and from the Ernst und Berta Grimmke-Stiftung. RWT received payments to his institution from Health Research Council of NZ, Heart Foundation of NZ, American Regent, Merck and Bayer. RWT receives consulting fees from American Regent, Merck, Bayer and Roche Diagnostics.AW is having a patent on the Clinical Chemistry Score. TZ is supported by the German Centre for Cardiovascular Research (DZHK e.V.) grant numbers 81Z1710101 and 81Z0710102.TZ is supported by EU Horizon 2020 programme and EU ERANet and ERAPreMed Programmes.