Point-of-Care Troponin Testing during Ambulance Transport to Detect Acute Myocardial Infarction

A New Chemiluminescence-Based Rapid Diagnostic Testing Platform with Sequential Dual-Flow Strips for Cardiac Troponin I (cTnI)

Although the most commonly used method for enhancing a limit of detection (LoD) in immunoassay is adopting chemiluminescence (CL), the liquid form of CL substrates has hindered its use for rapid diagnostic testing (RDT). In order to use the CL-based immunoassay in RDT with minimal user intervention, the liquid CL substrate should be converted to a dry form. In addition, a new RDT platform that is able to perform two sequential flows needs to be developed for the sequential flow control of the CL substrate. In this work, we have successfully developed a new dry form of CL substrate on the strip using a lyophilization process, as well as new lateral flow strips using an additional membrane pad for a time delay to achieve the desired sequential dual flows. Thus, on the dual-flow RDT strips, first the detection antibody conjugated with an enzyme flows over the test and control lines, and then the reconstituted CL substrate flows later. A hydrophilic PVDF membrane was selected as a pad material for the time delay to achieve the sequential dual flows through two flow paths, and flow introduction timing was functionally controlled to secure the time delay of approximately 5 minutes desired between the two flows. A CL-based cardiac troponin I (cTnI) assay was successfully performed on the new dual-flow RDT platform with a sample volume of 120 μL, achieving a LoD of 100 pg/mL. The achieved LoD is better than those possible with most of the currently available RDTs on the market. The new CL-based RDT platform with the capability of dual flows developed in this work can be used for numerous other immunodiagnostic platforms which need further high-sensitivity detection, envisaging a new RDT platform for point-of-care testing with further quantitative analysis.

The development of a decision support tool in the prehospital setting for acute chest pain - a study protocol for an observational study (BRIAN2)

INTRODUCTION

Chest pain is one of the most common reasons for contacting the emergency medical services (EMS). It is difficult for EMS personnel to distinguish between patients suffering from a high-risk condition in need of prompt hospital care and patients suitable for non-conveyance. A vast majority of patients with chest pain are therefore transported to the emergency department (ED) for further investigation even if hospital care is not necessary. Improved prehospital assessment and risk stratification, thus accurately and safely identifying patients suitable for non-conveyance, could prevent unnecessary transport to the ED. This would reduce ED crowding and overburdening sparse EMS resources. It would thus also probably reduce healthcare costs. Little is known about the prehospital use of the 5th generation, i.e. high-sensitivity troponin analyses. The aim of this project is to develop an EMS decision support tool using high-sensitivity troponin I for risk assessment of chest pain patients.

METHODS AND ANALYSIS

This is a prospective, multicentre, cohort study including adult unselected EMS patients with chest pain. Data is being collected from 20 May 2023 to 31 December 2025, aiming to include at least 2,000 patients. High-sensitivity troponin I is being analysed bedside using Siemens Healthineers Atellica VTLi. In addition to prehospital troponin I, data is being collected on patient medical history, onset, vital signs, symptoms, ECG and diagnosis at hospital discharge. Several statistical analyses (random forest, logistic regression, gradient boosting) will be conducted to identify the best model for identifying patients with low-risk conditions suitable for non-conveyance.

ETHICS AND DISSEMINATION

The study has been approved by the Swedish Ethical Review Authority (Dnr 2022-01066-01 and 2022-06846-02). Patients are being informed about the study both orally and in writing. The results of the study will be published in a peer-reviewed journal and will be presented at national and/or international conferences.

REGISTRATION DETAILS

The study is registered at ClinicalTrials.gov (NCT05767619).

Smartphone-Enabled Point-of-Care Testing for Prehospital Stroke Diagnosis

OBJECTIVES

The objective of this study was to evaluate the feasibility of point-of-care testing (POCT) devices for N-terminal pro-B-type natriuretic peptide (NT-proBNP) measurement in prehospital settings, with the aim of improving the speed and accuracy of stroke diagnosis, thereby facilitating quicker and more effective patient care.

METHODS

Prehospital blood samples were collected from suspected stroke patients, and NT-proBNP levels were measured using a POCT device in ambulances and hospitals. Results from the NT-proBNP POCT and smartphone images were analyzed. Plasma samples underwent Elecsys proBNP II immunoassay after storage at -80ºC.

RESULTS

A total of 121 suspected stroke patients were included in the study. The correlation between POCT measured by the POCT and immunoassay for NT-proBNP was strong (R = 0.926). Smartphone images also strongly correlated with POCT values at 10 min (R²=0.9716) and 15 min (R²=0.9405). Stability analysis of samples showed consistent NT-proBNP results and a high correlation (R = 0.907) was observed between plasma and whole blood samples for NT-proBNP POCT.

CONCLUSIONS

This study highlights the potential of NT-proBNP POCT devices in ambulances to expedite stroke diagnosis and management within 10 min. Smartphone integration further enhances efficiency, adding advancement in prehospital stroke management.

How Close Are We to Patient-Side Troponin Testing?

Laboratory-based high-sensitivity cardiac troponin testing has been the pillar for emergency stratification of suspected acute coronary syndrome for well over a decade. Point-of-care troponin assays achieving the requisite analytical sensitivity have recently been developed and could accelerate such assessment. This review summarises the latest assays and describes their potential diverse clinical utility in the emergency department, community healthcare, pre-hospital, and other hospital settings. It outlines the current clinical data but also highlights the evidence gap, particularly the need for clinical trials using whole blood, that must be addressed for safe and successful implementation of point-of-care troponin analysis into daily practice. Additionally, how point-of-care troponin testing can be coupled with advances in biosensor technology, cardiovascular screening, and triage algorithms is discussed.

Correlation Between EtCO2 and PCO2 in Patients Undergoing Critical Care Transport

OBJECTIVES

End-tidal carbon dioxide (EtCO2) monitoring is widely used as a surrogate for the partial pressure of carbon dioxide (PCO2) in critically ill patients receiving manual or mechanical ventilation in prehospital, emergency, and critical care settings. Specific targets for ETCO2 are a key component of Emergency Medical Services (EMS) protocols, especially for specific patient groups such as those with traumatic brain injury. However, the correlation between EtCO2 and venous or arterial PCO2 is uncertain. We aimed to assess the correlation between EtCO2 and PCO2 in intubated patients undergoing critical care transport (CCT), and in specific subgroups of patients.

METHODS

We performed a retrospective review of patients undergoing emergency transport by a multi-state CCT agency. Patients were included if they had an advanced airway and both an EtCO2 and PCO2 reading within 5 min of each other. We obtained data on patient demographics, transport characteristics, medical categories, vital signs, lab values, and specific interventions. We performed univariable and multivariable binary logistic regression to assess the association between delta PCO2 and these characteristics.

RESULTS

We included 6,459 patients (mean age 58.4 years [SD 18.5], 57.1% male), of which a subset of 551 patients had multiple EtCO2-PCO2 measurements within 5 min. The median (IQR) initial delta PCO2 was 12.9 mmHg (7.1, 21.9). 3,967 (61.4%) patients had a delta PCO2 >10 mmHg and 1,843 (28.5%) had a delta PCO2 >20 mmHg. We identified an independent association between delta PCO2 >10 mmHg and age, male sex, interfacility transport, venous sampling site, respiratory rate, hypotension, hypoxia, and thoracostomy. In patients with multiple blood gas measurements, 76% had delta PCO2 >10 mmHg over the duration of the transport.

CONCLUSIONS

We identified substantial differences between EtCO2 and PCO2 across patients with medical and traumatic conditions undergoing critical care transport. The PCO2 assessment should be strongly considered as part of ventilatory management in patients encountered in emergency and critical care settings.

Prehospital management and outcomes of patients calling with chest pain as the main complaint

BACKGROUND

Chest pain is a frequent cause of health care contacts. We examined the prehospital management, in-hospital discharge diagnoses, and mortality of patients calling a non-emergency and emergency medical service with chest pain.

METHODS

The Copenhagen Emergency Medical Services (EMS) consists of a non-emergency medical helpline (calls to 1813) and emergency medical service (1-1-2 calls). We included all calls to the Copenhagen EMS with a primary complaint of chest pain from 2014 to 2018 in Copenhagen, Denmark. The outcomes were: emergency response (ambulance dispatch, other transports/self-transport/home visits, self-care, and unknown/cancelled response), in-hospital diagnosis within 7 days after the call (cardiovascular, pulmonary, or other non-cardiovascular/pulmonary) and 30-day mortality.

RESULTS

Among 4,834,071 calls, 91,671 were registered with chest pain at the Copenhagen EMS. The first call for each patient was kept for analysis (n = 66,762). In total, 91.4% were referred to the hospital, 75.8% (n = 50,627) received an ambulance and 15.6% (n = 10,383) received other transport/self-transport/home visits. Overall, 26.9% (n = 17,937) were diagnosed with a cardiovascular disease, 5.2% (n = 3,490) a pulmonary disease, 52.8% (n = 35.242) other non-cardiovascular/pulmonary disease, and 15.1% (n = 10,093) received no diagnosis. Among ambulance-transported patients, the prevalence of cardiovascular discharge diagnoses was higher (32.1%) and fewer received no diagnosis (11.0%). Cardiovascular disease was less prevalent among patients not transported by ambulance and patients not referred to hospital at all (2-13.4%) and in patients ≤ 40 years of age (< 10%). The 30-day mortality was below 5% regardless of diagnosis (0.6-4%), and 65,704 (98.4%) were still alive 30 days later.

CONCLUSION

Nearly all patients calling with chest pain were referred for treatment. Among ambulance-transported patients, around half of the patients did not have a cardiovascular/pulmonary disease. While current practices appear reasonable, improved differentiation of chest pain patients in telephone consultations could potentially both improve the treatment and management of these patients and reduce the in-hospital burden of non-acute chest pain consultations.

Deep Learning-Enhanced Paper-Based Vertical Flow Assay for High-Sensitivity Troponin Detection Using Nanoparticle Amplification

Successful integration of point-of-care testing (POCT) into clinical settings requires improved assay sensitivity and precision to match laboratory standards. Here, we show how innovations in amplified biosensing, imaging, and data processing, coupled with deep learning, can help improve POCT. To demonstrate the performance of our approach, we present a rapid and cost-effective paper-based high-sensitivity vertical flow assay (hs-VFA) for quantitative measurement of cardiac troponin I (cTnI), a biomarker widely used for measuring acute cardiac damage and assessing cardiovascular risk. The hs-VFA includes a colorimetric paper-based sensor, a portable reader with time-lapse imaging, and computational algorithms for digital assay validation and outlier detection. Operating at the level of a rapid at-home test, the hs-VFA enabled the accurate quantification of cTnI using 50 μL of serum within 15 min per test and achieved a detection limit of 0.2 pg/mL, enabled by gold ion amplification chemistry and time-lapse imaging. It also achieved high precision with a coefficient of variation of <7% and a very large dynamic range, covering cTnI concentrations over 6 orders of magnitude, up to 100 ng/mL, satisfying clinical requirements. In blinded testing, this computational hs-VFA platform accurately quantified cTnI levels in patient samples and showed a strong correlation with the ground truth values obtained by a benchtop clinical analyzer. This nanoparticle amplification-based computational hs-VFA platform can democratize access to high-sensitivity point-of-care diagnostics and provide a cost-effective alternative to laboratory-based biomarker testing.

Prehospital Targeting of 1-Year Mortality in Acute Chest Pain by Cardiac Biomarkers

The identification and appropriate management of patients at risk of suffering from acute chest pain (ACP) in prehospital care are not straightforward. This task could benefit, as occurs in emergency departments (EDs), from cardiac enzyme assessment. The aim of the present work was to derive and validate a scoring system based on troponin T (cTnT), N-terminal pro B-type natriuretic peptide (NT-proBNP), and D-dimer to predict 1-year mortality in patients with ACP. This was a prospective, multicenter, ambulance-based cohort study of adult patients with a prehospital ACP diagnosis who were evacuated by ambulance to the ED between October 2019 and July 2021. The primary outcome was 365-day cumulative mortality. A total of 496 patients fulfilled the inclusion criteria. The mortality rate was 12.1% (60 patients). The scores derived from cTnT, NT-proBNP, and D-dimer presented an AUC of 0.802 (95% CI: 0718-0.886) for 365-day mortality. This AUC was superior to that of each individual cardiac enzyme. Our study provides promising evidence for the predictive value of a risk score based on cTnT, NT-proBNP, and D-dimer for the prediction of 1-year mortality in patients with ACP. The implementation of this score has the potential to benefit emergency medical service care and facilitate the on-scene decision-making process.

Frequency, compliance, and yield of cardiac testing after high-sensitivity troponin accelerated diagnostic protocol implementation

BACKGROUND

Among persons presenting to the emergency department with suspected acute myocardial infarction (MI), cardiac troponin (cTn) testing is commonly used to detect acute myocardial injury. Accelerated diagnostic protocols (ADPs) guide clinicians to integrate cTn results with other clinical information to decide whether to order further diagnostic testing.

OBJECTIVE

To determine the change in the rate and yield of stress test or coronary CT angiogram following cTn measurement in patients with chest pain presenting to the emergency department pre- and post-transition to a high-sensitivity (hs-cTn) assay in an updated ADP.

METHODS

Using electronic health records, we examined visits for chest pain at five emergency departments affiliated with an integrated academic health system 1-year pre- and post-hs-cTn assay transition. Outcomes included stress test or coronary imaging frequency, ADP compliance among those with additional testing, and diagnostic yield (ratio of positive tests to total tests).

RESULTS

There were 7564 patient-visits for chest pain, including 3665 in the pre- and 3899 in the post-period. Following the updated ADP using hs-cTn, 862 (23.5 per 100 patient visits) visits led to subsequent testing versus 1085 (27.8 per 100 patient visits) in the pre-hs-cTn period, (P < 0.001). Among those who were tested, the protocol-compliant rate fell from 80.9% to 46.5% (P < 0.001), but the yield of those tests rose from 24.5% to 29.2% (P = 0.07). Among tests that were noncompliant with ADP guidance, yield was similar pre- and post-updated hs-cTn ADP implementation (pre 13.0%, post 15.4% (P = 0.43).

CONCLUSION

Implementation of hs-cTn supported by an updated ADP was associated with a lower rate of stress testing and coronary CT angiogram.

Strategies to mitigate emergency department crowding and its impact on cardiovascular patients

Emergency department (ED) crowding is a worsening global problem caused by hospital capacity and other health system challenges. While patients across a broad spectrum of illnesses may be affected by crowding in the ED, patients with cardiovascular emergencies-such as acute coronary syndrome, malignant arrhythmias, pulmonary embolism, acute aortic syndrome, and cardiac tamponade-are particularly vulnerable. Because of crowding, patients with dangerous and time-sensitive conditions may either avoid the ED due to anticipation of extended waits, leave before their treatment is completed, or experience delays in receiving care. In this educational paper, we present the underlying causes of crowding and its impact on common cardiovascular emergencies using the input-throughput-output process framework for patient flow. In addition, we review current solutions and potential innovations to mitigate the negative effect of ED crowding on patient outcomes.

Risk stratification tools for patients with syncope in emergency medical services and emergency departments: a scoping review

BACKGROUND

Patients with a syncope constitute a challenge for risk stratification in (prehospital) emergency care. Professionals in EMS and ED need to differentiate the high-risk from the low-risk syncope patient, with limited time and resources. Clinical decision rules (CDRs) are designed to support professionals in risk stratification and clinical decision-making. Current CDRs seem unable to meet the standards to be used in the chain of emergency care. However, the need for a structured approach for syncope patients remains. We aimed to generate a broad overview of the available risk stratification tools and identify key elements, scoring systems and measurement properties of these tools.

METHODS

We performed a scoping review with a literature search in MEDLINE, CINAHL, Pubmed, Embase, Cochrane and Web of Science from January 2010 to May 2022. Study selection was done by two researchers independently and was supervised by a third researcher. Data extraction was performed through a data extraction form, and data were summarised through descriptive synthesis. A quality assessment of included studies was performed using a generic quality assessment tool for quantitative research and the AMSTAR-2 for systematic reviews.

RESULTS

The literature search identified 5385 unique studies; 38 were included in the review. We discovered 19 risk stratification tools, one of which was established in EMS patient care. One-third of risk stratification tools have been validated. Two main approaches for the application of the tools were identified. Elements of the tools were categorised in history taking, physical examination, electrocardiogram, additional examinations and other variables. Evaluation of measurement properties showed that negative and positive predictive value was used in half of the studies to assess the accuracy of tools.

CONCLUSION

A total of 19 risk stratification tools for syncope patients were identified. They were primarily established in ED patient care; most are not validated properly. Key elements in the risk stratification related to a potential cardiac problem as cause for the syncope. These insights provide directions for the key elements of a risk stratification tool and for a more advanced process to validate risk stratification tools.

Derivation and validation of a blood biomarker score for 2-day mortality prediction from prehospital care: a multicenter, cohort, EMS-based study

Identifying potentially life-threatening diseases is a key challenge for emergency medical services. This study aims at examining the role of different prehospital biomarkers from point-of-care testing to derive and validate a score to detect 2-day in-hospital mortality. We conducted a prospective, observational, prehospital, ongoing, and derivation-validation study in three Spanish provinces, in adults evacuated by ambulance and admitted to the emergency department. A total of 23 ambulance-based biomarkers were collected from each patient. A biomarker score based on logistic regression was fitted to predict 2-day mortality from an optimum subset of variables from prehospital blood analysis, obtained through an automated feature selection stage. 2806 cases were analyzed, with a median age of 68 (interquartile range 51-81), 42.3% of women, and a 2-day mortality rate of 5.5% (154 non-survivors). The blood biomarker score was constituted by the partial pressure of carbon dioxide, lactate, and creatinine. The score fitted with logistic regression using these biomarkers reached a high performance to predict 2-day mortality, with an AUC of 0.933 (95% CI 0.841-0.973). The following risk levels for 2-day mortality were identified from the score: low risk (score < 1), where only 8.2% of non-survivors were assigned to; medium risk (1 ≤ score < 4); and high risk (score ≥ 4), where the 2-day mortality rate was 57.6%. The novel blood biomarker score provides an excellent association with 2-day in-hospital mortality, as well as real-time feedback on the metabolic-respiratory patient status. Thus, this score can help in the decision-making process at critical moments in life-threatening situations.

Performance of a prehospital HEART score in patients with possible myocardial infarction: a prospective evaluation

INTRODUCTION

The History, Electrocardiogram (ECG), Age, Risk Factors and Troponin (HEART) score is commonly used to risk stratify patients with possible myocardial infarction as low risk or high risk in the Emergency Department (ED). Whether the HEART score can be used by paramedics to guide care were high-sensitivity cardiac troponin testing available in a prehospital setting is uncertain.

METHODS

In a prespecified secondary analysis of a prospective cohort study where paramedics enrolled patients with suspected myocardial infarction, a paramedic Heart, ECG, Age, Risk Factors (HEAR) score was recorded contemporaneously, and a prehospital blood sample was obtained for subsequent cardiac troponin testing. HEART and modified HEART scores were derived using laboratory contemporary and high-sensitivity cardiac troponin I assays. HEART and modified HEART scores of ≤3 and ≥7 were applied to define low-risk and high-risk patients, and performance was evaluated for an outcome of major adverse cardiac events (MACEs) at 30 days.

RESULTS

Between November 2014 and April 2018, 1054 patients were recruited, of whom 960 (mean 64 (SD 15) years, 42% women) were eligible for analysis and 255 (26%) experienced a MACE at 30 days. A HEART score of ≤3 identified 279 (29%) as low risk with a negative predictive value of 93.5% (95% CI 90.0% to 95.9%) for the contemporary assay and 91.4% (95% CI 87.5% to 94.2%) for the high-sensitivity assay. A modified HEART score of ≤3 using the limit of detection of the high-sensitivity assay identified 194 (20%) patients as low risk with a negative predictive value of 95.9% (95% CI 92.1% to 97.9%). A HEART score of ≥7 using either assay gave a lower positive predictive value than using the upper reference limit of either cardiac troponin assay alone.

CONCLUSIONS

A HEART score derived by paramedics in the prehospital setting, even when modified to harness the precision of a high-sensitivity assay, does not allow safe rule-out of myocardial infarction or enhanced rule-in compared with cardiac troponin testing alone.

Venous blood point-of-care testing (POCT) for paramedics in urgent and emergency care: protocol for a single-site feasibility study (POCTPara)

The COVID-19 pandemic placed the UK healthcare system under unprecedented pressure, and recovery will require whole-system investment in innovative, flexible and pragmatic solutions. Positioned at the heart of the healthcare system, ambulance services have been tasked with addressing avoidable hospital conveyance and reducing unnecessary emergency department and hospital attendances through the delivery of care closer to home. Having begun to implement models of care intended to increase 'see and treat' opportunities through greater numbers of senior clinical decision makers, emphasis has now been placed upon the use of remote clinical diagnostic tools and near-patient or point-of-care testing (POCT) to aid clinical decision making. In terms of POCT of blood samples obtained from patients in the pre-hospital setting, there is a paucity of evidence beyond its utility for measuring lactate and troponin in acute presentations such as sepsis, trauma and myocardial infarction, although potential exists for the analysis of a much wider panel of analytes beyond these isolated biomarkers. In addition, there is a relative dearth of evidence in respect of the practicalities of using POCT analysers in the pre-hospital setting. This single-site feasibility study aims to understand whether it is practical to use POCT for the analysis of patients' blood samples in the urgent and emergency care pre-hospital setting, through descriptive data of POCT application and through qualitative focus group interviews of advanced practitioners (specialist paramedics) to inform the feasibility and design of a larger study. The primary outcome measure is focus group data measuring the experiences and perceived self-reported impact by specialist paramedics. Secondary outcome measures are number and type of cartridges used, number of successful and unsuccessful attempts in using the POCT analyser, length of time on scene, specialist paramedic recruitment and retention, number of patients who receive POCT, descriptive data of safe conveyance, patient demographics and presentations where POCT is applied and data quality. The study results will inform the design of a main trial if indicated.

Establishment of a nomogram model for acute chest pain triage in the chest pain center

Background

Acute myocardial infarction (AMI) is the leading life-threatening disease in the emergency department (ED), so rapid chest pain triage is important. This study aimed to establish a clinical prediction model for the risk stratification of acute chest pain patients based on the Point-of-care (POC) cardiac troponin (cTn) level and other clinical variables.

Methods

We conducted a post-hoc analysis of the database from 6,019 consecutive patients (excluding prehospital-diagnosed non-cardiac chest pain patients) attending a local chest pain center (CPC) in China between October 2016 and January 2019. The plasma concentration of cardiac troponin I (cTnI) was measured using a POC cTnI (Cardio Triage, Alere) assay. All the eligible patients were randomly divided into training and validation cohorts by a 7:3 ratio. We performed multivariable logistic regression to select variables and build a nomogram based on the significant predictive factors. We evaluated the model's generalization ability of diagnostic accuracy in the validation cohort.

Results

We analyzed data from 5,397 patients that were included in this research. The median turnaround time (TAT) of POC cTnI was 16 min. The model was constructed with 6 variables: ECG ischemia, POC cTnI level, hypotension, chest pain symptom, Killip class, and sex. The area under the ROC curve (AUC) in the training and validation cohorts was 0.924 and 0.894, respectively. The diagnostic performance was superior to the GRACE score (AUC: 0.737).

Conclusion

A practical predictive model was created and could be used for rapid and effective triage of acute chest pain patients in the CPC.

Prehospital Comparison of the HEAR and HE-MACS Scores for 30-Day Adverse Cardiac Events

OBJECTIVE

The History, Electrocardiogram (ECG), Age, and Risk factor (HEAR) and History and ECG-only Manchester Acute Coronary Syndromes (HE-MACS) risk scores can risk stratify chest pain patients without troponin measures. The objective of this study was to determine if either risk score could achieve the ≥99% negative predictive value (NPV) required to rule out major adverse cardiovascular events (MACE; a composite of all-cause death, myocardial infarction, or coronary revascularization) at 30 days or the ≥50% positive predictive value (PPV) indicative of a patient possibly needing interventional cardiology.

METHODS

We performed a pre-planned secondary analysis of the prospective multisite PARAHEART (n = 462, 12/2016-1/2018) and RESCUE (n = 767, 4/2018-1/2019) trials, which accrued adults ≥21 years old with acute non-traumatic chest pain transported by emergency medical services (EMS). Paramedics prospectively completed risk assessment forms. Very low risk was defined by a HEAR score of 0-1 or HE-MACS probability <4%. The primary outcome was 30-day MACE, which was determined by adjudication (PARAHEART) or electronic record review (RESCUE). NPV and PPV with exact 95% confidence intervals (95%CI) for 30-day MACE were calculated for each risk score and compared using McNemar's tests.

RESULTS

Among the PARAHEART and RESCUE cohorts, 30-day MACE occurred in 18.8% (87/462) and 6.9% (53/767) of patients, respectively. In PARAHEART, 7.8% (36/462) were very low risk by HEAR score vs. 7.8% (36/462) by HE-MACS (p = 1.0). The HEAR score had a NPV of 97.2% (95%CI 91.9-100.0) vs. 91.7% (95%CI 82.6-100.0) for HE-MACS (p = 0.15). The HEAR and HE-MACS PPVs were similar [46.4% (95%CI 28.0-64.9) vs. 33.3% (95%CI 13.2-53.5) (p = 0.26)]. In RESCUE, the HEAR score identified 14.2% (109/767) as low risk compared to 8.3% (64/767) by HE-MACS (p < 0.001). In this cohort, the HEAR and HE-MACS scores had similar NPVs [98.2% (95%CI 95.7-100.0) vs. 98.4% (95%CI 95.4-100.0) (p = 0.89)] and PPVs [16.2% (95%CI 6.2-32.0) vs. 22.6% (95%CI 12.3-36.2) (p = 0.41)].

CONCLUSIONS

In two prehospital chest pain cohorts, neither the HEAR score nor HE-MACS achieved sufficient NPV or PPV to rule out or rule in 30-day MACE.

Integrating Microfluidics and Electronics in Point-of-Care Diagnostics: Current and Future Challenges

Point-of-Care (POC) diagnostics have gained increasing attention in recent years due to its numerous advantages over conventional diagnostic approaches. As proven during the recent COVID-19 pandemic, the rapidity and portability of POC testing improves the efficiency of healthcare services and reduces the burden on healthcare providers. There are hundreds of thousands of different applications for POC diagnostics, however, the ultimate requirement for the test is the same: sample-in and result-out. Many technologies have been implemented, such as microfluidics, semiconductors, and nanostructure, to achieve this end. The development of even more powerful POC systems was also enabled by merging multiple technologies into the same system. One successful example is the integration of microfluidics and electronics in POC diagnostics, which has simplified the sample handling process, reduced sample usage, and reduced the cost of the test. This review will analyze the current development of the POC diagnostic systems with the integration of microfluidics and electronics and discuss the future challenges and perspectives that researchers might have.

A review of temperature-related challenges and solutions for the Abbott i-STAT and Siemens Healthineers epoc devices

The Abbott i-STAT and Siemens Healthineers epoc are commonly used in the provision of care during emergency medical services calls and other settings. Maintaining these systems within manufacturer's temperature claims in these settings poses challenges across the world. This review summarizes solutions that have been reported in the peer-reviewed literature and proposes additional strategies to further address these challenges. A literature search was performed with Clarivate's Web of Science from inception to August 3, 2022. Search terms included i-STAT, epoc, temperature, cold, hot, heat, freeze, frozen, prehospital, disaster, POCT, point of care, blood gas, helicopter, airplane, and ambulance. One author also reviewed manually every issue of the Journal of Paramedic Practice. The search identified 17 solutions for addressing temperature-related challenges with the i-STAT device, nine solutions for i-STAT cartridges, one solution for the epoc device, and one solution for the epoc test card. The majority of solutions were highly portable and consisted of widely available, inexpensive components. The solutions demonstrated only partial or entirely questionable effectiveness in achieving temperature control. The search also identified five reports on the impact of storage temperatures on cartridges and test cards. The reports suggested that these reagents may be able to withstand storage at temperatures outside of manufacturer's claims with only minimal deterioration in performance. The heterogeneity of solutions and the paucity of evidence on their effectiveness suggest that additional strategies are needed to better understand and further address temperature-related challenges with these systems. A collaborative approach and shared decision making are recommended.

Early risk assessment in patients with suspected NSTE-ACS; a retrospective cohort study

INTRODUCTION

Chest pain is among the most common reasons for Emergency Department (ED) presentation, while most patients should be considered low risk for Acute Coronary Syndrome (ACS). Management of these patients places a significant burden on our health care system. Various risk scores have been developed to facilitate the triage of patients with chest pain. However, it remains unclear which score performs best in identifying low risk patients, in various settings. The aim of this study was to determine which risk score performs best in ruling out non-ST elevation ACS (NSTE-ACS).

METHODS

Data was collected from all patients >18 years presenting to the ED between 01 and 01-2019 and 01-07-2019, if they were suspected of NSTE-ACS. Primary endpoint was NSTE-ACS during presentation to the ED or hospitalization, according to the 2020 ESC guidelines. In a secondary analysis we determined the number low-risk patients, at set safety levels of 95% and 98%.

RESULTS

A total of 536 patients were included, 192 (35.9%) were admitted to the hospital and NSTE-ACS occurred in 134 of 536 patients (25.0%). When areas under the curve (AUC) were compared, pre-HEART (0.869; CI 0.835-0.903), T-MACS (0.862; CI 0.825-0.898) and HEART (0.850; CI 0.815-0.885) performed best. At a safety level of 98%, the HEART score was the best performing risk score and identified 28.9% of patients as low risk, and missed 0 cases of NSTE-ACS. Followed by the pre-HEART score, which identified 18.3% of all patients as low risk, and missed 0% of NSTE-ACS.

CONCLUSIONS

The newly developed pre-HEART score is both practical and has accurate diagnostic properties, closely followed by the HEART score, and T-MACS. New pre-hospital risk scores are promising and much needed. Future studies should focus on the usage of pre-hospital scores for triage of patients with chest pain, in order to reduce the burden on emergency health care.

Outcomes of ambulance arrival vs. self-presentation in acute heart failure: an insight from the heart failure registry in Pakistan

OBJECTIVES

We aimed to demonstrate the outcomes of various presentations of acute heart failure (AHF), as well as test the generalizability of previous results in routine clinical practice.

METHODS

This retrospective cohort study compares two patient groups of AHF: those who self-presented compared to those who used an ambulance. The primary endpoint was the measure of 30-, 180-, and 365-day cardiovascular (CV) mortality after the index hospitalization event. Secondary endpoints included HF rehospitalization within 30 days of enrollment, index hospital stay, and death from any cause during the index hospitalization. The relationship between the two modes of presentation was calculated by multivariate analysis.

RESULTS

A total of 14,454 patients with AHF presented to the emergency department. Patients who presented by ambulance had a higher 30-, 180-, and 365-day mortality than those who self-presented (30-day: 5.57% vs. 3.53%, OR [95% CI]: 0.65 [0.24-0.93], p-value <0.001; 180-day: 11.25% vs. 8.41%, OR [95% CI]: 0.52 [0.34-0.97], p-value = 0.021; and 365-day: 19.25% vs. 15.48%, OR [95% CI]: 0.67 [0.33-0.95], p-value <0.001).

CONCLUSION

AHF patients who presented via ambulance had a higher 30-, 180-, and 365-day mortality as compared to self-presentation.

Prehospital time for patients with acute cardiac complaints: A rural health disparity

OBJECTIVE

Delays in care for patients with acute cardiac complaints are associated with increased morbidity and mortality. The objective of this study was to quantify rural and urban differences in prehospital time intervals for patients with cardiac complaints.

METHODS

The ESO Data Collaborative dataset consisting of records from 1332 EMS agencies was queried for 9-1-1 encounters with acute cardiac problems among adults (age ≥ 18) from 1/1/2013-6/1/2018. Location was classified as rural or urban using the 2010 United States Census. The primary outcome was total prehospital time. Generalized estimating equations evaluated differences in the average times between rural and urban encounters while controlling for age, sex, race, transport mode, loaded mileage, and patient stability.

RESULTS

Among 428,054 encounters, the median age was 62 (IQR 50-75) years with 50.7% female, 75.3% white, and 10.3% rural. The median total prehospital, response, scene, and transport times were 37.0 (IQR 29.0-48.0), 6.0 (IQR 4.0-9.0), 16.0 (IQR 12.0-21.0), and 13.0 (IQR 8.0-21.0) minutes. Rural patients had an average total prehospital time that was 16.76 min (95%CI 15.15-18.38) longer than urban patients. After adjusting for covariates, average total time was 5.08 (95%CI 4.37-5.78) minutes longer for rural patients. Average response and transport time were 4.36 (95%CI 3.83-4.89) and 0.62 (95%CI 0.33-0.90) minutes longer for rural patients. Scene time was similar in rural and urban patients (0.09 min, 95%CI -0.15-0.33).

CONCLUSION

Rural patients with acute cardiac complaints experienced longer prehospital time than urban patients, even after accounting for other key variables, such as loaded mileage.

Point-of-care testing with high-sensitivity cardiac troponin assays: the challenges and opportunities

Methods to improve the safety, accuracy and efficiency of assessment of patients with suspected acute coronary symptoms have occupied decades of study and have supported significant changes in clinical practice. Much of the progress is reliant on results of laboratory-based high-sensitivity cardiac troponin assays that can detect low concentrations with high precision. Until recently, point-of-care (POC) platforms were unable to perform with similar analytical precision as laboratory-based assays, and recommendations for their use in accelerated assessment strategies for patients with suspected acute coronary syndrome has been limited. As POC assays can provide troponin results within 20 min, and can be used proximate to patient care, improvements in the efficiency of assessment of patients with suspected acute coronary syndrome is possible, particularly with new high-sensitivity assays.

Prehospital troponin as a predictor of early clinical deterioration

BACKGROUND AND OBJECTIVES

Elevated troponin T (cTnT) values are associated with comorbidities and early mortality, in both cardiovascular and noncardiovascular diseases. The objective of this study is to evaluate the prognostic accuracy of the sole utilization of prehospital point-of-care cardiac troponin T to identify the risk of early in-hospital deterioration, including mortality within 28 days.

METHODS

We conducted a prospective, multicentric, controlled, ambulance-based, observational study in adults with acute diseases transferred with high priority by ambulance to emergency departments, between 1 January and 30 September 2020. Patients with hospital diagnosis of acute coronary syndrome were excluded. The discriminative power of the predictive cTnT was assessed through a discrimination model trained using a derivation cohort and evaluated by the area under the curve of the receiver operating characteristic on a validation cohort.

RESULTS

A total of 848 patients were included in our study. The median age was 68 years (25th-75th percentiles: 50-81 years), and 385 (45.4%) were women. The mortality rate within 28 days was 12.4% (156 cases). The predictive ability of cTnT to predict mortality presented an area under the curve of 0.903 (95% CI: 0.85-0.954; P < .001). Risk stratification was performed, resulting in three categories with the following optimal cTnT cut-off points: high risk greater than or equal to 100, intermediate risk 40-100 and low risk less than 40 ng/L. In the high-risk group, the mortality rate was 61.7%, and on the contrary, the low-risk group presented a mortality of 2.3%.

CONCLUSIONS

The implementation of a routine determination of cTnT on the ambulance in patients transferred with high priority to the emergency department can help to stratify the risk of these patients and to detect unknown early clinical deterioration.

Experimental Technologies in the Diagnosis and Treatment of COVID-19 in Patients with Comorbidities

The COVID-19 pandemic has impacted the whole world and raised concerns about its effects on different human organ systems. Early detection of COVID-19 may significantly increase the rate of survival; thus, it is critical that the disease is detected early. Emerging technologies have been used to prevent, diagnose, and manage COVID-19 among the populace in the USA and globally. Numerous studies have revealed the growing implementation of novel engineered systems during the intervention at various points of the disease’s pathogenesis, especially as it relates to comorbidities and complications related to cardiovascular and respiratory organ systems. In this review, we provide a succinct, but extensive, review of the pathogenesis of COVID-19, particularly as it relates to angiotensin-converting enzyme 2 (ACE2) as a viral entry point. This is followed by a comprehensive analysis of cardiovascular and respiratory comorbidities of COVID-19 and novel technologies that are used to diagnose and manage hospitalized patients. Continuous cardiorespiratory monitoring systems, novel machine learning algorithms for rapidly triaging patients, various imaging modalities, wearable immunosensors, hotspot tracking systems, and other emerging technologies are reviewed. COVID-19 effects on the immune system, associated inflammatory biomarkers, and innovative therapies are also assessed. Finally, with emphasis on the impact of wearable and non-wearable systems, this review highlights future technologies that could help diagnose, monitor, and mitigate disease progression. Technologies that account for an individual’s health conditions, comorbidities, and even socioeconomic factors can drastically reduce the high mortality seen among many COVID-19 patients, primarily via disease prevention, early detection, and pertinent management.

The Ambulance Cardiac Chest Pain Evaluation in Scotland Study (ACCESS): A Prospective Cohort Study

STUDY OBJECTIVE

To determine whether risk stratification in the out-of-hospital setting could identify patients with chest pain who are at low and high risk to avoid admission or aid direct transfer to cardiac centers.

METHODS

Paramedics prospectively enrolled patients with suspected acute coronary syndrome without diagnostic ST-segment elevation on the ECG. The History, ECG, Age and Risk Factors (HEAR) score was recorded contemporaneously, and out-of-hospital samples were obtained to measure cardiac Troponin I (cTnI) level on a point-of-care device, to allow calculation of the History, ECG, Age, Risk Factors, and Troponin (HEART) score. HEAR and HEART scores less than or equal to 3 and greater than or equal to 7 were defined as low and high risk for major adverse cardiac events at 30 days.

RESULTS

Of 1,054 patients (64 years [SD 15 years]; 42% women), 284 (27%) experienced a major adverse cardiac event at 30 days. The HEAR score was calculated in all patients, with point-of-care cTnI testing available in 357 (34%). A HEAR score less than or equal to 3 identified 32% of patients (334/1,054) as low risk, with a sensitivity of 84.9% (95% confidence interval [CI] 80.7% to 89%), whereas a score greater than or equal to 7 identified just 3% of patients (30/1,054) as high risk, with a specificity of 98.7% (95% CI 97.9% to 99.5%). A point-of-care HEART score less than or equal to 3 identified a similar proportion as low risk (30%), with a sensitivity of 87.0% (95% CI 80.7% to 93.4%), whereas a score greater than or equal to 7 identified 14% as high risk, with a specificity of 94.8% (95% CI 92.0% to 97.5%).

CONCLUSION

Paramedics can use the HEAR score to discriminate risk, but even when used in combination with out-of-hospital point-of-care cTnI testing, the HEART score does not safely rule out major adverse cardiac events, and only a small proportion of patients are identified as high risk.

Comparison of a single high-sensitivity cardiac troponin T measurement with the HEART score for rapid rule-out of acute myocardial infarction in a primary care emergency setting: a cohort study

OBJECTIVE

This study aims to compare the rule-out safety of a single high-sensitivity cardiac troponin T (hs-cTnT) with the History, ECG, Age, Risk factors and Troponin (HEART) score in a low-prevalence primary care setting of acute myocardial infarction (AMI).

PARTICIPANTS

Patients with non-specific symptoms suggestive of AMI were consecutively enroled at a primary care emergency clinic in Oslo, Norway from November 2016 to October 2018.

METHODS

After initial assessment by a general practitioner, hs-cTnT samples were drawn. AMI was ruled-out by a single hs-cTnT <5 ng/L measured ≥3 hours after symptom onset. The HEART score was calculated retrospectively; a score ≤3 of 10 points was considered low risk. We also calculated a modified HEART score using more sensitive hs-cTnT thresholds. The primary outcome was the diagnostic performance for the rule-out of AMI at the index event; the secondary the composite of AMI or all-cause death at 90 days.

RESULTS

Among 1711 patients, 61 (3.6%) were diagnosed with AMI, and 569 (33.3%) patients were assigned to single rule-out (<5 ng/L). With no AMIs in this group, the negative predictive value (NPV) and sensitivity were both 100.0% (95% CI 99.4% to 100.0% and 94.1% to 100.0%, respectively), and the specificity 34.5% (32.2% to 36.8%). The original HEART score triaged more patients as low risk (n=871), but missed five AMIs (NPV 99.4% (98.7% to 99.8%); sensitivity 91.8% (81.9% to 97.3%) and specificity 52.5% (50.0% to 54.9%)). The modified HEART score increased the low-risk sensitivity to 98.4% (91.2% to 100.0%), with specificity 38.7% (36.3% to 41.1%). The 90-day incidence of AMI or death in the single rule-out and the original and modified low-risk HEART groups were 0.0%, 0.7%, and 0.2%, respectively.

CONCLUSION

In a primary care emergency setting, a single hs-cTnT strategy was superior to the HEART score in ruling out AMI. This rapid and safe approach may enhance the assessment of patients with chest pain outside of hospitals.

TRIAL REGISTRATION NUMBER

NCT02983123.

Point-of-Care Testing Practices, Failure Modes, and Risk-Mitigation Strategies in Emergency Medical Services Programs in the Canadian Province of Alberta

CONTEXT.—

Emergency medical services (EMS) programs have been using point-of-care testing (POCT) for more than 20 years. However, only a handful of reports have been published in all of that time on POCT practices in field settings.

OBJECTIVE.—

To provide an overview of POCT practices and failure modes in 3 of Alberta's EMS programs, and to propose risk-mitigation strategies for reducing or eliminating these failure modes.

DESIGN.—

Details about POCT practices, failure modes, and risk-mitigation strategies were gathered through (1) conversations with personnel, (2) in-person tours of EMS bases, (3) accompaniment of EMS personnel on missions, (4) internet searches for publicly available information, and (5) a review of laboratory documents.

RESULTS.—

Practices were most standardized and robust in the community paramedicine program (single service provider, full laboratory oversight), and least standardized and robust in the air ambulance program (4 service providers, limited laboratory oversight). Common failure modes across all 3 programs included device inoperability due to cold weather, analytical validation procedures that failed to consider the unique challenges of EMS settings, and a lack of real-time electronic transmission of results into the health care record.

CONCLUSIONS.—

A provincial framework for POCT in EMS programs is desirable. Such a framework should include appropriate funding models, laboratory oversight of POCT, and relevant expertise on POCT in EMS settings. The framework should also incorporate specific guidance on quality standards that are needed to address the unique challenges of performing POCT in field settings.

Pre-hospital One-Hour Troponin in a Low-Prevalence Population of Acute Coronary Syndrome: OUT-ACS study

Objective

The European Society of Cardiology 0/1-hour algorithm for high-sensitivity cardiac troponin T (hs-cTnT) has demonstrated high rule-out safety in large hospital validation cohorts. We aimed to validate the algorithm in a primary care setting, where patients have a lower pretest probability for acute coronary syndrome.

Methods

This prospective, observational, diagnostic study included patients with acute non-specific chest pain admitted to a primary care emergency clinic in Oslo, Norway, from November 2016 to October 2018. hs-cTnT was measured after 0, 1 and 4 hours. The primary outcome measure was the diagnostic performance of the 0/1-hour algorithm, the 90-day incidence of AMI or all-cause death the secondary.

Results

Among 1711 included patients, 61 (3.6%) were diagnosed with AMI. By applying the algorithm, 1311 (76.6%) patients were assigned to the rule-out group. The negative predictive value was 99.9% (95% CI 99.5% to 100.0%), the sensitivity and specificity 98.4% (91.2–100.0) and 79.4% (77.4–81.3), respectively. Sixty-six (3.9%) patients were triaged towards rule-in, where 45 were diagnosed with AMI. The corresponding positive predictive value was 68.2% (58.3–76.7), sensitivity 73.8% (60.9–84.2), and specificity 98.7% (98.1–99.2). Among 334 (19.5%) patients assigned to the observation group in need of further tests, 15 patients had an AMI. The following 90 days, five new patients experienced an AMI and nine patients died, with a low incidence in the rule-out group (0.3%).

Conclusion

The 0/1-hour algorithm for hs-cTnT seems safe, efficient and applicable for an accelerated assessment of patients with non-specific chest pain in a primary care emergency setting.

Trial registration number

NCT02983123.

Diagnostic Performance of Prehospital Point-of-Care Troponin Tests to Rule Out Acute Myocardial Infarction: A Systematic Review

INTRODUCTION

Chest pain is one of the most common reasons for 999 calls and transfers to the emergency department (ED). In these patients, acute myocardial infarction (AMI) is often the diagnosis that clinicians are seeking to exclude. However, only a minority of those patients have AMI, causing a substantial financial burden to health services. Cardiac troponin (cTn) is the reference standard biomarker for the diagnosis of AMI. Several commercially available point-of-care (POC) cTn assays are portable and could feasibly be used in an ambulance. The aim of this paper is to systematically review existing evidence for the use of POC cTn assays in the prehospital setting to rule out AMI.

METHODS

A systematic search was conducted on EMBASE, MEDLINE, and CINAHL Plus databases, reference lists, and relevant grey literature, including combinations of the relevant terms. Papers published in English language since the year 2000 were eligible for inclusion. A narrative synthesis of the evidence was then undertaken.

RESULTS

The initial search and cross-referencing revealed a total of 350 papers, of which 243 were excluded. Seven papers were included in the systematic literature review.

CONCLUSION

Current evidence does not support the use of POC troponin assays to exclude AMI due to issues with diagnostic accuracy and insufficient high-quality evidence.