Clinical performance of a new point-of-care cardiac troponin I assay compared to three laboratory troponin assays

Barbed arrow-like structure membrane with ultra-high rectification coefficient enables ultra-fast, highly-sensitive lateral-flow assay of cTnI

Acute myocardial infarction (AMI) has become a public health disease threatening public life safety due to its high mortality. The lateral-flow assay (LFA) of a typical cardiac biomarker, troponin I (cTnI), is essential for the timely warnings of AMI. However, it is a challenge to achieve an ultra-fast and highly-sensitive assay for cTnI (hs-cTnI) using current LFA, due to the limited performance of chromatographic membranes. Here, we propose a barbed arrow-like structure membrane (BAS Mem), which enables the unidirectional, fast flow and low-residual of liquid. The liquid is rectified through the forces generated by the sidewalls of the barbed arrow-like grooves. The rectification coefficient of liquid flow on BAS Mem is 14.5 (highest to date). Using BAS Mem to replace the conventional chromatographic membrane, we prepare batches of lateral-flow strips and achieve LFA of cTnI within 240 s, with a limit of detection of 1.97 ng mL-1. The lateral-flow strips exhibit a specificity of 100%, a sensitivity of 93.3% in detecting 25 samples of suspected AMI patients. The lateral-flow strips show great performance in providing reliable results for clinical diagnosis, with the potential to provide early warnings for AMI.

Rule-out of non-ST elevation myocardial infarction by five point of care cardiac troponin assays according to the 0 h/3 h algorithm of the European Society of Cardiology

Background:

Point of care (POC) assays for cardiac troponins I or T (cTnI or cTnT) may accelerate the diagnosis of patients with suspected acute coronary syndrome (ACS). However, their clinical utility according to the 0 h/3 h algorithm recommended by the European Society of Cardiology (ESC) for non-ST elevation myocardial infarction (NSTEMI) is unknown.

Methods:

Blood samples from 90 patients with suspected ACS were obtained at hospital admission and 3 h later. Concentrations of cTn were determined using five POC assays (AQT90 FLEX cTnI and cTnT; PATHFAST™ cTnI; Stratus CS 200 cTnI; and Triage MeterPro cTnI) and two guideline-acceptable high-sensitivity (hs) immunoassays.

Results:

For the diagnosis of NSTEMI (n=15), AUCs for Abbott hs-cTnI and Roche hs-cTnT were 0.86 [95% confidence interval (CI), 0.75–0.96] and 0.88 (95% CI, 0.80–0.95), respectively, at admission, and 0.96 and 0.94, respectively, 3 h later. With the 99th percentile cutoff, their sensitivities were 62% and 92%, respectively, at admission, and 77% and 100%, respectively, 3 h later. The PATHFAST™ cTnI assay showed AUCs of 0.90 (95% CI, 0.82–0.97) and 0.94 (95% CI, 0.89–1.00), respectively, and sensitivities of 67% and 75% at admission and 3 h later, respectively. The other cTn POC assays had AUCs of 0.71 (95% CI, 0.53–0.89) to 0.84 (95% CI, 0.71–0.96) and 0.86 (95% CI, 0.72–0.99) to 0.87 (95% CI, 0.75–0.99) and sensitivities of 39%–50% and 62%–77% at admission and 3 h later, respectively.

Conclusions:

PATHFAST™ cTnI assay proved itself as comparable to ESC-guideline acceptable hs-cTn assays. The lower sensitivity of the other POC assays limits their clinical utility and would require longer follow-up monitoring of patients for the safe NSTEMI rule-out.

Diagnostic performance of point-of-care and central laboratory cardiac troponin assays in an emergency department

Early diagnosis of myocardial infarction (MI) with cardiac troponin (cTn) assays at the point-of-care (POC) is suggested to shorten turn-around-time in the emergency department (ED). The present study aimed at comparing the diagnostic performance of two POC cTn assays with that of a central laboratory high-sensitivity (hs) method, under routine ED conditions. In 2,163 non-selected ED patients suspected for MI, the diagnostic performance of the POC troponin I (TnI), troponin T (TnT), and hs-TnT assay for the prediction of MI was evaluated based on receiver operating characteristic (ROC) analyses and compared with the performance based on the manufacturers' cut-offs. Due to an observed association between renal function as determined by estimated glomerular filtration rate (eGFR) and cTn concentrations, all analyses were stratified by renal function. In patients with normal renal function (eGFR > 60 mL/min/1.73m2), POC and hs assays showed a comparable diagnostic performance as quantified by the area under the ROC curve (AUC) of about 0.88. The ROC-derived optimal cut-off (OCO) levels for the different cTn assays clearly changed with decreasing kidney function. Impaired kidney function required OCO to be three to five times higher to achieve a comparable performance. Particularly cTnT concentrations were strongly associated with renal function. The three cTn assays demonstrated equivalent diagnostic performance in ED-patients admitted with suspected ACS in relation to the release diagnosis, supporting the use of POC testing in this setting. The present results implicate that application of eGFR-specific OCOs may decrease false-positives among patients with impaired renal function. Providing individual cut-offs depending on patients' eGFR might be an appropriate add-on tool to improve specificity in the diagnosis of MI.

High-sensitivity detection of cardiac troponin I with UV LED excitation for use in point-of-care immunoassay

High-sensitivity cardiac troponin assay development enables determination of biological variation in healthy populations, more accurate interpretation of clinical results and points towards earlier diagnosis and rule-out of acute myocardial infarction. In this paper, we report on preliminary tests of an immunoassay analyzer employing an optimized LED excitation to measure on a standard troponin I and a novel research high-sensitivity troponin I assay. The limit of detection is improved by factor of 5 for standard troponin I and by factor of 3 for a research high-sensitivity troponin I assay, compared to the flash lamp excitation. The obtained limit of detection was 0.22 ng/L measured on plasma with the research high-sensitivity troponin I assay and 1.9 ng/L measured on tris-saline-azide buffer containing bovine serum albumin with the standard troponin I assay. We discuss the optimization of time-resolved detection of lanthanide fluorescence based on the time constants of the system and analyze the background and noise sources in a heterogeneous fluoroimmunoassay. We determine the limiting factors and their impact on the measurement performance. The suggested model can be generally applied to fluoroimmunoassays employing the dry-cup concept.

A systematic evaluation of immunoassay point-of-care testing to define impact on patients' outcomes

Background Point-of-care testing has been developed to provide rapid test results. Most published studies focus on analytical performance, neglecting its impact on patient outcomes. Objective To review the analytical performance and accuracy of point-of-care testing specifically planned for immunoassay and to evaluate the impact of faster results on patient management. Methods A search of electronic databases for studies reporting immunoassay results obtained in both point-of-care testing and central laboratory scenarios was performed. Data were extracted concerning the study details, and the methodological quality was assessed. The analytical characteristics and diagnostic accuracy of six points-of-care testing: troponin, procalcitonin, parathyroid hormone, brain natriuretic peptide, C-reactive protein and neutrophil gelatinase-associated lipocalin were evaluated. Results A total of 116 scientific papers were analysed. Studies measuring procalcitonin, parathyroid hormone and neutrophil gelatinase-associated lipocalin reported a limited impact on diagnostic decisions. Seven studies measuring C-reactive protein claimed a significant reduction of antibiotic prescription. Several authors evaluated brain natriuretic peptide or troponin reporting faster decision-making without any improvement in clinical outcome. Forty-four per cent of studies reported analytical data, showing satisfactory correlations between results obtained through point-of-care testing and central laboratory setting. Half of studies defined the diagnostic accuracy of point-of-care testing as acceptable for troponin (median sensitivity and specificity: 74% and 94%, respectively), brain natriuretic peptide (median sensitivity and specificity: 82% and 88%, respectively) and C-reactive protein (median sensitivity and specificity 85%). Conclusions Point-of-care testing immunoassay results seem to be reliable and accurate for troponin, brain natriuretic peptide and C-reactive protein. The satisfactory analytical performance, together with an excellent practicability, suggests that it could be a consistent tool in clinical practice, but data are lacking regarding the patient outcomes.

Clinical performance of cardiac Troponin I: A comparison between the POCT AQT90 FLEX and the Dimension Vista analyzer in an emergency setting

BACKGROUND

Cardiac troponin [cTn (I or T)] is the preferred biomarker for the diagnosis of myocardial infarction (MI).

AIM

We studied the analytical performance of the POCT AQT90 FLEX cTnI assay and its diagnostic accuracy, in comparison to the Dimension Vista cTnI method, in patients presenting to the Emergency Department (ED) with suspect of acute coronary syndrome (ACS).

METHODS

786 consecutive patients were enrolled. cTnI was measured at admission to the ED and about 3 and 6 hours later. The imprecision study was carried out using different lots of quality controls (QCs). ROC curve analysis was conducted using discharge diagnoses in order to verify the global diagnostic accuracy.

RESULTS

The concentrations measured in the QCs ranging from 0.033 to 1.26μg/L show CVs% ranging from 2.81 to 7.56%, comparable to those declared by the manufacturer. Passing-Bablok and linear regression analysis show a high significant correlation (R²=0.90, p<0.0001); Bland-Altman test describes a statistically significant negative bias (Bias=-0.2336; 95%CI=-0.4217/-0.0456, p=0.0150). ROC curves obtained using Dimension Vista and AQT90 FLEX cTnI assays displayed similar clinical performance being not statistically significant the difference of the corresponding AUC. Comparing sensitivity and specificity of cTnI concentrations obtained from the ROC curve analysis using AQT90 FLEX, we found a "best cut-off" (0.014μg/L) lower than that declared from the manufacturer (0.023μg/L).

CONCLUSIONS

The comparison of two different assays of cTnI against a diagnosis of acute MI (AMI) shows that both assays behave equally well with a high degree of sensitivity and specificity. The resulting "best cut-off" suggests that this AQT90 FLEX cTnI concentration could be evaluated as the potentially new "clinically usable" cut-off for AMI/myocardial necrosis diagnoses.

Three-month outcome of patients with suspected acute coronary syndrome using point-of-care cardiac troponin-T testing compared with laboratory-based cardiac troponin-T testing: a randomised trial

OBJECTIVE

The aim of this randomised trial was to determine clinical outcomes in patients suspected of an acute coronary syndrome (ACS) who had cardiac troponin-T measured by point-of-care (POC) compared with laboratory-based cardiac troponin-T testing. A secondary aim was to describe the correlation between the two troponin assays.

METHODS

Adults suspected of ACS were allocated to have troponin processed by POC or laboratory analyser. The primary outcome was a composite of acute myocardial infarction, coronary revascularisation, cardiac arrest and mortality at 3 months. Paired troponins taken on participants allocated to POC were used to determine correlation between troponin values obtained from laboratory and POC analysers.

RESULTS

There were 452 participants. 30 (13.1%) of 229 participants allocated to POC had at least one primary outcome event compared with 29 (13.0%) of 223 allocated to laboratory testing, a difference of 0.1% (95% CI -6.2% to 6.4%, p=0.98). Of 215 available paired troponins results, both analysers gave congruent results in 196 (91%) cases. The POC troponin was negative when the laboratory sample was positive in 16 (7%) cases. The POC troponin was positive when the laboratory sample was negative in 3 (1%) samples. Passing-Bablok regression analysis demonstrated both a constant and proportional difference between the two analytic methods.

CONCLUSIONS

Among patients suspected of an ACS, we found no evidence for a difference in adverse outcome when POC troponin was used in comparison with laboratory troponin. Due to the small sample size, an absolute difference of up to 6% in adverse outcome is possible.

TRIAL REGISTRATION NUMBER

ANZCTR#12612000319875.

Point-of-care testing: where is the evidence? A systematic survey

Point-of-care testing (POCT) has had rapid technological development and their use is widespread in clinical laboratories to assure reduction of turn-around-time and rapid patient management in some clinical settings where it is important to make quick decisions. Until now the papers published about the POCT have focused on the reliability of the technology used and their analytical accuracy. We aim to perform a systematic survey of the evidence of POCT efficacy focused on clinical outcomes, selecting POCT denoted special analytes characterized by possible high clinical impact. We searched in Medline and Embase. Two independent reviewers assessed the eligibility, extracted study details and assessed the methodological quality of studies. We analyzed 84 studies for five POCT instruments: neonatal bilirubin, procalcitonin, intra-operative parathyroid hormone, troponin and blood gas analysis. Studies were at high risk of bias. Most of the papers (50%) were studies of correlation between the results obtained by using POCT instruments and those obtained by using laboratory instruments. These data showed a satisfactory correlation between methods when similar analytical reactions were used. Only 13% of the studies evaluated the impact of POCT on clinical practice. POCT decreases the time elapsed for making decisions on patient management but the clinical outcomes have never been adequately evaluated. Our work shows that, although POCT has the potential to provide beneficial patient outcome, further studies may be required, especially for defining its real utility on clinical decision making.

Diagnostic performance of four point of care cardiac troponin I assays to rule in and rule out acute myocardial infarction

OBJECTIVE

This study evaluated the diagnostic performance of four point-of-care (POC) cardiac troponin I (cTnI) assays compared to a central laboratory cTnI assay for detecting myocardial injury and diagnosing acute myocardial infarction (AMI).

DESIGN AND METHODS

Plasma obtained at admission, 3 h, and 6 h post-admission in 169 patients presenting with symptoms suggestive of acute coronary syndrome (ACS) was studied. cTnI concentrations were measured on the Instrumentation Laboratory prototype GEM Immuno, Radiometer AQT90, Mitsubishi PATHFAST, Abbott i-STAT and the Ortho-Clinical Diagnostic Vitros assays. MI was determined based on 99th percentiles according to Universal MI guidelines.

RESULTS

For ruling in MI at presentation (0 h), the GEM Immuno (sensitivity 63%, specificity 85%) and PATHFAST (sensitivity 53%, specificity 86%) were comparable to the OCD (sensitivity 68%, specificity 81%), and significantly better (p<0.05) than the AQT90 (sensitivity 26%, specificity 93%) and i-STAT (sensitivity 32%, specificity 92%). cTnI concentrations and serial rising patterns after MI differed by each assay. Negative predictive values were >90% and ROC AUCs were >0.90 after 6h for all assays. Detection of myocardial injury in non-ischemic pathologies accounted for lower than 100% specificity for MI.

CONCLUSION

cTnI is a sensitive biomarker for detection of myocardial injury. The analytical variability that exists between POC cTnI assays demonstrates substantial diagnostic differences for ruling in and ruling out MI in patients presenting with symptoms suggestive of ACS.

Diagnostic accuracy of a point-of-care troponin I assay for acute myocardial infarction within 3 hours after presentation in early presenters to the emergency department with chest pain

BACKGROUND

Guidelines recommend that serial cardiac marker testing to rule out acute myocardial infarction (AMI) be performed for 8 to 12 hours after symptom onset. We aim to determine the diagnostic accuracy of a contemporary point-of-care (POC) troponin I (TnI) assay within 3 hours for patients presenting within 8 hours of symptom onset.

METHODS

The MIDAS study collected blood from patients presenting with suspected acute coronary syndrome at presentation and at 90 minutes, 3 hours, and 6 hours in whom the emergency physician planned an objective cardiac ischemia evaluation. Criterion standard diagnoses were adjudicated by experienced clinicians using all available medical records per American Heart Association/American College of Cardiology criteria. Reviewers were blinded to the investigational marker, Cardio3 TnI POC. The Cardio3 TnI reference value was defined as >0.05 ng/mL. Measures of diagnostic accuracy are presented with 95% CI.

RESULTS

A total of 858 of 1107 patients met the inclusion criteria. The study cohort had 476 men (55.5%) with median age of 57.0 years (interquartile range 48.0-67.0 years). Median time from symptom onset to initial blood draw was 3.9 hours (interquartile range 2.7-5.2 hours). Acute myocardial infarction was diagnosed in 82 patients (9.6%). The sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio over 3 hours were 84.1, 93.4, 12.8, and 0.17, respectively. There was no significant improvement in diagnostic accuracy associated with adding 6-hour serial testing to the 3-hour sample.

CONCLUSION

In suspected patients with acute coronary syndrome presenting to the emergency department within 8 hours of symptom onset, 3 hours of serial testing with the Cardio3 TnI POC platform provides similar diagnostic accuracy for AMI as longer periods.

Point of care technology or standard laboratory service in an emergency department: is there a difference in time to action? A randomised trial

Background

Emergency Departments (ED) have a high flow of patients and time is often crucial. New technologies for laboratory analysis have been developed, including Point of Care Technologies (POCT), which can reduce the transport time and time of analysis significantly compared with central laboratory services. However, the question is if the time to clinical action is also reduced if a decisive laboratory answer is available during the first contact between the patient and doctor. The present study addresses this question: Does a laboratory answer, provided by POCT to the doctor who first attends the patient on admission, change the time to clinical decision in commonly occurring diseases in an ED compared with the traditional service from a central laboratory?

Methods

We performed a randomised clinical trial with parallel design and allocation ratio 1:1. The eligibility Criteria were: All patients referred from General Practitioner or another referring doctor suspected for a deep venous thrombosis (DVT), acute coronary syndrome (ACS), acute appendicitis (AA) or acute infection (ABI). The outcome measure was the time spend from the blood sample was taken to a clinical decision was made.

Results

The study period took place in October--November 2009 and from February to April 2010. 239 patients were eligible for the study. There was no difference between the groups suspected for DVT, ACS and AA, but a significant reduction in time for the ABI group (p:0.009), where the median time to decision was reduced from 7 hours and 33 minutes to 4 hours and 38 minutes when POCT was used. Only in the confirmation of ABI the time to action was significantly shorter.

Conclusions

Fast laboratory answers by POCT in an ED reduce the time to clinical decision significantly for bacterial infections. We suggest further studies which include a sufficient number of patients on deep venous thrombosis, acute appendicitis and acute coronary syndrome.