Analytical evaluation of the new Beckman Coulter Access high sensitivity cardiac troponin I immunoassay

A Comparison Study: Possible Bias in Troponin I Measurement Obtained with a Point of Care Testing and a Central Laboratory Analyzers Employing Different Biological Matrices and Anticoagulants

BACKGROUND

high-sensitive cardiac TroponinI (hs-cTnI) is widely used for diagnosis of acute coronary syndromes. The latest recommendation for hs-cTnI determination is the protocol 0-1 h finalized to improve the rule out accuracy of the test. A Point of Care Testing able to guarantee these performances could be very useful due to reducing the turnaround time and ruling out patients suspected of ACS, especially by using biological matrices that are not required for centrifuge. The aim of our work is to compare the results for hs-cTnI obtained using different biological matrices and anticoagulants, obtained between Atellica® VTLi hs-cTnI POCT and Access AccuTnI+3 DxI800 performances, in order to establish a possible bias derived directly from these pre-analytical conditions.

METHODS

Li-heparinized pool samples were primary employ for hs-cTnI with Atellica® VTLi as whole blood, then centrifuged and tested on Atellica® VTLi and DxI800. K3EDTA pool samples were centrifuged and measured on DxI800 too. A comparison of methods was performed according to CLSI_EP-09A2 protocol. Constant and proportional errors were investigated with Deming regression. Bias between methods was evaluated with the Bland Altman test.

RESULTS

comparing whole blood lithium heparin results obtained with Atellica versus lithium heparin and K3EDTA plasma tested on DxI 800, the Deming regression revealed a proportional error, whereas in both cases Bland Altman highlighted a minimal underestimation. A similar performance was revealed when considering plasma lithium heparin tested on Atellica versus lithium heparin and K3EDTA plasma obtained with DxI800, confirming the same underestimation. Considering values close to the cut off, no significant differences were found.

CONCLUSIONS

in the laboratory, the estimation of the bias of two different analyzers is pivotal. Once more this is crucial when different biological matrices and anticoagulants are employed for the analysis. Our study demonstrates that no significant differences among the two matrices are present when comparing Atellica and DxI800 performances.

Analytical evaluation of the novel Mindray high sensitivity cardiac troponin I immunoassay on CL-1200i

OBJECTIVES

The current study was designed to evaluate the analytical performance of the new Mindray highly sensitive cardiac troponin I (hs-cTnI) chemiluminescent immunoassay on Mindray CL-1200i, as a thorough validation of novel hs-cTnI methods is required before introduction into clinical practice.

METHODS

The evaluation of the analytical performance of this hs-cTnI immunoassay encompassed the calculation of the limit of blank (LOB), limit of detection (LOD), functional sensitivity, imprecision, linearity, 99th percentile upper reference limit (URL) and concordance with another previously validated hs-cTnI chemiluminescent immunoassay.

RESULTS

The LOB and LOD were 0.32 and 0.35 ng/L, whilst the functional sensitivity (expressed as cTnI value with <10 % imprecision), was 0.35 ng/L. The linearity was excellent throughout a wide range of clinically measurable values (r=1.00 between 0.8 and 9,726.9 ng/mL). The intra-assay, inter-assay and total imprecision were 1.1-1.3 %, 5.5-8.1 % and 5.6-8.2 %, respectively. The 99th percentile URL calculated using residual plasma from 246 ostensibly healthy blood donors was 9.2 ng/L (4.3 ng/L in women vs. 12.3 ng/L in men). The Spearman's correlation between Mindray hs-cTnI and Access hs-TnI was 0.97, with mean bias of 7.2 % (95 % CI, 2.6-11.9 %).

CONCLUSIONS

Although we failed to confirm the very optimistic analytical characteristics previously reported for this method, our evaluation of the novel Mindray hs-cTnI immunoassay on CL-1200i demonstrated that the overall performance is comparable to that of other commercially available hs-cTnI techniques, making it a viable alternative to other methods.

Emergency Department Referral of Patients With Chest Pain for Noninvasive Cardiac Testing and 2-Year Clinical Outcomes

BACKGROUND

Noninvasive cardiac testing (NICT) has been associated with decreased long-term risks of major adverse cardiac events (MACEs) among emergency department patients at high coronary risk. It is unclear whether this association extends to patients without evidence of myocardial injury on initial ECG and cardiac troponin testing.

METHODS

A retrospective cohort study was conducted of patients presenting with chest pain between 2013 and 2019 to 21 emergency departments within an integrated health care system in Northern California, excluding patients with ST-segment-elevation myocardial infarction or myocardial injury by serum troponin testing. To account for confounding by indication, we grouped patient encounters by the NICT referral rate of the initially assigned emergency physician relative to local peers within discrete time periods. The primary outcome was MACE within 2 years. Secondary outcomes were coronary revascularization and MACE, inclusive of all-cause mortality. Associations between the NICT referral group (low, intermediate, or high) and outcomes were assessed using risk-adjusted proportional hazards methods with censoring for competing events.

RESULTS

Among 144 577 eligible patient encounters, the median age was 58 years (interquartile range, 48-68) and 57% were female. Thirty-day NICT referral was 13.0%, 19.9%, and 27.8% in low, intermediate, and high NICT referral groups, respectively, with a good balance of baseline covariates between groups. Compared with the low NICT referral group, there was no significant decrease in the adjusted hazard ratio of MACE within the intermediate (adjusted hazard ratio, 1.08 [95% CI, 1.02-1.14]) or high (adjusted hazard ratio, 1.05 [95% CI, 0.99-1.11]) NICT referral groups. Results were similar for MACE, inclusive of all-cause mortality, and coronary revascularization, as well as subgroup analyses stratified by estimated risk (history, electrocardiogram, age, risk factors, troponin [HEART] score: percent classified as low risk, 48.2%; moderate risk, 49.2%; and high risk, 2.7%).

CONCLUSIONS

Increases in NICT referrals were not associated with changes in the hazard of MACE within 2 years following emergency department visits for chest pain without evidence of acute myocardial injury. These findings further highlight the need for evidence-based guidance regarding the appropriate use of NICT in this population.

Frequency histograms of three high-sensitivity cardiac troponin assays in a reference population

Background

Cardiac troponin (cTn) values above the 99th percentile upper reference limit (URL) indicate myocardial injury. We established 99th percentile URLs for three high‐sensitivity cTn (hs‐cTn) assays (Beckman Coulter Access hs‐cTnI, Abbott STAT hs‐cTnI, and Roche Elecsys hs‐cTnT) using a healthy population in Korea.

Methods

Each cTn value was measured by three assays and analyzed by dividing by gender and age.

Results

The frequency histograms of log‐transformed cTn values for Beckman and Abbott assays exhibited a bell‐shaped distribution. The 99th percentile URLs were 9.8, 17.4, and 17.3 ng/L in the total population; 10.9/9.0, 18.9/17.0, and 18.9/17.7 ng/L in the male/female population (p < 0.001 for all three assays); and 11.2/7.2, 19.9/14.5, and 22.7/9.3 ng/L in the older/younger population (p < 0.001 for all three assays) for Beckman, Abbott, and Roche assays, respectively.

Conclusion

Among the three assays, bell‐shaped distributions were observed in a frequency histogram of log‐transformed cTn values for healthy population in Beckman and Abbott assays. Also, our findings show that the 99th percentile URLs for cTn levels vary not only by gender but age.

Baseline High Sensitivity Cardiac Troponin I Level Below Limit of Quantitation Rules Out Acute Myocardial Infarction in the Emergency Department

The objective of our study was to determine the utility of a baseline high sensitivity cardiac troponin (hs-cTnI) value below the limit of quantitation to rule-out acute myocardial infarction (AMI) in patients presenting to the emergency department (ED) with any suspicious symptoms of a cardiac etiology. We enrolled subjects presenting to the ED with symptoms suspicious for AMI. Blood specimens were collected within 1 hour after a triage electrocardiogram. Cardiac troponin I was measured using the Beckman Coulter Access hs-cTnI assay. The diagnosis of AMI was adjudicated by 2 cardiologists using the Third Universal Definition of AMI and Roche Diagnostics Troponin T Generation 5 assay with all available clinical data at 30 days after presentation. A total of 567 subjects had all data required for data analyses. AMI was diagnosed in 46 (8.1%) patients. Two hundred thirty-two (40.9%) individuals had presentation hs-cTnI results <4.0 ng/L. None of the patients with baseline hs-cTnI <4.0 ng/L had an AMI, yielding a negative predictive value of 100.0% and a sensitivity of 100%, and a good prognosis (no AMIs or cardiac-related deaths at 30 days). In this single-center ED study, a baseline presenting novel hs-cTnI value of <4.0 ng/L effectively ruled out AMI in 40.9% of all patients presenting to the ED and having any symptoms suspicious for AMI. Importantly all patients, not only those with chest pain, and those having symptoms for any duration or those with end-stage renal disease requiring dialysis were included.

Prognostic value of troponin I in atrial fibrillation

OBJECTIVE

To evaluate whether circulating cardiac troponin I (cTnI) levels are associated with worst outcomes in patients with atrial fibrillation (AF).

METHODS

Consecutive patients visiting the emergency room (ER) with a new episode of a previously diagnosed AF or a new diagnosis of AF during ER admission between January 1st, 2010 and December 31st, 2015, were enrolled in the study (n = 2617). After applying exclusion criteria and eliminating repeated episodes, 2013 patients were finally included. Of these, 1080 patients with at least one cTnI measurement in the ER were selected and classified into 4 groups according to cTnI quartiles: Q1 (n = 147) cTnI <10 ng/L (Group 1); Q2 (n = 254): 10-19 ng/L (Group 2); Q3 (n = 409): 20-40 ng/L (Group 3); and Q4 (n = 270): cTnI >40 ng/L (Group 4). The median follow-up period was 47.8 ± 32.8 months. The primary endpoint was all-cause death during the follow-up.

RESULTS

A higher mortality was found in group 4 compared with the other groups (58.9% vs. 28.5%, respectively, p < 0.001), along with, hospitalizations (40.4% vs. 30.7%, p = 0.004), and readmissions due to decompensated heart failure (26.7% vs. 2.5%, p = 0.002). The probability of survival without AF recurrences was lower in the Q4 (p = 0.045). Moreover, cTnI levels >40 ng/L (Q4) were an independent risk factor of death (HR, 2.03; 95% CI, 1.64-2.51; p < 0.001).

CONCLUSION

The assessment of cTnI at ER admission could be a useful strategy for risk stratification of patients diagnosed with AF by identifying a subgroup with medium-term to long-term increased risk of adverse events and mortality.

Analytical assessment of ortho clinical diagnostics high-sensitivity cardiac troponin I assay

Objectives

To analytically evaluate Ortho Clinical Diagnostics VITROS high-sensitivity cardiac troponin I (hs-cTnI) assay in specific matrices with comparison to other hs-cTn assays.

Methods

The limit of detection (LoD), imprecision, interference and stability testing for both serum and lithium heparin (Li-Hep) plasma for the VITROS hs-cTnI assay was determined. We performed Passing-Bablok regression analyses between sample types for the VITROS hs-cTnI assay and compared them to the Abbott ARCHITECT, Beckman Access and the Siemens ADVIA Centaur hs-cTnI assays. We also performed Receiver-operating characteristic curve analyses with the area under the curve (AUC) determined in an emergency department (ED)-study population (n=131) for myocardial infarction (MI).

Results

The VITROS hs-cTnI LoD was 0.73 ng/L (serum) and 1.4 ng/L (Li-Hep). Stability up to five freeze-thaws was observed for the Ortho hs-cTnI assay, with the analyte stability at room temperature in serum superior to Li-Hep with gross hemolysis also affecting Li-Hep plasma hs-cTnI results. Comparison of Li-Hep to serum concentrations (n=202), yielded proportionally lower concentrations in plasma with the VITROS hs-cTnI assay (slope=0.85; 95% confidence interval [CI]:0.83-0.88). In serum, the VITROS hs-cTnI concentrations were proportionally lower compared to other hs-cTnI assays, with similar slopes observed between assays in samples frozen <-70 °C for 17 years (ED-study) or in 2020. In the ED-study, the VITROS hs-cTnI assay had an AUC of 0.974 (95%CI:0.929-0.994) for MI, similar to the AUCs of other hs-cTn assays.

Conclusions

Lack of standardization of hs-cTnI assays across manufacturers is evident. The VITROS hs-cTnI assay yields lower concentrations compared to other hs-cTnI assays. Important differences exist between Li-Hep plasma and serum, with evidence of stability and excellent clinical performance comparable to other hs-cTn assays.

Implications of myocardial injury in Mexican hospitalized patients with coronavirus disease 2019 (COVID-19)

Background

Respiratory illnesses is the most common manifestation of Coronavirus disease 2019 (COVID-19); however, myocardial injury has recently emerged as a frequent complication.

Methods

An observational, longitudinal, prospective, and multicenter study of hospitalized Mexican patients was made. We assessed the prevalence of myocardial injury and its relationship with complications and mortality.

Results

254 COVID-19 patients were included. Their average age was 53.8 years old, 167 (65.7%) were male and 87 (34.3%) female. According to troponin levels, two populations were generated, those with and without myocardial injury. There was no difference in gender or age between both groups. However, there was a greater proportion of obesity and hypertension in myocardial injury group. Multivariate logistic regression analysis revealed that obesity (OR 2.029, 95% CI 1.039–3.961; p = 0.038), arterial oxygen saturation <90% (OR 2.250, 95% CI 1.216–3.560; p = 0.025), and systolic blood pressure <90 mmHg (OR 2.636, 95% CI 1.530–4.343; p = 0.042), were directly related to higher levels of troponins. Multivariate cox proportional hazards analysis showed that primary endpoint (mortality) was determined by overweight/obesity (OR 1.290, 95% CI 0.115–0.730; p = 0.009), ferritin levels (OR 1.001, 95% CI 1.000–1.001; p < 0.001), myocardial injury (OR 3.764, 95% CI 1.307–10.838; p = 0.014), septic shock (OR 4.104, 95% CI 1.142–14.132; p = 0.024), acute respiratory distress syndrome (OR 3.001, 95% CI 1.008–10.165; p = 0.040), and treatment with Hydroxychloroquine/Azithromycin (OR 0.357, 95% IC 0.133–0.955; p = 0.040). Secondary endpoint (Mechanical ventilation risk) was associated to the same factors.

Conclusions

Myocardial injury represents an increased risk of complications and death in Mexican hospitalized patients with COVID-19.

Myocardial Infarction Can Be Safely Excluded by High-sensitivity Troponin I Testing 3 Hours After Emergency Department Presentation

BACKGROUND

The accuracy and speed by which acute myocardial infarction (AMI) is excluded are an important determinant of emergency department (ED) length of stay and resource utilization. While high-sensitivity troponin I (hsTnI) >99th percentile (upper reference level [URL]) represents a "rule-in" cutpoint, our purpose was to evaluate the ability of the Beckman Coulter hsTnI assay, using various level-of-quantification (LoQ) cutpoints, to rule out AMI within 3 hours of ED presentation in suspected acute coronary syndrome (ACS) patients.

METHODS

This multicenter evaluation enrolled adults with >5 minutes of ACS symptoms and an electrocardiogram obtained per standard care. Exclusions were ST-segment elevation or chronic hemodialysis. After informed consent was obtained, blood samples were collected in heparin at ED admission (baseline), ≥1 to 3, ≥3 to 6, and ≥6 to 9 hours postadmission. Samples were processed and stored at -20°C within 1 hour and were tested at three independent clinical laboratories on an immunoassay system (DxI 800, Beckman Coulter). Analytic cutpoints were the URL of 17.9 ng/L and two LoQ cutpoints, defined as the 10 and 20% coefficient of variation (5.6 and 2.3 ng/L, respectively). A criterion standard MI diagnosis was adjudicated by an independent endpoint committee, blinded to hsTnI, and using the universal definition of MI.

RESULTS

Of 1,049 patients meeting the entry criteria, and with baseline and 1- to 3-hour hsTnI results, 117 (11.2%) had an adjudicated final diagnosis of AMI. AMI patients were typically older, with more cardiovascular risk factors. Median (IQR) presentation time was 4 (1.6-16.0) hours after symptom onset, although AMI patients presented ~0.5 hour earlier than non-AMI. Enrollment and first blood draw occurred at a mean of ~1 hour after arrival. To evaluate the assay's rule-out performance, patients with any hsTnI > URL were considered high risk and were excluded. The remaining population (n = 829) was divided into four LoQ relative categories: both hsTnI < LoQ (Lo-Lo cohort); first hsTnI < LoQ and 2nd > LoQ (Lo-Hi cohort); first > LoQ and second < LoQ (Hi-Lo cohort); or both > LoQ (Hi-Hi cohort). In patients with any hsTnI result <20% CV LoQ (Groups 1-3), n = 231 (23.9% ruled out), AMI negative predictive value (NPV) was 100% (95% confidence interval [CI] = 98.9% to 100%). In patients with any hsTnI below the 10% LoQ, n = 611 (58% rule out), AMI NPV was 100% (95% CI = 99.5% to 100%). Of the Hi-Hi cohort (i.e., no hsTnI below the 10% LoQ, but both < URL), there were four AMI patients, NPV was 98.2% (95% CI = 95.4% to 99.3%), and sensitivity was 96.6.

CONCLUSIONS

Patients presenting >3 hours after the onset of suspected ACS symptoms, with at least two Beckman Coulter Access hsTnI < URL and at least one of which is below either the 10 or the 20% LoQ, had a 100% NPV for AMI. Two hsTnI values 1 to 3 hours apart with both < URL, but also >LoQ had inadequate sensitivity and NPV.

Analytical and clinical characterization of a novel high-sensitivity cardiac troponin assay in a United States population

BACKGROUND

Cardiac troponin (cTn) is the keystone for diagnosis of acute myocardial infarction (AMI). We examined the analytical and clinical diagnostic characteristics of the ACCESS hsTnI assay in a United States (US) population.

METHODS

All measurements and studies were conducted using a lithium heparin matrix. Sex-specific 99th percentile upper reference limits (URLs) were determined for 1089 healthy women (54.6%) and men using non-parametric statistics. High-sensitivity (hs) performance was assessed to determine if the total CV was ≤10% at sex-specific URLs, and if ≥50% of cTnI values for each sex exceeded the assay's limit of detection (LoD). Precision, analytical measurement range, high-dose hook effect, and endogenous/exogenous interferences were examined with CLSI guidance. Clinical characterization included serial sampling of 1854 suspected AMI subjects presenting to 14 US Emergency Departments. AMI was adjudicated by a panel of expert cardiologists. The study's only exclusion was end stage renal disease.

RESULTS

99th percentile URLs were 11.6-, 19.8- and 17.5-ng/L for respective female, male and all-subject populations. Total %CV was <8% from 6.8 to 19,000 ng/L, and <6% at sex-specific 99th percentiles; ≥99% of ACCESS hsTnI values for each sex exceeded the LoD. No high-dose hook effect or endogenous/exogenous interferences were identified. A comparison of Baseline samples collected at ≤1 h and any-time after presentation, found 4% lower sensitivity for AMI than with earlier sampling. For 1-9 h post presentation, the sensitivity was >90%, specificity >85%; and negative and positive predictive value were ≥99% and >60%, respectively.

CONCLUSION

Analytical and clinical performance of the ACCESS hsTnI assay meets the definition of a hs cTn method. The ACCESS hsTnI assay has good precision over a wide range, no significant interferences, and sensitivity >90% and NPV ≥99%. Performance is appropriate for aiding in AMI diagnosis.

Diagnosis and prognosis of myocardial infarction on a plasmonic chip

Cardiovascular diseases lead to 31.5% of deaths globally, and particularly myocardial infarction (MI) results in 7.4 million deaths per year. Diagnosis of MI and monitoring for prognostic use are critical for clinical management and biomedical research, which require advanced tools with accuracy and speed. Herein, we developed a plasmonic gold nano-island (pGold) chip assay for diagnosis and monitoring of MI. On-chip microarray analysis of serum biomarkers (e.g., cardiac troponin I) afforded up to 130-fold enhancement of near-infrared fluorescence for ultra-sensitive and quantitative detection within controlled periods, using 10 μL of serum only. The pGold chip assay achieved MI diagnostic sensitivity of 100% and specificity of 95.54%, superior to the standard chemiluminescence immunoassay in cardiovascular clinics. Further, we monitored biomarker concentrations regarding percutaneous coronary intervention for prognostic purpose. Our work demonstrated a designed approach using plasmonic materials for enhanced diagnosis and monitoring for prognostic use towards point-of-care testing.

Improved efficiency and cost reduction in the emergency department by replacing contemporary sensitive with high-sensitivity cardiac troponin immunoassay

BACKGROUND

Although unquestionable evidence has been provided that high-sensitive (HS) cardiac troponin (cTn) immunoassay outperform the former contemporary-sensitive techniques, some clinicians are still hesitant to implement HS methods in routine clinical practice. This study was hence planned to evaluate the impact of replacing a contemporary-sensitive with HS cTnI immunoassay on hospital and laboratory workload.

METHODS

Information on the total number of cTnI tests ordered, total number of blood samples collected, total number of CK-MB tests ordered, number of patients with the first HS-cTnI value below the limit of detection (LoD) and cumulative HS-cTnI values was extracted from the local hospital information system for the semesters before and after the HS method was introduced.

RESULTS

Although the total emergency department (ED) visits modestly increased after introducing HS-cTnI, the number of total cTnI tests declined by over 10%. A substantial reduction of single-sample test requests was noted, accompanied by a considerable decline of 3- and 4-sample collections (i.e., -61% and -73%, respectively). A high percentage of patients (27.5%) displayed HS-cTnI values

CONCLUSION

The results of this study show substantial organizational and economic benefits by replacing contemporary-sensitive with HS cTnI immunoassays. (www.actabiomedica.it).

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Key Words

• cardiac troponin
• high-sensitivity
• myocardial infarction
• acute coronary syndrome
• emergency department

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MESH Headings

• Acute Coronary Syndrome/blood
• Acute Coronary Syndrome/diagnosis
• Cost Savings
• Emergency Service, Hospital/economics
• Female
• Humans
• Immunoassay/economics
• Male
• Retrospective Studies
• Sensitivity and Specificity
• Troponin I/blood

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Affiliation(s)

Rosalia Aloe University Hospital of Parma.
Giuseppe Lippi
Martina Di Pietro
Laura Bonfanti
Mariella Dipalo
Ivan Comelli
Paola Avanzini
Fabian Sanchis-Gomar
Gianfranco Cervellin

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High-Sensitivity Troponin I in Hospitalized and Ambulatory Patients With Heart Failure With Preserved Ejection Fraction: Insights From the Heart Failure Clinical Research Network

Background We sought to study the prevalence of high-sensitivity troponin and its association with cardiac structure and outcomes in ambulatory and hospitalized patients with heart failure with a preserved ejection fraction ( HF p EF ). Methods and Results A post hoc analysis utilized data from HF p EF patients: DOSE (Diuretic Optimization Strategies Evaluation) and CARRESS - HF (Cardiorenal Rescue Study in Acute Decompensated Heart Failure) enrolled patients hospitalized with acute HF p EF , and RELAX (Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in Heart Failure With Preserved Ejection Fraction) enrolled ambulatory patients with HF p EF . High-sensitivity troponin I (hs-TnI) was measured in hospitalized patients at baseline, at 72 to 96 hours, on day 7, and on day 60. In ambulatory patients hs-TnI was measured at baseline and at week 24. In the ambulatory cohort, correlations between hs-TnI and cardiac structure and function were assessed. The association between hs-TnI and a 60-day composite of emergency room visits, readmissions, and death was assessed for hospitalized patients using multivariable Cox proportional hazard models. The study population included 139 hospitalized and 212 ambulatory patients with HF p EF and hs-TnI measured at baseline. The median (25th, 75th percentiles) baseline troponin was 17.6 (11.1, 41.0) ng/L in hospitalized patients and 9.5 (5.3, 19.7) ng/L in ambulatory patients ( P<0.001). The prevalence of elevated hs-TnI (>99% percentile upper reference limit was 86% in hospitalized patients and 53% among ambulatory patients, with stable elevation in ambulatory patients during follow-up. HF p EF patients with a hs-TnI above the median were older with worse left ventricular hypertrophy and diastolic dysfunction. Continuously valued hs-TnI (per doubling) was associated with increased risk of composite end point (adjusted hazard ratio 1.20, 95% confidence interval 1.00-1.43; P=0.042). Conclusions Hs-TnI is commonly elevated among both hospitalized and ambulatory patients with HF p EF . Increased hs-TnI levels are associated with worse cardiac structure and increased risk of adverse events.

Evaluation of 99th percentile and reference change values of a high-sensitivity cTnI method: A multicenter study

BACKGROUND

The Italian Society of Clinical Biochemistry (SIBioC) and the Italian Section of the European Ligand Assay Society (ELAS) have recently promoted a multicenter study (Italian hs-cTnI Study) with the aim to accurately evaluate analytical performances and reference values of the most popular cTnI methods commercially available in Italy. The aim of this article is to report the results of the Italian hs-cTnI Study concerning the evaluation of the 99th percentile URL and reference change (RCV) values around the 99th URL of the Access cTnI method.

MATERIALS AND METHODS

Heparinized plasma samples were collected from 1306 healthy adult volunteers by 8 Italian clinical centers. Every center collected from 50 to 150 plasma samples from healthy adult subjects. All volunteers denied the presence of chronic or acute diseases and had normal values of routine laboratory tests (including creatinine, electrolytes, glucose and blood counts). An older cohort of 457 adult subjects (mean age 63.0 years; SD 8.1 years, minimum 47 years, maximum 86 years) underwent also ECG and cardiac imaging analysis in order to exclude the presence of asymptomatic cardiac disease.

RESULTS AND CONCLUSIONS

The results of the present study confirm that the Access hsTnI method using the DxI platform satisfies the two criteria required by international guidelines for high-sensitivity methods for cTn assay. Furthermore, the results of this study confirm that the calculation of the 99th percentile URL values are greatly affected not only by age and sex of the reference population, but also by the statistical approach used for calculation of cTnI distribution parameters.

Assessment of Access hsTnI 99th percentiles upper reference limits following IFCC recommendations

BACKGROUND

The detection of an increase and/or decrease of cardiac troponin (cTnI) values, with at least one value above the 99th percentile of the upper reference limit (URL) have a central role in acute myocardial infarction (AMI) diagnosis. The employment of sex specific 99th percentile URLs and High-sensitivity (Hs) assays are recommended. We assessed sex specific 99th percentile URL for Access Hs-cTnI and AccuTnI3+ (Beckman Coulter) using European donor reference population following recent International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommendations.

METHODS

300 males and 300 females plasma samples were collected. Both chemiluminescent immunoenzymatic assays were performed on UniCel DxI 800 platform (Beckman Coulter).

RESULTS

For Access hsTnI, the observed sex-specific 99th percentile URLs were 5.5 (90% CI: 4.4-7.6) for females and 13.9 ng/L (90% CI: 7.4-17.4) for males. For AccuTnI+3 we could not establish them because the assay couldn't report detectable values of troponin for most of the analyzed samples.

CONCLUSION

The sex-specific 99th percentile URLs established for Access hsTnI assay were significantly lower than those declared by the manufacturer caused by the different choice of population selection, age groups and sample types: for those reasons, we maintain the 99th URLs provided by manufacturer.

"Ultra-sensitive" cardiac troponins: Requirements for effective implementation in clinical practice

The measurement of cardiac troponins, either cardiac troponin I or T, has become the culprit of clinical decision making in patients with suspected acute coronary syndrome (ACS), especially in those with non-ST elevation myocardial infarction (NSTEMI). The leading analytical mainstays of cardiac troponin immunoassays include the limit of blank (LoB), limit of detection (LoD), functional sensitivity, the 99th percentile of a healthy reference population, along with the percentage of "ostensibly healthy" subjects displaying measurable values < 99th percentile. The latest generation of cardiac troponin immunoassays, conventionally defined as "high-sensitive" (HS), is characterized by a LoD over 100-fold lower compared to the first commercialized techniques and a percentage of measurable values consistently > 50% in the general healthy population. The very recent commercialization of methods with further improved analytical sensitivity (i.e., "ultra-sensitive" assays), which allow to measure cardiac troponin values in the vast majority of healthy subjects, is now challenging the diagnostic paradigm based on early rule-out of subjects with cardiac troponin values comprised between the 99th percentile and LoD. New diagnostic strategies, entailing assay-specific cut-offs, must hence be developed and validated in large multicenter studies. The aim of this article is to provide an update on commercially available HS and "ultra"-sensitive techniques for measuring cardiac troponins, along with possible implications of increasingly enhanced analytical sensitivity on diagnostic algorithms for evaluating patients with suspected ACS.

Assessing matrix, interferences and comparability between the Abbott Diagnostics and the Beckman Coulter high-sensitivity cardiac troponin I assays

Background:

Analytical evaluation of high-sensitivity cardiac troponin (hs-cTn) assays, with particular attention to imprecision, interferences and matrix effects, at normal cTn concentrations, is of utmost importance as many different clinical algorithms use concentration cutoffs <10 ng/L for decision-making. The objective for the present analytical study was to compare the new Beckman Coulter hs-cTnI assay (Access hsTnI) to Abbott’s hs-cTnI assay in different matrices and for different interferences, with a focus on concentrations <10 ng/L.

Methods:

The limit of blank (LoB) and the limit of detection (LoD) were determined in different matrices for the Beckman hs-cTnI assay. Passing-Bablok regression and difference plots were determined for 200 matched lithium heparin and EDTA plasma samples for the Beckman assay and 200 lithium heparin samples for the Abbott assay. Both EDTA and heparin plasma samples were also evaluated for stability under refrigerated conditions, for endogenous alkaline phosphatase interference and for hemolysis and icterus.

Results:

The Beckman hs-cTnI assay LoB was 0.5 ng/L with the following range of LoDs=0.8–1.2 ng/L, with EDTA plasma yielding lower concentrations as compared to lithium heparin plasma (mean difference=−14.9%; 95% CI=−16.9 to 12.9). Below 10 ng/L, lithium heparin cTnI results from the Beckman assay were on average 1.1 ng/L (95% CI=0.7 to 1.5) higher than the Abbott results, with no difference between the methods when using EDTA plasma (mean difference =−0.1 ng/L; 95% CI=−0.3 to 0.2). Low cTnI concentrations were less effected by interferences in EDTA plasma.

Conclusions:

The Access hsTnI method can reliably detect normal cTnI concentrations with both lithium heparin and EDTA plasma being suitable matrices.