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.

Sample matrix and high-sensitivity cardiac troponin I assays.

Background Manufacturers of high-sensitivity cardiac troponin (hs-cTn) assays have restricted use of what sample types or matrices are acceptable to use for measurement. Our goal was to evaluate the comparability of the Siemens ADVIA Centaur hs-cTnI assay across different matrices and under different storage conditions. Methods Three different QC-plasma matrices were evaluated for imprecision <10 ng/L. Passing-Bablok regression and difference plots were determined for cTnI concentrations spanning the reference interval (limit of quantification to male 99th-percentile: 2.5 ng/L to <60 ng/L) between serum and lithium heparin plasma, lithium heparin and EDTA plasma and between the Siemens and Abbott hs-cTnI assays. Stability at room temperature (RT) and 2-8 °C was also assessed across the three matrices. Results Over 16-weeks the SDs were ≤1.0 ng/L for QCs ranging from 5.0 to 8.3 ng/L. Across the reference interval there was excellent agreement between lithium heparin plasma and serum for the Siemens hs-cTnI assay (slope=0.98/intercept=-0.1), however, cTnI concentrations were proportionally lower in EDTA as compared to lithium heparin plasma (slope=0.90, 95% CI: 0.88-0.92). In lithium heparin plasma the Siemens hs-cTnI concentrations were higher than the Abbott hs-cTnI concentrations (slope=1.26/intercept=-0.2). Stability of cTnI in lithium heparin plasma as compared in serum and EDTA plasma appeared more labile, with decreases ≥20% in concentrations evident as early as 1-day in storage at RT. Conclusions There is excellent agreement in concentrations between lithium heparin plasma and serum with the Siemens ADVIA Centaur hs-cTnI assay; however, cTnI concentrations in EDTA plasma are lower. Reference intervals and clinical studies in EDTA plasma for the Centaur hs-cTnI assay are required before clinical use.

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.

Genital VZV in a Third Trimester Pregnancy and the Critical Role of Interdisciplinary Planning.

Introduction: Herpes simplex (HSV) and varicella zoster (VZV) viruses are harmful infectious agents in pregnancy due to their ability to impact maternal-fetal dyads through various modalities including vertical transmission, neonatal infection, and maternal morbidity. As a result, accurate diagnosis and prompt treatment of these infections in pregnancy is critical. Case: A 19-year-old primigravida presented to our tertiary care center at 30 weeks' gestation with vulvar swelling, burning, and pain. Workup included direct PCR testing of a particularly erythematous area of the vulva which returned positive for VZV. The patient was treated with a 10-day course of acyclovir with resolution of her symptoms. She later had a full-term spontaneous vaginal delivery outside of the infectious window with no significant morbidity for either her or her neonate. Conclusion: Although a rare presentation, the presence of a genital lesion or labial swelling during pregnancy warrants workup for VZV, particularly among patients known to be varicella nonimmune. If genital VZV is diagnosed during pregnancy, the development of contingency plans through interdisciplinary collaboration should be pursued to ensure a safe delivery and postpartum course for both the maternal-fetal dyad as well as other patients on the unit and the provider care team.

Imprecision of high-sensitivity cardiac troponin assays at the female 99th-percentile.

BACKGROUND: An analytical benchmark for high-sensitivity cardiac troponin (hs-cTn) assays is to achieve a coefficient of variation (CV) of ≤ 10.0 % at the 99th percentile upper reference limit (URL) used for the diagnosis of myocardial infarction. Few prospective multicenter studies have evaluated assay imprecision and none have determined precision at the female URL which is lower than the male URL for all cardiac troponin assays. METHODS: Human serum and plasma matrix samples were constructed to yield hs-cTn concentrations near the female URLs for the Abbott, Beckman, Roche, and Siemens hs-cTn assays. These materials were sent (on dry ice) to 35 Canadian hospital laboratories (n = 64 instruments evaluated) participating in a larger clinical trial, with instructions for storage, handling, and monthly testing over one year. The mean concentration, standard deviation, and CV for each instrument type and an overall pooled CV for each manufacturer were calculated. RESULTS: The CVs for all individual instruments and overall were ≤ 10.0 % for two manufacturers (Abbott CVpooled = 6.3 % and Beckman CVpooled = 7.0 %). One of four Siemens Atellica instruments yielded a CV > 10.0 % (CVpooled = 7.7 %), whereas 15 of 41 Roche instruments yielded CVs > 10.0 % at the female URL of 9 ng/L used worldwide (6 cobas e411, 1 cobas e601, 4 cobas e602, and 4 cobas e801) (CVpooled = 11.7 %). Four Roche instruments also yielded CVs > 10.0 % near the female URL of 14 ng/L used in the United States (CVpooled = 8.5 %). CONCLUSIONS: The number of instruments achieving a CV ≤ 10.0 % at the female 99th-percentile URL varies by manufacturer and by instrument. Monitoring assay precision at the female URL is necessary for some assays to ensure optimal use of this threshold in clinical practice.

Acute Phase Response and Non-Reproducible Elevated Concentrations with a High-Sensitivity Cardiac Troponin I Assay.

High-sensitivity cardiac troponin (hs-cTn) testing has enabled physicians to make earlier diagnostic and prognostic decisions in the hospital setting than previous cardiac troponin assays. Analytical improvements have permitted one to measure cardiac troponin precisely in the nanogram per litre (ng/L) range with hs-cTn assays which has resulted in fast 0/1-h and 0/2-h algorithms for ruling-in and ruling-out myocardial infarction. Although analytical interferences that affect the reporting of hs-cTn are uncommon, not all hs-cTn assays are designed the same nor have undergone the same clinical and analytical validations. Here, after investigating an initial case of discrepant hs-cTnI results, we report that patients with an acute phase response (e.g., patients with inflammatory or infectious illnesses) can yield high and non-reproducible results with the Ortho Clinical Diagnostics hs-cTnI assay. Compared to Abbott Diagnostics hs-cTnI, Ortho Clinical Diagnostics hs-cTnI assay misclassifies biochemical injury in approximately 10% of the population being assessed for myocardial injury with imprecise results in approximately half of this population (i.e., 5%). In conclusion, caution is warranted in interpreting Ortho Clinical Diagnostics hs-cTnI alone in patients being evaluated for myocardial injury, especially in patients whose primary presentation is related to an acute phase response and not an acute coronary syndrome symptom.

Disagreement between Cardiac Troponin Tests Yielding a Higher Incidence of Myocardial Injury in the Emergency Setting.

Differences in patient classification of myocardial injury between high-sensitivity cardiac troponin (hs-cTn) assays have largely been attributed to assay design and analytical sensitivity aspects. Our objective was to compare Ortho Clinical Diagnostics' (OCD) hs-cTnI assay to OCD's contemporary/conventional assay (cTnI ES) and another hs-cTnI assay (Abbott hs-cTnI) in samples obtained from different emergency departments (EDs). Two different sample types were evaluated (lithium heparin and ethylenediaminetetraacetic acid (EDTA) plasma) in a non-selected ED population (study 1, n = 469 samples) and in patients for which ED physicians ordered cardiac troponin testing (study 2, n = 1147 samples), from five different EDs. The incidence of injury in study 1 was higher with the OCD hs-cTnI assay (30.9%; 95% CI: 26.9 to 35.2) compared to that of the Abbott hs-cTnI (17.3%; 95% CI: 14.1 to 21.0) and the OCD cTnI ES (15.4%; 95% CI: 12.4 to 18.9) assays, with repeat testing identifying 4.8% (95% CI: 3.0 to 7.5) of the OCD hs-cTnI results with poor reproducibility. In study 2, 4.6% (95% CI: 3.5 to 6.0) of the results were not reported for the OCD hs-cTnI assay (i.e., poor reproducibility) with 12.7% (95%CI: 8.7 to 17.8) of the OCD hs-cTnI results positive for injury being negative for injury with the Abbott hs-cTnI assay. In summary, the OCD hs-cTnI assay yields higher rates of biochemical injury with a higher rate of poor reproducible results in different ED populations.

Analytical characterization of the Siemens Dimension EXL high-sensitivity cardiac troponin I assay.

BACKGROUND: Siemens Healthcare Diagnostics has four commercially available assays on different analytical platforms using different methodologies to generate signal. We assessed the analytical performance of the Dimension EXL hs-cTnI assay (LOCI method) across different matrices and compared it to two different acridinium ester-based hs-cTnI assays (ADVIA Centaur and Abbott ARCHITECT). METHODS: The analytical sensitivity and precision below the 99th-percentile was determined for the Dimension EXL hs-cTnI assay. Method comparisons were performed between the Dimension EXL contemporary cTnI and the hs-cTnI assays, between different matrices for the EXL hs-cTnI assay (serum, lithium heparin and EDTA plasma), and between different hs-cTnI assays (EXL versus ADVIA Centaur or Abbott ARCHITECT) using non-parametric analyses. RESULTS: The limit of blank and detection were 0.9 ng/L and 1.7 ng/L, respectively, with imprecision of 5.8% at 8.6 ng/L and 3.2% at 47.5 ng/L. Comparison between the EXL contemporary cTnI and hs-cTnI assay (range: 2.6-4214 ng/L) yielded proportional lower concentrations for the hs-cTnI assay (slope = 0.86; 95%CI: 0.81 to 0.96, n = 40); however, there was no difference in concentrations below 100 ng/L between the assays (median difference = -2.7 ng/L; 95%CI: -9.8 to 9.3). Passing-Bablok regression analysis with EDTA plasma yielded proportionally higher concentrations with the EXL hs-cTnI versus Abbott hs-cTnI (slope = 1.45; 95%CI: 1.02-1.86, n = 40) with proportionally lower concentrations with EDTA versus lithium heparin plasma with the EXL hs-cTnI assay alone (slope = 0.93; 95%CI: 0.90 to 0.99, n = 40). Comparison with Abbott hs-cTnI concentrations below 100 ng/L in the three matrices, indicated that the EXL hs-cTnI assay yielded higher concentrations (median difference range: 3.4-9.4 ng/L), with differences also evident when comparing the EXL hs-cTnI assay to the ADVIA Centaur hs-cTnI assay. CONCLUSION: The Siemens EXL hs-cTnI assay meets the analytical criteria for a high-sensitivity assay, with assay specific cutoffs important to maximize clinical performance.

Macrocomplexes and discordant high-sensitivity cardiac troponin concentrations.

Background Analytical comparisons between different high-sensitivity cardiac troponin (hs-cTn) assays are important for reassurance of results performed with different methodologies and to identify potential interferences or confounders to result interpretation. Our objective in the present study was to compare Beckman Coulter's latest hs-cTnI assay to Abbott's hs-cTnI assay and to assess agreement between results. Methods Two hundred ethylenediaminetetraacetic acid plasma samples that had clinically reported hs-cTnI results from the Abbott ARCHITECTi2000 that spanned the analytical range were stored (median = 4 h), re-centrifuged and retested for hs-cTnI on the Abbott ARCHITECTi1000 and Beckman Coulter Access2 analysers. Passing-Bablok regression and fold-differences were evaluated, with differences approximately three-fold between results further subjected to Roche hs-cTnT testing and polyethylene glycol precipitation. Results The Beckman and Abbott hs-cTnI concentrations were correlated ( r = 0.95) with Beckman yielding proportionally lower concentrations (slope = 0.78; 95%CI: 0.74-0.85). There were 12 samples that yielded Abbott hs-TnI concentrations ≥3-fold higher than the Beckman hs-cTnI concentrations; of which nine samples from seven different patients had sufficient quantity for additional testing. All seven patients had macrocomplexes as determined with polyethylene glycol precipitation that affected the Abbott hs-cTnI assay. One patient with Abbott hs-cTnI results >1300 ng/L had polyethylene glycol, heterophile antibodies and creatine kinase-MB testing performed which confirmed that a macrocomplex most likely affected the Abbott and Roche (hs-cTnT = 65 ng/L) assays but not the Beckman (hs-cTnI = 12 ng/L) assay. Conclusion The hs-cTnI concentrations obtained from ethylenediaminetetraacetic acid plasma between the Beckman and Abbott assays are highly correlated, with large differences in concentrations (≥3-fold) between Abbott and Beckman assays possible due to macrocomplexes.

The potential role of a turbidimetric heart-type fatty acid-binding protein assay to aid in the interpretation of persistently elevated, non-changing, cardiac troponin I concentrations.

BACKGROUND: Elevated and non-changing high-sensitivity cardiac troponin (hs-cTn) concentrations may suggest a process other than acute injury, possibly due to chronic condition(s) causing the elevation, an analytical error/interference or the formation of macrocomplexes. Heart-type fatty acid binding protein (H-FABP) might be useful in this setting to identify the etiology of abnormally high and non-changing cTn concentrations which could aid clinical decision making in the hospital setting. METHODS: We analytically validated the H-FABP assay (Randox) on the Abbott ARICHTECTc8000 platform, testing imprecision, linearity, stability, and matrix comparison. Over the 2-month analytical validation; EDTA plasma samples from patients with a hospital visit with persistently elevated and stable cTnI concentrations (Abbott hs-cTnI≥52 ng/L or 2x99th percentile upper limit of normal (ULN = 26 ng/L) with change between results <20%) were collected and frozen (-20 °C). These samples were tested with the H-FABP assay, polyethylene glycol (PEG) precipitation, with the lowest estimated glomerular filtration rate (eGRF) during the hospital visit also obtained from these patients. RESULTS: The H-FABP assay was linear, with concentrations stable after 4 freeze/thaw cycles, up to 150 h at room temperature, and comparable between lithium heparin and EDTA plasma. During the validation there were 6 patients with eGFR ≥60 ml/min/1.73m2 identified (total population screened n = 917) with high and non-changing hs-cTnI concentrations. All 6 patients had H-FABP<2xULN; with 3 patients having a macrocomplex and a final diagnosis of not ACS. CONCLUSION: Testing of H-FABP in patients with an eGFR≥60 ml/min/1.73m2 with persistently high and stable cTn elevations may help to confirm prior cardiac injury or the presence of macrocomplexes as the source of these elevations.

Studies of Transgenic Mosquitoes in Disease-Endemic Countries: Preparation of Containment Facilities.

Novel approaches to area-wide control of vector species offer promise as additional tools in the fight against vectored diseases. Evaluation of transgenic insect strains aimed at field population control in disease-endemic countries may involve international partnerships and should be done in a stepwise approach, starting with studies in containment facilities. The preparations of both new-build and renovated facilities are described, including working with local and national regulations regarding land use, construction, and biosafety requirements, as well as international guidance to fill any gaps in regulation. The examples given are for containment categorization at Arthropod Containment Level 2 for initial facility design, classification of wastes, and precautions during shipping. Specific lessons were derived from preparations to evaluate transgenic (non-gene drive) mosquitoes in West and East African countries. Documented procedures and the use of a non-transgenic training strain for trial shipments and culturing were used to develop competence and confidence among the African facility staff, and along the chain of custody for transport. This practical description is offered to support other research consortia or institutions preparing containment facilities and operating procedures in conditions where research on transgenic insects is at an early stage.

A practical approach for the validation and clinical implementation of a high-sensitivity cardiac troponin I assay across a North American city.

OBJECTIVES: Despite several publications on the analytical performance of high-sensitivity cardiac troponin (hs-cTn) assays, there has been little information on how laboratories should validate and implement these assays into clinical service. Our study provides a practical approach for the validation and implementation of a hs-cTn assay across a large North American City. DESIGN AND METHODS: Validation for the Abbott ARCHITECT hs-cTnI assay (across 5 analyzers) consisted of verification of limit of blank (LoB), precision (i.e., coefficient of variation; CV) testing at the reported limit of detection (LoD) and within and outside the 99th percentile, linearity testing, cTnI versus hs-cTnI patient comparison within and between analyzers (Passing and Bablok and non-parametric analyses). Education, clinical communications, and memorandums were issued in advance to inform all staff across the city as well as a selected reminder the day before live-date to important users. All hospitals switched to the hs-cTnI assay concurrently (the contemporary cTnI assay removed) with laboratory staff instructed to repeat samples previously measured with the contemporary cTnI assay with the hs-cTnI assay only by physician request. RESULTS: Across the 5 analyzers and 6 reagent packs the overall LoB was 0.6 ng/L (n=60) with a CV of 33% at an overall mean of 1.2 ng/L (n=60; reported LoD=1.0 ng/L), with linearity demonstrated from 45,005 ng/L to 1.1 ng/L. Precision testing with a normal patient-pool QC material (mean range across 5 analyzers was 3.9-4.4 ng/L) yielded a range of CVs from 7% to 10% (within-run) and CVs from 7% to 18% (between-run) with the high patient-pool QC material (mean range across 5 analyzers was 29.6-36.3 ng/L) yielding a range of CVs from 2% to 5% (within-run) and CVs from 4% to 8% (between-run). There was agreement between hs-cTnI versus cTnI with the patient samples (slope ranges: 0.89-1.03; intercept ranges: 1.9-3.8 ng/L), however, the median CV on patient samples <100 ng/L across the analyzers was 5.6% for hs-cTnI versus 18.7% for the contemporary assay (p<0.001). Following the switch to hs-cTnI testing, no requests for repeat measurements were received. CONCLUSIONS: Validation and implementation of hs-cTnI testing across multiple sites requires collaboration within the laboratories and between hospital laboratories and clinical staff.