Evaluating the performance of an updated high-sensitivity troponin T assay with increased tolerance to biotin.

OBJECTIVES: Biotin >20 ng/mL may interfere with the Elecsys® Troponin T-high sensitive assay (cTnT-hs; Roche Diagnostics International Ltd). We evaluated the performance of an updated assay, cTnT-hs*, which was designed to reduce biotin interference. METHODS: cTnT-hs* assay performance was assessed using up to two applications (18 min/9 min) on three analyzers (cobas e 411/cobas e 601/cobas e 801). Biotin interference was determined by measuring recovery in an 11-sample series dilution with biotin ranging from 0-3600 ng/mL. Repeatability/reproducibility were evaluated in five serum sample pools (n=75 each). Method comparisons tested: cTnT-hs* vs. cTnT-hs (18 min/cobas e 601); cTnT-hs* assay 18 vs. 9 min (cobas e 601); cTnT-hs* (18 min) on cobas e 601 vs. cobas e 411 and cobas e 601 vs. cobas e 801. Concordance at the 99th percentile decision limit between cTnT-hs* and cTnT-hs (9 min/cobas e 601) was calculated using 300 lithium-heparin plasma samples and a 14 ng/L assay cutoff. RESULTS: cTnT-hs* assay (18 min/cobas e 601) recovery was ≥96% for biotin ≤1250 ng/mL. Across all applications/analyzers, coefficients of variation for repeatability/reproducibility with the cTnT-hs* assay were <5% in most serum sample pools (mean cardiac troponin T: 8.528-9484 ng/L). High correlation (Pearson's r=1.000) was demonstrated for all method comparisons. Concordance at the 99th percentile decision limit was high between the cTnT-hs* and cTnT-hs assays. CONCLUSIONS: The updated cTnT-hs* assay may provide greater tolerance to biotin interference, and shows good analytical and clinical agreement/concordance with the previous cTnT-hs assay.

Analytical and Clinical Validation of a Point-of-Care Cardiac Troponin T Test with an Improved Detection Limit.

BACKGROUND: The point-of-care test Roche CARDIAC POC Troponin T (PoC TnT) is an improved assay which has been developed for the Roche cobas h 232 system. METHODS: We performed a multicentre evaluation (four sites) to assess the analytical performance of the PoC TnT assay and to compare it with the central laboratory Elecsys® troponin T high sensitive (lab cTnT-hs) assay. RESULTS: The relative mean differences found in method comparisons of PoC TnT vs. lab cTnT-hs ranged from -4.1% to +6.8%. Additionally, there was good concordance between PoC TnT and lab cTnT-hs for the number of samples with troponin T values below the measuring range of 40 ng/L. Lot-to-lot differences of PoC TnT ranged from -8.6% to +4.6%. Within-series coefficients of variation (CV) resulting from 81 ten-fold measurements with patient samples were 9.3%, 11.8%, and 12.9% in the low (40 to < 200 ng/L), medium (200 to < 600 ng/L), and high (600 to 2000 ng/L) measuring range, respectively. Using the system quality control, the mean CV for between-day imprecision was 11.3%. No interference was observed by triglycerides (up to 11.4 mmol/L), bilirubin (up to 376 µmol/L), hemoglobin (up to 0.12 mmol/L), biotin (up to 30 µg/L), rheumatoid factor (up to 200 IU/mL), or with 52 standard or cardiovascular drugs at therapeutic concentrations. There was no influence on the results by varying hematocrit values in a range from 25% to 53%. However, interferences with human anti-mouse antibodies were found. No significant influence on the results was found with PoC TnT by using sample volumes between 135 to 165 µL. High troponin T concentrations up to 500 µg/L did not lead to false low results, indicating no high-concentration hook effect. No cross-reactivity was found between the PoC TnT assay and human skeletal troponin T up to 1000 µg/L (< 0.05%). Diagnostic sensitivity and specificity data of a subpopulation (23 patients) of this study are in agreement with results of another large pre-hospital study. CONCLUSIONS: The PoC TnT assay showed good analytical performance with excellent concordance with the calibration and reference laboratory method. It should therefore be suitable for its intended use in point-of-care settings.

Equal performance of novel N-terminal proBNP (Cardiac proBNP®) and established BNP (Triage BNP®) point-of-care tests.

BACKGROUND: Recently, a novel point-of-care test (POCT) for N-terminal proBNP (NTproBNP) has been introduced (Cardiac proBNP®, Roche). AIM: The aim was to compare the novel POCT for NTproBNP with the established POCT for BNP. METHODS: NTproBNP and BNP were assessed in 222 individuals with chronic heart failure (n = 151) or controls (n = 71) with both POCTs. RESULTS: NTproBNP and BNP were closely correlated upon regression analysis (r = 0.93; p < 0.01). NTproBNP and BNP were both correlated with ejection fraction and New York Heart Association stage. Receiver operating characteristic analysis yielded satisfying and equivalent predictive values for the detection of left ventricular dysfunction (ejection fraction <40%; NTproBNP: area under the curve 0.97; BNP: area under the curve 0.96; p > 0.05) and presence of New York Heart Association stage >2 (area under the curve 0.92 vs 0.91 for NT-proBNP and BNP, respectively; p > 0.05). CONCLUSION: The NTproBNP POCT allows biochemical detection of heart failure with satisfactory predictive values, is equivalent to the BNP POCT and will improve near-patient testing.

Multicentre evaluation of a second generation point-of-care assay with an extended range for the determination of N-terminal pro-brain natriuretic peptide.

BACKGROUND: In the second generation of the point-of-care (POC) assay Roche CARDIAC proBNP, the upper limit of the measuring range was extended from 3000 to 9000 ng/L. METHODS: A thirteen-site multicentre evaluation was carried out to assess the analytical performance of the POC NT-proBNP assay and to compare it with a laboratory N-terminal pro-brain natriuretic peptide (NT-proBNP) assay. RESULTS: In method comparisons of six lots of POC NT-proBNP with the lab reference method (Elecsys proBNP) mean bias ranged from -10 to +17%. In lot-to-lot comparisons all six investigated lots of POC NT-proBNP showed excellent agreement, with mean bias between -7% and +2%. The majority of all coefficients of variation obtained from ten-fold measurements using 56 native blood samples were below 8%. No interference was observed with hemolytic blood (hemoglobin concentrations up to 0.12 mmol/L), lipemic blood (triglyceride concentrations up to 14.0 mmol/L) nor icteric blood (bilirubin concentrations up to 63 micromol/L). Hematocrit values between 24% and 51% had no influence on the assay result. High NT-proBNP concentrations above the measuring range of POC NT-proBNP did not lead to false low results due to potential high-dose hook effect. Results with POC NT-proBNP were not influenced by different ambient temperatures (18 degrees C to 32 degrees C), the sample material used, nor by over- or underdosing by 15 microL compared to the regular sample volume of 150 microL. CONCLUSIONS: The POC NT-proBNP assay showed an excellent analytical performance including a good agreement with the laboratory method. The assay is therefore suitable for its intended use in point-of-care settings.

Multicentre analytical evaluation of a new point-of-care system for the determination of cardiac and thromboembolic markers.

BACKGROUND: The cobas h 232 point-of-care analyzer by Roche is the instrument successor of the Cardiac reader allowing the quantitative determination of troponin T, creatine kinase MB, myoglobin, NT-proBNP and D-dimer. METHODS: In this study 1329 patients with acute coronary syndromes, heart failure, thromboembolic or other diseases and 945 healthy donors were assessed. Comparisons versus central laboratory methods were carried out with 2379 samples from these individuals; out of these, 1591 samples gave quantitative results within the measuring range and were included in the evaluation. RESULTS: The point-of-care assays for creatine kinase MB, myoglobin, NT-proBNP and D-dimer were within a relative bias range of -5.9 to +6.9% compared to the laboratory assay. The troponin T assay showed a bias of -11.0% and after change of the calibration procedure of +1.9%. None of the five point-of-care assays had a relative difference between the new system and the precursor device that was higher than +5.0%. Within-series coefficients of variation of patient samples were found in a range from 4.8 to 14.8%. No significant interference was observed with lipemic, hemolytic and icteric blood or at different hematocrit values. CONCLUSIONS: Due to its good analytical agreement with the laboratory methods and with its precursor device, the cobas h 232 system can be reliably used to support on-site decision making for cardiovascular patients in acute and non-acute settings.

Multicentre evaluation of a new point-of-care test for the determination of CK-MB in whole blood.

BACKGROUND: The point-of-care (POC) test Roche CARDIAC CK-MB is a new assay which has been developed for the existing Roche Cardiac reader system. METHODS: We performed a multicentre evaluation at six sites to assess the analytical performance of the POC CK-MB assay and to compare it with a quantitative laboratory CK-MB assay. RESULTS: Within-series coefficients of variation (CV) resulting from 34 ten-fold measurements with patient samples ranged from 4.3% to 16.4%. Using quality control material, the mean CV values for day-to-day imprecision were 6.5% for the low level control and 8.4% for the high level control. Based upon 847 pairs of values, the mean relative bias of three independently calibrated lots of the POC CK-MB assay ranged from -6% to -11% in method comparisons with the lab CK-MB assay. The mean relative lot-to-lot differences of POC CK-MB were between -2% and +1%. No interference was observed with lipaemic blood (triglyceride concentrations up to 8.1 mmol/L), icteric blood (bilirubin concentrations up to 513 micromol/L), haemolytic blood (haemoglobin concentrations up to 0.12 mmol/L), biotin (up to 30 mg/L) and rheumatoid factor (up to 119 IU/mL), or with 53 standard or cardiological drugs even in toxic concentrations. There was no influence on the results by varying haematocrit values in the range from 21% to 54%. A slight interference with human anti-mouse antibodies type 2 was found. No significant influence on the results with POC CK-MB was found by using sample volumes between 135 and 165 microL. High CK-MB concentrations above the measuring range of POC CK-MB (1-40 microg/L) did not lead to false low results due to potential high-dose hook effect. No significant effect of sample age on recovery occurred up to a sample age of 24 h. No cross-reactivity was found between the POC CK-MB assay and either CK-MM or CK-BB. A substudy with healthy individuals confirmed the reference limits of 3.8 microg/L for females and 6.7 microg/L for males. CONCLUSIONS: The POC CK-MB assay showed a very good analytical performance with an excellent concordance with the calibration and reference laboratory method. It should be therefore suitable for its intended use in POC settings. Clin Chem Lab Med 2008;46:630-8.

Development and calibration of a new point-of-care test for the determination of NT-proBNP in whole blood.

A new point-of-care test for the determination of NT-proBNP in whole blood was developed based on the existing gold-label rapid immunoassay technology of the Roche Cardiac reader system. The novel gold-labelled monoclonal antibody recognizes NT-proBNP at amino acid sequence 27 to 31, the biotinylated polyclonal antibody recognizes sequence 39 to 50. In a model assay based upon the reference method Elecsys proBNP and with an R & D lot of the point-of-care test, this newly selected and developed combination of antibodies showed a very good correlation with the standard Elecsys proBNP assay with correlations of 0.96 or 0.94, respectively. The test was calibrated according to the existing masterlot concept of the Roche CARDIAC tests with Elecsys proBNP as a reference. In a preliminary method comparison with Elecsys proBNP the accuracy of the calibration was confirmed; the bias was between 1 and 6%. Possible reasons of approximately 1% outliers (> +/- 100%) were discussed.

Multicentre evaluation of a new point-of-care test for the determination of NT-proBNP in whole blood.

BACKGROUND: The Roche CARDIAC proBNP point-of-care (POC) test is the first test intended for the quantitative determination of N-terminal pro-brain natriuretic peptide (NT-proBNP) in whole blood as an aid in the diagnosis of suspected congestive heart failure, in the monitoring of patients with compensated left-ventricular dysfunction and in the risk stratification of patients with acute coronary syndromes. METHODS: A multicentre evaluation was carried out to assess the analytical performance of the POC NT-proBNP test at seven different sites. RESULTS: The majority of all coefficients of variation (CVs) obtained for within-series imprecision using native blood samples was below 10% for both 52 samples measured ten times and for 674 samples measured in duplicate. Using quality control material, the majority of CV values for day-to-day imprecision were below 14% for the low control level and below 13% for the high control level. In method comparisons for four lots of the POC NT-proBNP test with the laboratory reference method (Elecsys proBNP), the slope ranged from 0.93 to 1.10 and the intercept ranged from 1.8 to 6.9. The bias found between venous and arterial blood with the POC NT-proBNP method was < or =5%. All four lots of the POC NT-proBNP test investigated showed excellent agreement, with mean differences of between -5% and +4%. No significant interference was observed with lipaemic blood (triglyceride concentrations up to 6.3 mmol/L), icteric blood (bilirubin concentrations up to 582 micromol/L), haemolytic blood (haemoglobin concentrations up to 62 mg/L), biotin (up to 10 mg/L), rheumatoid factor (up to 42 IU/mL), or with 50 out of 52 standard or cardiological drugs in therapeutic concentrations. With bisoprolol and BNP, somewhat higher bias in the low NT-proBNP concentration range (<175 ng/L) was found. Haematocrit values between 28% and 58% had no influence on the test result. Interference may be caused by human anti-mouse antibodies (HAMA) types 1 and 2. No significant influence on the results with POC NT-proBNP was found using volumes of 140-165 muL. High NT-proBNP concentrations above the measuring range of the POC NT-proBNP test did not lead to false low results due to a potential high-dose hook effect. CONCLUSIONS: The POC NT-proBNP test showed good analytical performance and excellent agreement with the laboratory method. The POC NT-proBNP assay is therefore suitable in the POC setting.

Sensitivity and specificity of a quantitative point of care D-dimer assay using heparinized whole blood, in patients with clinically suspected deep vein thrombosis.

D-dimer assays are efficient in the exclusion diagnostics of deep vein thrombosis (DVT) in patients without severe concomitant diseases. We have determined diagnostic sensitivity and specificity of a new point-of-care rapid assay for quantitative determination of D-dimer in heparinized whole blood in outpatients with suspected DVT. In 19 participating centers, 637 patients were included in the study, of which 77 were excluded, the majority because of inadequate documentation of analytical quality control measures. DVT was diagnosed in 223 of the remaining 560 patients by duplex ultrasound examination. The POC D-dimer assay showed a high sensitivity of 96.9% for the diagnosis of DVT and a high specificity of 60.8% at a pre-specified cutoff of 0.5 microg/ml. For Tina-quant D-dimer, sensitivity was slightly lower at 94.9%, with a specificity of 64.8%. The VIDAS D-dimer assay showed a sensitivity of 98.2%, but specificity was 40.7%. The area under the curve (AUC +/- standard error, 95% confidence interval) was 0.879 +/- 0.019 (0.845-0.909) for POC D-dimer, 0.908 +/- 0.016 (0.877-0.934) for Tina-quant D-dimer, and 0.895 +/- 0.018 (0.862-0.922) forVIDAS D-dimer. Differences were not statistically significant. The new whole blood POC D-dimer assay is a reliable tool for exclusion of DVT in symptomatic outpatients, displaying a comparable diagnostic performance as VIDAS D-dimer and Tina-quant D-dimer assays.

Risk stratification of chest pain patients by point-of-care cardiac troponin T and myoglobin measured in the emergency department.

A prospective multicenter study including 1410 chest pain patients with suspected acute coronary syndromes was carried out to examine the predictive value of biological cardiac markers for adverse events measured by a point-of-care system. Admission cardiac troponin T (cTnT) and myoglobin were measured in parallel on a point-of-care system in the emergency department and -- together with CK-MB mass -- on lab analyzers. In a one-year follow-up, cardiac and non-cardiac death, acute myocardial infarction, unstable angina pectoris and need for revascularization were registered. Median time between onset of symptoms and admission was 285 min; 172 patients (12.2%) had no event during follow-up. If the cTnT, measured either by the point-of-care system or a conventional lab analyzer, was >0.05 microg/L, then the chance of a cardiac event during the follow-up period was doubled (18% vs. 9%). Serial cTnT measurement did not add any further value to the predictive power of the admission cTnT. Myoglobin and CK-MB mass identified increasing risk with increasing concentration quartiles; cardiac event rates were 2.8- to 4.4-fold higher between the quartiles with the lowest and those with the highest analyte concentration, respectively. There was no difference in non-cardiac death rates between any concentration quartiles. In conclusion, the prediction of clinical events by cardiac troponin T and myoglobin measured with a point-of-care analyzer in the emergency department was as good as that of the same cardiac markers and CK-MB mass measured on lab analyzers.