Search

Introduction: Brain natriuretic peptide (BNP) is produced by the ventricles of the heart and is a biomarker for heart failure. Several commercial assays are now available. We evaluated the performance characteristics of the ARCHITECT BNP assay., Methods: We evaluated the limit of blank, limit of detection, linearity and imprecision. Method comparison studies were performed with 3 other automated BNP assays including the ADVIA Centaur, AxSYM, and UniCel DxI 800 methods., Results: The mean LOB and LOD of the Architect assay were 3.5 and 5.8 ng/L, respectively. Imprecision studies yielded within run CVs of 1.1 to 5.1% and total CVs of 2.3 to 5.3% using human plasma based multi-constituent controls at concentrations of 92, 500, and 3500 ng/L. The maximum deviation from the target recovery for dilution linearity was 9.6%. Concordance with other BNP assays at a 100 ng/l cutoff was 91 to 98% and kappa statistics were 0.78 to 0.96. The mean difference between the Architect and Advia Centaur methods was positive. For the other methods, the mean difference with the Architect was negative., Conclusions: The Architect BNP assay shows good performance characteristics with total imprecision < or =5.3%. It agrees well with the Advia Centaur, AxSYM, and UniCel DxI BNP assays.

Background: We demonstrate the performance of the bioMérieux VIDAS Troponin I Ultra assay for diagnostic accuracy for detection of myocardial infarction (MI) and risk stratification., Method: cTnI was measured in 545 patients from 2 clinical centers with symptoms suggestive of ACS at admission, with an additional specimen at 4-12 h (453 patients). The 99th percentile value (0.01 microg/l) was used to assess clinical accuracy for diagnosis of acute MI. Primary endpoint for risk stratification was first of cardiac event or death in 302 patients (one center) followed for 60 days., Results: 157 (28.8%) patients ruled in for an MI during index hospitalization. Sensitivities and specificities were 88.1% (95% CI 81.9 to 92.4%) and 79.9% (CI 75.5 to 83.6%) for baseline and 100% (CI 96.5 to 100%) and 79.4% (CI 74.4 to 83.4%) for follow-up specimens. ROC curve areas increased from 0.912 (CI 0.879 to 0.944) at baseline to 0.994 (CI 0.988 to 0.999) at second sampling (n=453, p<0.01); with no differences between sites. Primary endpoint rate for the 223 patients (74%) with normal cTnI on presentation was lower than the 79 patients (26%) with cTnI>0.01 ug/l (5.9% vs. 42.3%, p<0.0001). The relative risk for the >0.01 ug/l group was 8.9 (CI 4.6 to 17)., Conclusion: The VIDAS cTnI assay is a sensitive diagnostic method for the early detection of MI and predicts increased risk for adverse events in patients with symptoms suggestive of ACS.

Background: Measurement of amino-terminal pro-B-type natriuretic peptide (NT-proBNP) is useful for evaluating patients with heart failure (HF)., Methods: We evaluated the performance of a new automated NT-proBNP assay., Results: The VITROS NT-proBNP assay had mean within-run and total imprecision of 1.0% and 3.4% at NT-proBNP concentrations from 67-27,500 ng/l. Acceptable linearity, functional/analytical sensitivity were demonstrated. Anticoagulant/tube types had no effect on results. Excellent sample stability and no high-dose hook were observed. High correlation between the VITROS and Elecsys methods was demonstrated (r=0.995; P<.001), with 98.3% clinical concordance. VITROS NT-proBNP concentrations were significantly higher in HF subjects than those without (1210 versus 68 ng/l; P<.001) and associated with HF symptom severity (P<.001). The VITROS assay had AUC for HF of 0.95 (P<.001), and had excellent NPV for excluding HF., Conclusions: The automated VITROS NT-proBNP assay demonstrates excellent analytical and clinical performance for evaluating the presence and severity of HF.

Background: NT-proBNP measurements aid in the evaluation of patients with suspected heart failure (HF) and may facilitate risk stratification in patients with HF and acute coronary syndrome (ACS). Point-of-care (POC) assays may provide more timely results and potentially improve patient outcomes., Methods: We evaluated the analytical performance of the Response Biomedical Corporation whole blood RAMP amino-terminal pro-B type natriuretic peptide (NT-proBNP) POC assay compared to the Roche Elecsys proBNP (NT-proBNP) assay., Results: Intra-day and total imprecision (% CV) ranged from 5.5% to 10.3% at 140, 449 and 1675 ng/L. The lowest concentration that yields a 20% CV was 57 ng/L. The lower limit of detection was 18 ng/L. The upper limit of linearity was validated to 23,428 ng/L with an average recovery of 95%. Correlation by Passing and Bablok regression yielded RAMP=1.01 Elecsys+14.6, r=0.98 (n=540; range of Elecsys values <5 to >35,000). Concordance of RAMP versus Elecsys using cut-offs of 125 ng/L for subjects <75 years and 450 ng/L for subjects > or =75 was 92% (95% CI 89-94%) for a group consisting of 127 apparently healthy individuals and 208 non-healthy subjects without HF, and 99% (95% CI 97-100%) for patients with HF, using the New York Heart Association (NYHA) functional classification. Overall, 80%, 87%, 97% and 100% of the RAMP results and 77%, 85%, 96% and 100% of the Elecsys results were greater than the age appropriate cut-off for NYHA I, II, III or IV groups. For both the RAMP and Elecsys results, the median NT-proBNP value was statistically correlated (increasing) with NYHA I, II, III or IV groups, respectively (p<0.0001), with no significant difference between the two methods., Conclusions: The POC Response Biomedical RAMP NT-proBNP assay provides comparable results that measured on the FDA cleared Roche Elecsys central laboratory platform.

Background: The need to rapidly evaluate patients presenting to emergency departments and cardiology services for ruling in and ruling out acute myocardial infarction (AMI) is widely recognized as a clinical challenge. We determined the impact of incorporating point-of-care (POC) cardiac troponin I (cTnI) testing into a cardiology service regarding assay turn around time (TAT), patient length of stay (LOS), financial matrixes and patient outcomes compared to central laboratory cTnI testing., Methods: Patients presenting with symptoms suggestive of acute coronary syndrome (ACS) were enrolled pre-POC (PreCS, n=271) and post-POC (PostCS, n=274). POC cTnI determinations were performed at the bedside on the Dade Behring Stratus CS by nursing staff. Routine cTnI determinations were performed in the central laboratory (Dade Behring Dimension) by laboratory staff. Data were collected and analyzed on each patient per hospital stay by review of electronic medical and financial records. In addition, risk stratification outcomes for all cause death were determined at 30 days and 1 y following baseline sampling based on the 99th percentile cutoff concentrations of <0.1 microg/l for both assays., Results: There was a decrease in time from blood draw to result to healthcare provider (PreCS mean 76 min; PostCS mean 19.5 min; p<0.001) as well as a decrease trend in charge per patient admission (4281 dollars savings) following implementation of POC testing. Total charges per patient admission decreased by 25% PostCS vs. PreCS (17,163 dollars vs. 12,882 dollars); a composite of lower charges for: boarding (-21%), other departments (-58%), pharmacy (-28%), labs (-22%), non-cardiac procedures (-28%), cardiac procedures (-14%). The mean LOS also decreased 8% (p=0.05) from PreCS (2.36 days) to PostCS (2.19 days). cTnI reagents charges to the laboratory were higher for the POC assay, 10.54 dollars, vs. the central lab assay, 3.83 dollars. One year survival was greater in the <0.1 microg/l patients (PreCS 96.2%, PostCS 97.2%) compared to the >0.1 microg/l patients (PreCS 77.7%, PostCS 75.5%); both p<0.001. Kaplan-Meier survival curves showed early separation by 30 days in each group., Conclusions: Our study demonstrates the cost effectiveness and clinical effectiveness of implementation of POC whole blood, cTnI testing for assisting clinicians with diagnostic and risk assessment of ACS patients.

Background: Creatine kinase MB (CK-MB), and cardiac troponin I (cTnI) are important biomarkers for the diagnosis and rule-out of acute myocardial infarction (AMI) of patients who presented to the emergency department (ED) with chest pain. With new rapid ED assessment protocols, there is increasing pressure to produce results with a short turnaround time (TAT), and point-of-care (POC) testing is one alternative for providing fast results., Methods: In a multicenter study, we evaluated the analytical precision, sensitivity and specificity of the RAMP (Response Biomedical) CK-MB and cTnI POC assays and compared results against the Triage (Biosite) POC and the Dimension RxL (Dade Behring) central-laboratory assays on 365 subjects, including 185 patients suspected of AMI, and determined the normal range on 180 healthy individuals. At one site, the clinical sensitivity and specificity were estimated in 121 patients and healthy subjects with AMI using the European Society of Cardiology (ESC)/American College of Cardiology (ACC) definition of AMI. Results from healthy individuals and those with ST elevation and non-ST elevation AMI were included in a receiver operating characteristic (ROC) curve analysis., Results: Intra- and total imprecision ranged from 7.2% to 11.4% for cTnI at 0.22, 1 and 5 ng/ml and 4.8% to 8.6% for CK-MB at 7, 14 and 25 ng/ml. The upper limit of linearity was 32 ng/ml with an average recovery of 105% for cTnI and 80 ng/ml with a 106% recovery for CK-MB. The lower limit of detection was 0.03 ng/ml (10% coefficient of variance [CV] = 0.21 ng/ml) for cTnI and 0.32 ng/ml for CK-MB. The upper reference limit (normal range) was < 0.03 ng/ml for cTnI and 0-3.7 ng/ml for CK-MB. Analytical correlation against Dimension RxL were RAMP=(0.456 x RxL) + 0.11 (r = 0.988, n = 364) for cTnI and RAMP=(0.966 x RxL) + 0.60 (r = 0.986, n = 363) for CK-MB and against Triage, RAMP=(0.626 x Triage) + 0.164 (r = 0.969, n = 364) for cTnI and RAMP=(0.845 x RxL) - 0.495 (r = 0.952, n = 363) for CK-MB. On 39 AMI and 67 non-AMI patients, the clinical sensitivity, specificity and diagnostic efficiency of the cTnI and CK-MB RAMP assays were not significantly different from predicate assays., Conclusions: The RAMP cardiac marker assays are alternatives to other FDA-cleared central laboratory and POC testing devices.

Background: This study determines the analytical characteristics of the i-STAT cardiac troponin I assay (cTnI; i-STAT, Princeton, NJ), a 10-min POC assay, designed to be performed at the bedside., Methods: Three different hospitals participated in a patient specimen and analytical validation study (n=186) for the i-STAT cTnI assay carried out in real time. A total of 186 whole blood specimens (lithium heparin) were collected from patients presenting with symptoms suggestive of acute coronary syndromes (ACS) for correlation studies as well as from 162 healthy subjects for reference interval determination. Factors studied included antibody specificity, detection limit, imprecision, linearity, assay specificity, sample type stability, interferences, reference limit determination and comparison vs. the Dade Stratus CS cTnI assay., Results: Total imprecision (CV) of 10% and 20% were seen at 0.09 and 0.07 microg/l, respectively. The detection limit was 0.02 microg/l. The 99th percentile reference limit was 0.08 microg/l. The assay was not affected by common interferents. An equimolar response within 5% was found for reduced and phosphorylated forms of TIC and IC complexes. Regression analysis for the i-STAT cTnI between whole blood and plasma specimens and for whole blood between the i-STAT and Stratus CS cTnI assays demonstrated slopes of 1.06 and 0.89, respectively., Conclusions: The i-STAT cTnI assay is a sensitive and precise monitor of cTnI, poised for point-of-care/near bedside clinical utilization for triage, diagnostics and risk management of acute coronary syndrome patients., (Copyright 2004 Elsevier B.V.)