Evaluation of the analytical performance characteristics of the Bayer ACS:180 B-type natriuretic peptide (BNP) assay.

BACKGROUND: B-type natriuretic peptide (BNP) is a cardiac hormone that regulates hemodynamic equilibrium and alleviates ventricular stress. In patients with chronic heart failure, BNP levels increase in proportion to the severity of clinical symptoms and degree of decreased left ventricular ejection fraction. BNP has clinical utility in the evaluation, management, and prognosis of patients with heart failure. METHODS: We evaluated the analytical performance characteristics of the BNP immunochemiluminometric assay in the ACS:180 instrument at three hospital laboratory sites. The analytical performance characteristics evaluated included imprecision, sensitivity (minimum detectable concentration, MDC), analytical measurement range (AMR), dilution linearity/recovery, lot-to-lot reagent variation, high-dose hook effect, and comparison against ADVIA Centaur BNP results on patients' EDTA-plasma samples. RESULTS: Total imprecision was <10% coefficient of variation at BNP concentrations of 43-1830 pg/ml; MDC was 6.9 pg/ml; AMR was 6.9-5000 pg/ml; overall recovery of BNP in samples diluted up to 1:10 was 98%; there was no lot-to-lot reagent variation in BNP results and no high-dose hook effect at BNP concentrations up to 100,000 pg/ml; and, ACS:180 results were highly correlated (r=0.996) with Centaur BNP results. CONCLUSIONS: The ACS:180 BNP assay demonstrated excellent analytical performance characteristics and agreement with BNP results obtained using the Centaur instrument.

Analytical and clinical evaluation of the Bayer ADVIA Centaur automated B-type natriuretic peptide assay in patients with heart failure: a multisite study.

BACKGROUND: B-Type natriuretic peptide (BNP) is released from the left ventricle of the heart into the circulation in response to ventricular stretching and volume overload. Increased BNP concentrations are associated with heart failure (HF). METHODS: We evaluated the analytical and clinical performance of the Bayer ADVIA Centaur BNP assay. Studies included precision, analytical correlation (against the Shionogi ShionoRIA and Biosite Triage BNP assays), BNP results for blood collected in plastic tubes containing EDTA vs other collection tubes, high-dose hook effect, detection limits, and interferences. The clinical performance was tested on 2243 blood samples collected from 983 apparently healthy individuals, 538 patients with chronic disease but without HF (renal insufficiency, chronic obstructive pulmonary disease, diabetes, and hypertension), and 722 patients with HF (New York Heart Association classes I-IV). RESULTS: The ADVIA Centaur assay had total imprecision (CV) of 3.4%, 2.9%, and 2.4% at BNP concentrations of 48, 461, and 1768 ng/L, respectively. The Passing-Bablok correlations to the ShionoRIA and Triage were as follows: ADVIA Centaur = 1.11(ShionoRIA) - 1.19 ng/L (r = 0.98); ADVIA Centaur = 0.78(Triage) + 5.89 ng/L (r = 0.92), respectively. Of the different blood collection tubes, only EDTA plastic tubes (with and without the barrier gel) were acceptable. The lower detection limit was 0.5 ng/L, and there were no interferences from common analytes, other neuropeptides, or unusual antibodies. BNP exhibited different reference intervals according to age and gender. BNP concentrations increased progressively as the severity of HF increased. CONCLUSIONS: The ADVIA Centaur is the first commercially available BNP assay for use on an automated immunochemistry platform. This assay has good analytical and clinical performance characteristics for diagnosing HF.

Analytical and clinical evaluation of the Bayer ADVIA Centaur homocysteine assay.

BACKGROUND: Cardiovascular disease (CVD) is the leading cause of death in the United States. Elevations in homocysteine (Hcy) have been associated with increased risk of acute coronary syndrome, stroke and peripheral vascular disease. Increased utilization of Hcy as a risk marker has prompted the need for high throughput methods that are simple to use and analytically accurate and precise. METHODS: We report the performance characteristics of the automated Bayer ADVIA Centaur chemiluminescent Hcy assay. Centaur Hcy is based on a three-step procedure: (1) reduction of Hcy disulfides to free Hcy, (2) enzymatic conversion of free Hcy to S-adenosyl Hcy (SAH) and (3) quantitation of SAH in a competitive immunoassay (labeled anti-SAH antibody: magnetic particles coupled with SAH). RESULTS: Total assay precision ranged from 3.5% to 6.8% at 4.9-62 micromol/Hcy; linearity undiluted from 0 to 65 micromol/l, up to 650 micromol/l with automatic dilution. Method comparisons with fluorescent polarization immunoassay and high-performance liquid chromatography (HPLC) gave linear regression equations with slopes between 0.95 and 1.0. Measurement of Hcy concentrations in apparently healthy populations yielded middle 95th percentile of 9.7 micromol/l, consistent with epidemiologic studies suggesting that 9-10 micromol/l represents the lower threshold of a population at risk of CVD. CONCLUSIONS: The Centaur Hcy assay is a sensitive and precise assay for the measurement of Hcy.

The effect of class-specific protease inhibitors on the stabilization of B-type natriuretic peptide in human plasma.

BACKGROUND: B-type natriuretic peptide (BNP) is a cardiac hormone that regulates hemodynamic equilibrium. In the circulation, its activity is controlled by proteolytic factors. Accurate measurement of BNP in a patient's plasma may be affected by degradation due to proteolysis. OBJECTIVE: We report on the identification and performance of classes of protease inhibitors that stabilize BNP in plasma. DESIGN AND METHODS: Using the Bayer ADVIA Centaur BNP assay, we measured the effect of arginine, serine and/or specific kallikrein protease inhibitors (PIs) on exogenous spiked or endogenous BNP in patient plasma. RESULTS: Compared to controls without inhibitor, all PIs were capable, to varying degrees, of retarding the rate of proteolytic degradation. The kallikrein-specific inhibitor, D-Phe-Phe-Arg-chloromethylketone (PPACK II) was most effective as a single constituent and was able to eliminate BNP degradation in patient samples for up to 6-10 days when stored at 2-8 degrees C. CONCLUSIONS: The stability of BNP was markedly increased in the presence of kallikrein-specific PPACK II and a broad spectrum of serine PIs. Use of these compounds offers a simple method of extending sample handling and storage of plasma samples containing BNP.