Subject NT-proBNP Cobas e601 Index Number Lab-4011 Section Laboratory Subsection Chemistry Category Departmental Contact Benjamin Michel Last Revised 10/19/2016 References Required document for Laboratory Accreditation by the College of American Pathologists. Applicable To Employees of the Gundersen Health System clinical laboratory. Detail INTENDED USE: Immunoassay for the in vitro quantitative determination of N-terminal pro-brain natriuretic peptide in human serum and plasma. This assay is used as an aid in the diagnosis of individuals suspected of having congestive heart failure. The test is further indicated for the risk stratification of patients with acute coronary syndrome and congestive heart failure. The test may also serve as an aid in the assessment of increased risk of cardiovascular events and mortality in patients at risk for heart failure who have stable coronary artery disease. PRINCIPLE: The Elecsys probnp II assay is based on a sandwich test principle. The assay contains two monoclonal antibodies which recognize epitopes located in the N-terminal part (1-76) of probnp (1-108). Total duration of assay: 18 minutes. 1. 1 st incubation: Antigen in the sample (15 μl), biotinylated monoclonal NT-proBNP-specific antibody and monoclonal NT-proBNP-specific antibody labeled with a ruthenium complex form a sandwich complex. 2. 2 nd incubation: After addition of streptavidin-coated microparticles, the complex becomes bound to the solid phase via interaction of biotin and streptavidin. 3. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell M. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier. 4. Results are determined via a calibration curve. This curve is instrument-specifically generated by a 2-point calibration and a master curve provided via the reagent barcode. CLINICAL SIGNIFICANCE: Left ventricular dysfunction can occur as part of coronary heart disease, arterial hypertension, valvular disease, and primary myocardial disease. If the left ventricular dysfunction remains untreated and is progressive, the potential for mortality is high, e.g., due to sudden cardiac death. Lab-4011 NT-proBNP Cobas e601 Page 1 of 5
Chronic cardiac insufficiency is a clinical syndrome caused by impairment of a cardiac pumping function. Based on the symptoms, the severity of cardiac insufficiency is classified in stages (New York Heart Association classification [NYHA] I-IV). Clinical tests and imaging procedures are used to diagnose left ventricular dysfunction. The significance of natriuretic peptides in the control of cardiovascular system function has been demonstrated. Initial studies reveal that natriuretic peptides can be used for diagnostic clinical problems associated with left ventricular dysfunction. The following natriuretic peptides have been described: atrial natriuretic peptide (ANP), brain natiueretic peptide (BNP), and C-type natriuretic peptide (CNP). ANP and BNP, by means of their natriuretic and diuretic properties, and as antagonists of the reninangiotensin-aldosterone system, influence the electrolyte and fluid balance in an organism. In subjects with left ventricular dysfunction, serum and plasma concentrations of BNP increase as do the concentrations of the biologically inactive prohormone probnp. ProBNP, comprising of 108 amino acids, is secreted mainly by the left ventricle of the heart and, in the process, is cleaved into physiologically active BNP (77-108) and the N-terminal fragment NT-proBNP (1-76). Studies indicate that probnp can be used in the following applications: The concentration of probnp in serum and plasma indicates the prognosis for the left ventricular dysfunction. It is also useful in assigning symptoms to cardiac or non-cardiac causes. The probnp determination helps to identify subjects with left ventricular dysfunction. Changes in probnp concentration can be used to evaluate the success of treatment in patients with left ventricular dysfunction. There are indications that probnp is suitable for use in assessing vascular remodeling, and therefore contributes to the establishment of individualized rehabilitation procedures. The Roche probnp assay contains monoclonal antibodies which recognize epitopes located in the N-terminal part (1-76) of probnp (1-108). SPECIMEN: Serum or lithium heparin plasma collected using standard sampling tubes or tubes containing separating gel. Stability: 3 days at 15-25 C, 6 days at 2-8 C, 24 months at -20 C. Only one freeze/thaw cycle is allowed. Samples containing precipitate must be centrifuged before performing the assay. Samples and controls stabilized with azide cannot be used. Ensure that patient samples, calibrators, and controls are at ambient temperature (15-25 C) before measuring. REAGENTS/MATERIALS: N-terminal pro B-type natriuretic peptide reagent kit, 100 tests the reagent rackpack is labeled as PRO- BNP II. M - Streptavidin-coated microparticles (transparent cap), 6.5 ml: Streptavidin-coated microparticles, 0.72 mg/ml, preservative. R1 - Anti-NT-proBNP-Ab~biotin (gray cap), 9 ml: Biotinylated monoclonal anti-nt-probnp antibody (mouse) 1.1 ug/ml; phosphate buffer: 40 mmol/l, ph 5.8; preservative. R2 - Anti-NP-proBNP-Ab~Ru(bpy) 2 3 + (black cap), 9 ml: Monoclonal anti-nt-probnp antibody (sheep) labeled with ruthenium complex 1.1 ug/ml; phosphate buffer 40 mmol/l, ph 5.8; preservative. Lab-4011 NT-proBNP Cobas e601 Page 2 of 5
Precautions and Warnings: For in vitro diagnostic use. Exercise the normal precautions required for handling all laboratory reagents. Disposal of all waste material should be in accordance with local guidelines. Storage: Store at 2-8 C. Do not freeze. Store the reagent kit upright in order to ensure complete availability of the microparticles during the automatic mixing prior to use. Stability: Unopened at 2-8 C: up to the stated expiration date. Opened at 2-8 C: 12 weeks. On-board the e601: 8 weeks. EQUIPMENT/INSTRUMENTATION: Roche Cobas e601 analyzer. Refer to the operator's manual for operating instructions, maintenance, and troubleshooting. Calibration: This method has been standardized against the Elecsys probnp assay. This in turn was standardized against reference standards by weighing pure synthetic NT-proBNP (1-76) into an equine serum matrix. Every reagent set has a barcoded label containing the specific information for calibration of the particular reagent lot. The predefined master curve is adapted to the analyzer using the relevant CalSet. Calibrators: probnp II CalSet. Store unopened at 2-8 C. Preparation: Ready for use. Mix carefully, avoiding foam formation. Transfer reconstituted calibrators into two sets of labeled snap-cap bottles. One set is used for immediate calibration and the second set is stored frozen. Stability: 3 months at -20 C. Calibration Frequency: Calibration must be performed once per reagent lot using fresh reagent (i.e. not more than 24 hours since the reagent pack was registered on the analyzer). Renewed calibration is recommended as follows: 1. After 84 days when using the same reagent lot. 2. After 7 days when using the same reagent kit on the analyzer. 3. If dictated by quality control results. 4. If necessary after instrument service or repair. QUALITY CONTROL: BioRad Cardiac Markers Plus LT controls, levels 2 and 3 Refer to Lab-4405 Quality Control Criteria for Chemistry for interpretation of QC. Each level of Quality Control should be performed at a minimum: 1. once every twenty-four hours 2. if a new pack of reagent is put in use 3. if a calibration is performed Implementation Lab-4011 NT-proBNP Cobas e601 Page 3 of 5
Resuspension of the microparticles before use and the reading in of the test-specific parameters via the reagent barcode take place automatically. No manual input is necessary. If in exceptional cases the barcode cannot be read, enter the 15-digit sequence of numbers. Bring the cooled reagents to approximately 20 C by allowing them to sit at room temperature for at least 45 minutes. Place on the reagent disk of the analyzer. Avoid the formation of foam. The system automatically regulates the temperature of the reagents and the opening/closing of the bottles. PROCEDURE NOTES: Results are reported to the nearest whole number in pg/ml. AMR (Analytical Measurement Range): 5-35,000 pg/ml Values below 5 are reported as <5 pg/ml. Values above 35,000 are reported as >35,000 pg/ml. CALCULATIONS: The Cobas 6000 system automatically calculates the probnp concentration of each sample. INTERPRETATION: Expected values: Age (Years) Male (pg/ml) Female (pg/ml) Less than 45 Up to 93 Up to 178 45-54 Up to 138 Up to 192 55-64 Up to 177 Up to 226 65-74 Up to 229 Up to 353 Greater than 74 Up to 700 Up to 600 Note: Since ranges vary greatly by age, borderline results are best interpreted by interpolation. A NT-proBNP result from an obese patient should be interpreted with caution. Obesity due to unknown causes can lower NT-proBNP (or BNP) results even in the presence of CHF. LIMITATIONS: Hemolysis: No significant interference up to an H index of 1000 (approximate hemoglobin concentration: 1.0 g/dl). Icterus: No significant interference up to an I index of 25 (approximate total bilirubin concentration: 25 mg/dl). Lipemia: No significant interference up to a triglyceride concentration of 1500 mg/dl. There is poor correlation between the L index (corresponds to turbidity) and triglycerides concentration. However, Gundersen Health System has established a L index of 97 as a lipemia screen for this test. If the L index is above this number, test triglycerides to determine specimen suitability and then ultracentrifuge specimen if necessary. The triglycerides value of the cleared specimen must be below the limit in order to report results. It may be necessary to ultracentrifuge multiple times. See package insert for additional interference and cross-reactivity studies. The results should always be assessed in conjunction with the patient s medical history, clinical examination and other findings. Lab-4011 NT-proBNP Cobas e601 Page 4 of 5
REVIEW AND CHANGES: This document and all attached forms should be reviewed optimally on an annual basis with 2 years as the maximum review date. Review will be done by the Technical Leader, Medical Director or designated person. Changes require retyping document or form and review by the Medical Director. REFERENCES: 1. Roche probnp II package insert 2. Roche probnp II CalSet package insert 3. Roche Cobas 6000 Operator s Manual Lab-4011 NT-proBNP Cobas e601 Page 5 of 5