title: The development and application of a high-sensitivity immunoassay for cardiac myosin-binding protein C.
abstract: Cardiac troponins (cTns) are released and cleared slowly after myocardial injury. Cardiac myosin-binding protein C (cMyC) is a similar cardiac-restricted protein that has more rapid release and clearance kinetics. Direct comparisons are hampered by the lack of an assay for cMyC that matches the sensitivity of the contemporary assays for cTnI and cTnT. Using a novel pair of monoclonal antibodies, we generated a sensitive assay for MyC on the Erenna platform (Singulex) and compared serum concentrations with those of cTnI (Abbott) and cTnT (Roche) in stable ambulatory cardiac patients without evidence of acute cardiac injury or significant coronary artery stenoses. The assay for cMyC had a lower limit of detection of 0.4 ng/L, a lower limit of quantification (LLoQ) of 1.2 ng/L (LLoQ at 20% coefficient of variation [CV]) and reasonable recovery (107.1 ± 3.7%; mean ± standard deviation), dilutional linearity (101.0 ± 7.7%), and intraseries precision (CV, 11 ± 3%) and interseries precision (CV, 13 ± 3%). In 360 stable patients, cMyC was quantifiable in 359 patients and compared with cTnT and cTnI measured using contemporary high-sensitivity assays. cMyC concentration (median, 12.2 ng/L; interquartile range [IQR], 7.9-21.2 ng/L) was linearly correlated with those for cTnT (median, <3.0 ng/L; IQR, <3.0-4.9 ng/L; R = 0.56, P < 0.01) and cTnI (median, 2.10 ng/L; IQR, 1.3-4.2 ng/L; R = 0.77, P < 0.01) and showed similar dependencies on age, renal function, and left ventricular function. We have developed a high-sensitivity assay for cMyC. Concentrations of cMyC in clinically stable patients are highly correlated with those of cTnT and cTnI. This high correlation may enable ratiometric comparisons between biomarkers to distinguish clinical instability.
authors.affiliation: King's College London BHF Centre, The Rayne Institute, St Thomas' Hospital, London, UK.
authors.forename: Jack
authors.initials: J
authors.lastname: Marjot
authors.affiliation: Kerckhoff Heart and Thorax Center, Department of Cardiology, Bad Nauheim, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site RheinMain, Bad Nauheim, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Liebetrau
authors.affiliation: Singulex Inc, Alameda, Calif.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Goodson
authors.affiliation: King's College London BHF Centre, The Rayne Institute, St Thomas' Hospital, London, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kaier
authors.affiliation: Institute of Physiological Chemistry, Martin Luther University Halle-Wittenberg, Halle, Germany.
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Weber
authors.affiliation: Singulex Inc, Alameda, Calif.
authors.forename: Peter
authors.initials: P
authors.lastname: Heseltine
authors.affiliation: King's College London BHF Centre, The Rayne Institute, St Thomas' Hospital, London, UK. Electronic address: mike.marber@kcl.ac.uk.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Marber
mesh_terms: D015415:Biomarkers / Q000097:blood*; D002138:Calibration; D002352:Carrier Proteins / Q000097:blood*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D057230:Limit of Detection; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood; D016491:Peripheral Vascular Diseases / Q000097:blood; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood; D020107:Troponin T / Q000097:blood; D000099163:Myosin Binding Protein C
chemical_list: D015415:Biomarkers; D002352:Carrier Proteins; D019210:Troponin I; D020107:Troponin T; D000099163:Myosin Binding Protein C