Searching for a BNP standard: Glycosylated proBNP as a common calibrator enables improved comparability of commercial BNP immunoassays.
BACKGROUND
Circulating B-type natriuretic peptide (BNP) is widely accepted as a diagnostic and risk assessment biomarker of cardiac function. Studies suggest that there are significant differences in measured concentrations among different commercial BNP immunoassays. The purpose of our study was to compare BNP-related proteins to determine a form that could be used as a common calibrator to improve the comparability of commercial BNP immunoassay results.


METHODS
BNP was measured in 40 EDTA-plasma samples from acute and chronic heart failure patients using five commercial BNP assays: Alere Triage, Siemens Centaur XP, Abbott I-STAT, Beckman Access2 and ET Healthcare Pylon. In parallel with internal calibrators from each manufacturer, six preparations containing BNP 1-32 motif a) synthetic BNP, b) recombinant BNP (E. coli), c) recombinant nonglycosylated proBNP (E. coli), d) recombinant His-tagged (N-terminal) nonglycosylated proBNP (E. coli), e) recombinant glycosylated proBNP (HEK cells), and f) recombinant glycosylated proBNP (CHO cells) were also used as external calibrators for each assay.


RESULTS
Using the internal standards provided by manufacturers and for five of six external calibrators, up to 3.6-fold differences (mean 1.9-fold) were observed between BNP immunoassays (mean between-assay CV 24.5-47.2%). A marked reduction of the between-assay variability was achieved, when glycosylated proBNP expressed in HEK cells was used as the common calibrator for all assays (mean between-assay CV 14.8%).


CONCLUSIONS
Our data suggest that recombinant glycosylated proBNP could serve as a common calibrator for BNP immunoassays to reduce between-assay variability and achieve better comparability of BNP concentrations of commercial BNP immunoassays.
HyTest Ltd., Turku, Finland. Electronic address: alexander.semenov@hytest.fi.
Alexander G
AG
Semenov
HyTest Ltd., Turku, Finland.
Natalia N
NN
Tamm
Department of Laboratory Medicine and Pathology, Hennepin County Medical Center and University of Minnesota, Minneapolis, MN, United States; Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, United States.
Fred S
FS
Apple
Department of Laboratory Medicine and Pathology, Hennepin County Medical Center and University of Minnesota, Minneapolis, MN, United States.
Karen M
KM
Schulz
Department of Laboratory Medicine and Pathology, Hennepin County Medical Center and University of Minnesota, Minneapolis, MN, United States.
Sara A
SA
Love
Department of Laboratory Medicine and Pathology, Hennepin County Medical Center and University of Minnesota, Minneapolis, MN, United States.
Ranka
R
Ler
School of Biology, Department of Biochemistry, Moscow State University, Moscow, Russia.
Evgeniya E
EE
Feygina
HyTest Ltd., Turku, Finland; School of Biology, Department of Biochemistry, Moscow State University, Moscow, Russia.
Alexey G
AG
Katrukha
D000818:Animals; D001774:Blood Chemical Analysis / Q000592:standards*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006023:Glycoproteins / Q000097:blood; D057809:HEK293 Cells; D006333:Heart Failure / Q000097:blood / Q000175:diagnosis; D006801:Humans; D007118:Immunoassay / Q000592:standards; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D011498:Protein Precursors / Q000097:blood*; D012015:Reference Standards
D006023:Glycoproteins; D011498:Protein Precursors; D020097:Natriuretic Peptide, Brain
BNP; Glycosylation; Heart failure; Immunoassay; Standardization; proBNP