BNP - 10 Art: 716969-00J Rev. Date: 23-May-12
Equivalence of Whole Blood and Plasma (x-axis)
Plasma([BNP]<5000pg/mL) Plasma([BNP]<1000pg/mL)
N 49 36
Mean (pg/mL) 776 146
Sxx (pg/mL) 122.0 18.5
Syy (pg/mL) 98.1 16.5
Slope 0.946 1.01
Intercept 50.2 -0.2
Sy.x 107.3 28.3
Xmin 0 0
Xmax 4173 922
Correlation,r 0.997 0.996
Analytical Sensitivity
The limit of blank (commonly termed analytical sensitivity) was estimated at 14 pg/mL by calculating two
times the total imprecision determined using a BNP-depleted plasma material (measured to be <5 pg/mL
BNP) over a 20-day imprecision study using three separate lots of BNP cartridges and 6 i-STAT 1 analyzers.
Analytical Specificity
The BNP method is specific for the B-type natriuretic peptide. The following muscle proteins were tested
at both 1000 pg/mL and 20000 pg/mL concentrations and found to have no detectable crossreactivity for
BNP: ANP, CNP, and N-terminal pro-BNP.
Recovery
The dilution linearity of the i-STAT BNP test was investigated using EDTA whole blood and plasma samples
derived from 3 separate donors. For each donor, the original BNP negative sample and a BNP spiked
sample were prepared. This process yielded three BNP positive whole blood samples that were then
assayed in duplicate for each of 3 separate i-STAT BNP cartridge lots. These whole blood samples were
then diluted using an equal mass of the original unspiked whole blood and assayed in duplicate. From this
whole blood data, the BNP recovery was calculated.
Whole Blood
Sample
Concentration
(pg/mL)
Diluted Concentration
(pg/mL)
% Recovery
A 590 312 106%
B 2765 1429 103%
C 5123 2803 109%
The plasma derived from these three donors was combined in all pairwise combinations in equal volumes.
These combinations were then assayed in duplicate for each of 3 separate i-STAT BNP cartridge lots. The
BNP recovery for each pair was calculated using the average of the 6 results.
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