BNP - 8 Art: 716969-00J Rev. Date: 23-May-12
The i-STAT BNP Calibrators are traceable to an internal reference standard that has been prepared
gravimetrically with synthetic BNP. The internal reference standard underwent a one-time value assignment
to align with the ARCHITECT BNP assay with a decision threshold of 100 pg/mL.
An age-matched analysis of the heart failure and non-heart failure populations was performed based on the
data published by the American Heart Association in the 2000 Heart and Stroke Statistical Update
24
and
according to the age structure of the United States population.
25
The age distributions in the intended use
population are approximately as follows: individuals less than 45 years old comprise 9%, individuals 45-54
years old comprise 11%, individuals 55-64 years old comprise 22%, individuals 65-74 years old comprise
26%, and individuals 75 years and older comprise 32%. The resulting combined AUC is 0.87 (0.85 to 0.90,
95% CI).
The clinical sensitivity and specificity using a decision threshold of 100 pg/mL is presented in the following
table.*
Males (Age Group)
All
<45
Years
45-54
Years
55-64
Years
65-74
Years
75+
Years
Sensitivity 71.0%
(328/462)
47.1%
(8/17)
57.1%
(24/42)
57.3%
(51/89)
70.6%
(115/163)
86.1%
(130/151)
95% Confidence Interval 66.6 to
75.1%
23.0 to
72.2%
41.0 to
72.3%
46.4 to
67.7%
62.9 to
77.4%
79.5 to
91.2%
Specificity 94.8%
(403/425)
97.2%
(104/107)
100.0%
(71/71)
97.9%
(92/94)
88.7%
(102/115)
89.5%
(34/38)
95% Confidence Interval 92.3 to
96.7%
92.0 to
99.4%
94.9 to
100.0%
92.5 to
99.7%
81.5 to
93.8%
75.2 to
97.1%
Females (Age Group)
All
<45
Years
45-54
Years
55-64
Years
65-74
Years
75+
Years
Sensitivity
80.5%
(186/231)
44.4%
(4/9)
73.3%
(11/15)
50.0%
(13/26)
80.6%
(58/72)
91.7%
(100/109)
95% Confidence Interval
74.8 to
85.4%
13.7 to
78.8%
44.9 to
92.2%
29.9 to
70.1%
69.5 to
88.9%
84.9 to
96.2%
Specificity
88.4%
(411/465)
95.9%
(94/98)
90.7%
(68/75)
89.6%
(69.77)
85.7%
(114/133)
80.5%
(66/82)
95% Confidence Interval
85.1 to
91.2%
89.9 to
98.9%
81.7 to
96.2%
80.6 to
95.4%
78.6 to
91.2%
70.3 to
88.4%
* Representative data, results in individual laboratories may vary from these data.
Performance Characteristics
Precision data were collected as follows: Duplicates of each control were tested daily for a period of
20 days for each of 3 lots of cartridges, resulting in a total of 434 replicates. The average statistics are
presented below.
Whole blood imprecision data were collected as follows: whole blood samples from 5 healthy donors
were spiked to low, intermediate and high BNP concentrations affording 15 samples, each of which was
measured in 10 i-STAT BNP cartridges from a single cartridge lot; three lots of cartridges were employed.
The mean within-sample BNP concentration ranged from 84 – 3925 pg/mL and the within-sample
imprecision (%CV) ranged from 3.4 to 9.4%; the average BNP concentration and imprecision were 1464
pg/mL and 6.5% respectively.
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