Test Limitations - Abbott i-STAT 1 System Manual

Concentration
Plasma Blood
Sample
A
B
C
A+B
B+C
A+C
A plasma sample was spiked with BNP to a value of approximately 5000 pg/mL and the concentration was
determined by duplicate measurements with i-STAT BNP test cartridges; the result was found to be within
200 pg/mL of the intended target. This sample was subjected to a series of dilutions with fresh, un-spiked
plasma in order to prepare a range of concentrations. The concentration of each sample/dilution was
calculated based on the measured concentration of the initial solution and the dilutions performed. The
diluted samples were then measured in i-STAT BNP test cartridges (N = 6-10). The procedure was repeated
with a whole blood sample. The results of these experiments are summarized in the following table.
Sample
Plasma
Plasma
Plasma
Plasma
Plasma
Plasma
Plasma
Plasma
Whole Blood
Whole Blood
Whole Blood
Whole Blood
Whole Blood
Whole Blood
Whole Blood
Whole Blood

Test Limitations

The frequency of suppressed results is affected by atmospheric pressure.
increase with higher elevations (decreased barometric pressure) and may become persistent if testing is
performed at more than 7500 feet above sea level. Where unavailability of results is unacceptable, i-STAT
recommends having an alternate test method available.
Samples from patients who have been exposed to animals or who have received therapeutic or diagnostic
procedures employing immunoglobulins or reagents derived from immunoglobulins may contain antibodies,
e.g. HAMA or other heterophile antibodies, which may interfere with immunoassays and produce erroneous
results. The generation of potentially interfering antibodies in response to bacterial infections has been
28-34
reported. While this product contains reagents that minimize the effect of these interferents, and QC
28
algorithms designed to detect their effects, the possibility of interference causing erroneous results should
be evaluated carefully in cases where there are inconsistencies in the clinical information.
Rev. Date: 23-May-12
Diluted Concentration
pg/mL)
590
2764
5123
—
—
—
Calculated [BNP]
Dilution
(pg/mL)
1
2
3
4
5 1036
6 2072
7 3107
8 4143
1
2
3
4
5
6 1450
7 3042
8 4056
Art: 716969-00J
% Recovery
(pg/mL)
—
—
—
1570
3992
2734
Measured [BNP]
(pg/mL)
52 57
104 114
259 265
518 560
1002
2277
3384
4222
44 41
88 88
269 287
537 554
725 720
1367
2826
3856
—
—
—
94%
101%
96%
%Recovery
110%
110%
103%
108%
97%
110%
109%
102%
93%
100%
107%
103%
99%
94%
93%
95%
Suppressed result rates may
BNP - 11