Abbott i-STAT 1, System Manual

Page: 443 / 658

Rev. Date: 01-Aug-11 Art: 714179-00L
iCa - 3
Method Comparison (mmol/L)
Radiometer ICA1 Nova STAT Profile
n 47 57
Sxx 0.009 0.017
Syy 0.017 0.017
Slope 0.925 0.960
Int’t 0.113 0.062
Sy.x 0.035 0.029
Xmin 0.46 0.53
Xmax 2.05 2.05
r 0.982 0.982
Cartridge Comparison
The performance characteristics of the sensors are equivalent in all cartridge configurations. System
difference analysis was performed on 24 patient samples using i-STAT CHEM8+ and i-STAT CG8+
cartridges. In the 0.46 - 1.23 mmol/L range, the average difference was 0.003.
Factors Affecting Results*
Venous stasis (prolonged tourniquet application) and forearm exercise may increase ionized calcium due to
a decrease in pH caused by localized production of lactic acid
6
. Exposing the sample to air will cause an
increase in pH due to the loss of CO
2
which will decrease ionized calcium.
Heparin binds calcium. Each unit of heparin added per mL of blood will decrease ionized calcium by 0.01
mmol/L.
6
Therefore, the correct ratio of heparin anticoagulant to blood must be achieved during sample
collection. Intravenous injection of 10,000 units of heparin has been shown in adults to cause a significant
decrease of ionized calcium of about 0.03 mmol/L.
6
Use only unheparinized sample transfer devices when
using i-STAT’s aqueous control and calibration verification materials.
Hemodilution of the plasma by more than 20% associated with priming cardiopulmonary bypass pumps,
plasma volume expansion or other fluid administration therapies using certain solutions may cause clinically
significant error on sodium, chloride, ionized calcium and pH results. These errors are associated with
solutions that do not match the ionic characteristics of plasma. To avoid these errors when hemodiluting by
more than 20%, use physiologically balanced multi-electrolyte solutions containing low-mobility anions (e.g.
gluconate) such as Normosol
®
-R (Abbott Laboratories), Plasma-Lyte
®
-A (Baxter Healthcare Corporation),
and Isolyte
®
-S (B Braun Medical) rather than solutions such as normal saline or Ringer’s Lactate.
Test concentrations used were as per the CLSI guidance document,
7
unless otherwise indicated.
The following substances are known to interfere with the i-STAT Ionized Calcium assay:
Substance
Test Concentration
(mmol/L)
Interference
Acetaminophen 1.32
Decreased i-STAT Ionized Calcium results.
See Note below.
Acetylcysteine 10.2
Decreased i-STAT Ionized Calcium results.
See Note below.
Bromide 37.5
Increased i-STAT Ionized Calcium results.
See Note below.
Magnesium 1.0
Increased i-STAT Ionized Calcium results by
approximately 0.04 mmol/L.
Lactate 6.6
Decreased i-STAT Ionized Calcium results by
approximately 0.07 mmol/L.
Salicylate 4.34
Decreased i-STAT Ionized Calcium results.
See Note below.
Salicylate (therapeutic) 0.5
10
Decreased i-STAT Ionized Calcium results by
approximately 0.03 mmol/L. See Note below.