Abbott i-STAT 1, System Manual

Page: 416 / 658

K - 2
Art: 714174-00J Rev. Date: 12-Jul-11
The i-STAT reference range for whole blood listed above is similar to reference ranges derived from serum or
plasma measurements with standard laboratory methods.
The reference range programmed into the analyzer and shown above is intended to be used as a
guide for the interpretation of results. Since reference ranges may vary with demographic factors such as
age, gender and heritage, it is recommended that reference ranges be determined for the population being
tested.
Clinical Significance
Tests for potassium in the blood are important in the diagnosis and treatment of patients suffering from
hypertension, renal failure or impairment, cardiac distress, disorientation, dehydration, nausea and
diarrhea. Some causes of increased values for potassium include renal glomerular disease, adrenocortical
insufficiency, diabetic ketacidosis (DKA), sepsis and in vitro hemolysis. Some causes of decreased values
for potassium include renal tubular disease, hyperaldosteronism, treatment of DKA, hyperinsulinism,
metabolic alkalosis and diuretic therapy.
Performance Characteristics
The typical performance data summarized below was collected in health care facilities by health care
professionals trained in the use of the i-STAT System and comparative methods.
Precision data were collected in multiple sites as follows: Duplicates of each control fluid were tested in the
morning and in the afternoon on five days for a total of 20 replicates. The averaged statistics are presented
below.
Method comparison data were collected using CLSI guideline EP9-A
4
. Venous blood samples were
collected in lithium heparin Vacutainer
®
tubes and analyzed in duplicate on the i-STAT System. A portion
of the specimen was centri fuged and the separated plasma was analyzed in duplicate on comparative
methods within 20 minutes of collection.
Deming regression analysis
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was performed on the first replicate of each sample. In the method comparison
table, n is the number of specimens in the data set, Sxx and Syy refer to estimates of imprecision based
on the duplicates of the comparative and the i-STAT methods respectively, Sy.x is the standard error of the
estimate, and r is the correlation coefficient.*
Method comparisons will vary from site to site due to differences in sample handling, comparative method
calibration and other site specific variables.
Interference studies were based on CLSI guideline EP7.
6
*The usual warning relating to the use of regression analysis is summarized here as a reminder: For any analyte, “if the data is collected over a narrow
range, the estimate of the regression parameters are relatively imprecise and may be biased. Therefore, predictions made from these estimates
may be invalid”.
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The correlation coefficient, r, can be used as a guide to assess the adequacy of the comparative method range in overcoming this
problem. As a guide, the range of data can be considered adequate if r>0.975.
Precision Data (mmol/L or mEq/L)
Aqueous Control
Mean SD %CV
Level 1 2.85 0.038 1.3
Level 3 6.30 0.039 0.6