Rev. Date: 03-Aug-12 Art: 716675-00L CK-MB - 3
following an MI, in contrast to up to 5 days for cTnI or 10 days for cTnT.
3,4,5,6,7
Clinical studies have also
demonstrated a close relationship between the extent of injury to the myocardium (infarct size) following
MI and increased serum CK-MB mass concentrations.
8
Similarly, significant correlations have been
observed between CK-MB estimated infarct sizing and left ventricular echocardiography.
8
Other conditions involving skeletal muscle damage like accidents, blunt trauma, severe burns, and
extreme exercise or myopathic disorders such as myocarditis that are not secondary to ischemic
coronary artery disease can also lead to skeletal muscle or myocardial injury and have the potential to
cause elevations in the blood concentrations of CK-MB. These conditions should be considered when
interpreting results, and the CK-MB level should be used in conjunction with clinical symptoms, signs,
patient history, and ECG changes.
1,9
Performance Characteristics
Precision data were collected in multiple sites as follows: Duplicates of each control were tested daily
for a period of 20 days for each of three lots of cartridges, resulting in a total of 120 replicates. The
average statistics are presented below.
Method comparison data were collected using CLSI guideline EP9-A2.
10
Venous blood samples were
collected in heparinized evacuated tubes and analyzed in duplicate on the i-STAT System. A portion
of the specimen was centrifuged and the separated plasma was analyzed in duplicate on the i-STAT
System and on the comparative method within 1 hour of collection.
Deming regression analysis
11
was performed on the first replicate of each sample. In the method
comparison table, n is the number of specimens in the first 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 may 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-A.
12
*The usual warning relating to the use of regression analysis is summarized here as a reminder. For any analyte, “if the data is a narrow range, the
estimate of the regression parameters are relatively imprecise and may be biased. Therefore, predictions made from estimates may be invalid”,
10
The
correlation coefficient, r, can be used as a guide to assess the adequacy of the comparative method range in overcoming the problem. As a guide,
the range of data can be considered adequate if r>0.975.
Precision Data (ng/mL)
Plasma Control Mean SD %CV
Level 1 5.9 0.7 11.9
Level 2 25.8 2.7 10.4
Level 3 90.1 9.0 10.0
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