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Appendix G: Correlation Adjustment
The 800 system provides a setup option, Defining Correlation Coefficients, that
you can use to adjust the slope and intercept values to correlate results from an 800
system with results from another analyzer or methodology.
Before changing these values, you must simultaneously analyze a range of samples
on the 800 system and on a reference analyzer. A properly conducted regression
analysis will provide the appropriate correction equation slope and offset values.
NOTE: Changing the correlation coefficients affects the recovery of calibration
verification materials and proficiency survey materials when analyzed as patient
samples. Consult your proficiency survey administrator for detailed instructions on
reporting adjusted results.
Use the following procedure to determine the slope and offset values for the
correction equation.
1. Access the Correlation Coefficients screen from the Menu screen:
a. Select
5 Operating Setup, and press Enter.
b. Select
8 Correlation, and press Enter.
The Correlation Coefficients screen appears.
2. Ensure that the slope values are set to 1.000 and the offset value is set to 0.00
for each analyte that will be correlated to the reference methodology.
3. Press
Exit Menu to return to the Ready screen.
4. Use a large sample population (minimum of 100 samples spanning the entire
analytical and reporting range) to obtain a random distribution of sample
values.
NOTE:ĄĂFailure to include a significant number of results at the extremes of
the concentration ranges will compromise the quality of the correlation.
5. Analyze each of the samples concurrently on both the 800 system and the
reference analyzer. Do not allow more than 3 minutes between paired
analyses. The data collection should take place over several days to allow the
inclusion of normal analytical variability for both methods. It is recommended
that samples be run in duplicate on both the 800 system and the reference
analyzer
6. Remove any statistical outliers beyond ±3SD.
5
Menu Code
8