Appendix – Quality control ABL90 FLEX reference manual
I-4
Control ranges (for manual QC only)
The control ranges are the ranges within which the result of a quality control
measurement should fall in order for the analyzer to be well functioning. Each
package of quality control ampoules is supplied with an insert with control ranges
for all parameters and analyzers which the given quality control system can
evaluate.
As the control ranges determine whether an analyzer is judged to be well
functioning or not, it is imperative that they are founded on well-established
reference methods and certified reference standards, and in-depth knowledge of
the correlation between an analyzer type and the quality control solution.
Blood gas analyzers are developed to analyze whole human blood, and different
types of analyzers will measure identical values (within the specifications). The
blood algorithm of the analyzers ensures this. When quality control solutions,
which are not blood, are measured, the same corrections will be applied to the
quality control result. Therefore, different types of analyzers will measure
differently, and control ranges must be established separately for each type of
analyzer.
The width of the control ranges is determined during the development phase by
measuring on a number of analyzers. The measurements are performed by
different persons, over several days, using different dispensers and with different
lot numbers of calibration solutions – all this to ensure that all natural variations
such as:
person-to-person day-to-day
analyzer-to-analyzer dispenser-to-dispenser
lot-to-lot variation from calibration solutions, etc.
are included in the control ranges.
The following terms are used by Radiometer in connection with control ranges:
Term Explanation At Radiometer
True value The value of a
parameter in a quality
control solution, e.g.
pH, is traceable to a
primary reference
standard.
There is one true value
for each parameter per
lot of a quality control
solution.
The true value of a
parameter is analyzer-
independent.
The true value for each parameter
included in the reference ampoules
are determined by the Metrology
Section at Radiometer Medical using
NIST standards or standards
traceable to the Danish primary
laboratory for Electrochemistry
(DPLEC) at the Danish Institute of
Fundamental Metrology (DFM). This
primary laboratory is accredited by
Danish Accreditation.
About control
ranges
Definitions
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