Roche Diagnostics
Instructions for Use · Version 13.0 211
cobas b 123 POC system 7 Quality control
Evaluating QC measurement results
Evaluating QC measurement results
q
If a parameter is not calibrated, no QC evaluation can take place. If this occurs, calibrate
the parameter and repeat the QC measurement.
The following methods for evaluating QC measurement results are available:
Verifying the ± 2σ range If the current QC result is within the ± 2 range corresponding to the specified target
value range (refer to package text or stored data on the memory chip), the respective
parameter is evaluated as “OK”.
If the current QC result is outside the ± 2 range, the respective parameter is
evaluated as “nOK”.
u Configuring QC rules and consequences (p. 207).
Multirules
The evaluation of QC results is based on the Westgard
(1)
rules and their
interpretation for blood gas analysis
(2)
. The Multirules process was derived from
these rules. It permits early detection of random and systematic errors associated
with the measuring device and its operation.
The aim of using a Multirule evaluation of your QC results is to keep false rejections
low while the error detection rate is kept high.
Within the Multirule evaluation, Rule 1 (2 SD limits) is not the only criteria for
evaluating but it is the precondition for any further evaluation by the other rules. QC
results within the 2 SD limits are in any case ok but a violation of the 2 SD limit is the
precondition to take the other rules into consideration. So, a QC measurement
always has to violate a combination of rules to be evaluated as nOK.
q
The Multirules process can only be applied with a suitable control material.
(1) James O. Westgard. et al: A Multi-Rule Shewhart Chart for Quality Control in Clinical Chemistry.
Clinical Chemistry, Vol. 27, No.3, 1981
(2) Elsa F. Quam BS. Lorene K. Haessig BS. Marlene J. Koch BS: A Comprehensive Statistical Quality
Control Program for Blood Gas Analyzers. Journal of Medical Technology 2:1 January 1985
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