Abbott CELL-DYN 3200, Руководство оператора системы

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CELL-DYN ® 3200 System Operator’s Manual
11-23
9140181H—October 2001
Section 11 Quality Control
X-B Analysis for RBC
Overview
The red cell indices (MCV, MCH, and MCHC) are known to be stable because the
red cell apparently functions best in a very narrow range of size and hemoglobin
content. Therefore, the body exerts tight physiologic control and will vary the
number of red cells before altering the average volume or hemoglobin
concentration of those red cells. Consequently, the average red cell indices of a
given patient population will vary no more than 0.5 percent from day to day and
even year to year, providing the population does not change.
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The X-B algorithm
provides a means of utilizing this information for quality control on the
CELL-DYN 3200 System.
The X-B algorithm analyzes the indices on the patient samples run through the
instrument in batches of 20. The mean of each batch is compared to a target value,
and a percent deviation is computed and compared to the acceptable limits. This is
similar to comparing the results of a commercial control run to the appropriate
assay value to determine whether the result falls within the 2SD range. If the
percent deviation exceeds acceptable limits, the message:
X-B OUT
is displayed on
the screen.
Establishing the X-B RBC Target Value
A recent study 6 by Dr. Bull collected data from 1,767 hospitals and yielded the
following mean values:
MCV 89.9 fL
MCH 30.5 pg
MCHC 33.9 g/dL
These values confirmed values that Bull had published in an earlier study.
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Consequently, the values shown above can be used as the Target Values to initiate
the X-B analysis program.
Laboratories seeing specialized patient populations (for example, pediatric
hospitals or tumor centers) may need to verify these values due to “abnormal”
patient populations. Target values may be verified by evaluating approximately
500 samples and comparing the X-B means for those samples to the entered target
values.
The CV on 500 samples for each index should be < 1.5%. (Dr. Bull’s study found
CVs from 0.5% to 1.2%. The 1.5% is one-half the allowable ± 3% action limit,
which is acceptable for this confirmatory step.) If the CVs are >1.5%, an additional
500 samples should be evaluated.
Each laboratory should establish its own target value for the RBC indices. It is
suggested that the process be started by using the default values (preset values from
Dr. Bull’s earlier studies) displayed on the X-B SET UP screen or by entering the
values from Dr. Bull’s recent study described above. The 3% action limits may be
used or widened to 5% during the study and tightened to 3% when the Target
Values are confirmed. The default values for the Lower/Upper Limits may also be
used or widened depending on the specimen population analyzed by the laboratory.