Beckman Coulter COULTER LH 750 System, Reference

Page: 52 / 120

PN 4277248DD
3-20
OPERATION PRINCIPLES
XB ANALYSIS
The LH Workstation calculates and displays the percent difference between each batch mean
and its corresponding preset target value. The percent difference is derived as follows:
MCV
MCH
MCHC
Adjusting Initial XB Target Values
The recommended target values for initial entry are:
MCV 89.5
MCH 30.5
MCHC 34.0
As samples are run and laboratory values established, the recommended target values can be
adjusted to fit your laboratory's population. After 20 XB batches have been analyzed, calculate
the mean and CV% for each of the XB indices. The mean values should not differ from the
target values by more than 3%, and the CV should be less than 1.5%. If the CVs are less than
1.5% and the means are less than 3% different from the target values, use the calculated
means as new target values.
If the CVs are greater than 1.5%, or the mean values are greater than 3% different from the
recommended target values, there may be an instrument or population problem. In this case,
repeat this procedure using the next 20 XB batches. If the indices themselves are stable in a
hospital population, then any deviation from the Target Values and Action Limits may point
to an instrument or reagent problem. These problems would involve the parameters directly
measured by the instrument and used to calculate the red cell indices. Table 3.1 lists the
directly measured parameters that would be involved with out-of-limits XB batch values for
each of the red cell indices.
If the XB indices are still out-of-limits, you should investigate the instrument and reagent
systems associated with the directly-measured parameter(s) as indicated by Table 3.1 and call
your Beckman Coulter Service Representative.
percent diff
MCV Batch Mean
MCV T et Value
= −
⎛
⎝⎜ ⎞
⎠⎟
×
arg
1 100
percent diff
MCH Batch Mean
MCH T et Value
= −
⎛
⎝⎜ ⎞
⎠⎟
×
arg
1 100
percent diff
MCHC Batch
MCHC T et Value
= −
⎛
⎝⎜ ⎞
⎠⎟
×
Mean
arg
1 100