HemoCue WBC DIFF, Operating Manual, Page: 72 / 84

72
Measuring Range
Displayed range for total WBC count: 0.3–30.0 x10 9 /L (300–
30000/mm
3
, 300–30000/µL) Results above the measuring range
will be displayed as HHH. Results below measuring range will be
displayed as LLL.
The differential cell count will be presented when the total white
blood cell count is between 1.0–30.0 x 10
9
/L.
Limit of Detection
Limit of Detection is defined as the lowest amount of analyte that
can be detected with probability.
Limit of Detection has been determined to be 0.3 x 10
9
/L. (CLSI
Document EP17-A) for WBC count.
Limitations of the Method/Procedure
a) The measurement needs to be started no later than 1 minute
after filling the microcuvette.
b) Do not remeasure a filled microcuvette.
c) Mixing samples for an extended period may affect the result.
d) Results above the measuring range will be displayed as
HHH. Results below the measuring range will be displayed
as LLL.
e) Discard sample if clots.
f) For interference studies see chapter Known Interferences .
Specific Performance Characteristics
Linearity
The white blood cell count for the WBC DIFF system has accord-
ing to the FDA Guidance Premarket Notification for Automated
Differential Cell Counters for Immature or Abnormal Blood
Cells, been demonstrated to be linear between 0.3 – 30.0 x 10
9 /L
with a correlation coefficient (r) to 0.999.
Capillary Sampling
When a capillary skin puncture is performed, several
defense systems in the body are activated very quickly.
These defense systems cause an increase in the number
of WBCs in the blood closest to the wound, leading to
greater differences in results from several samples taken
from the same finger stick.