ChemoMetec SCC-100 - Manual (Page 33)

5 Operation of the NucleoCounter
21
5.3.4 External computer
If an external computer with the SomaticView software installed on it is connected, the
results and the recorded fluorescent image can be viewed using the SomaticView
software.
After the measurement is completed the cassette can be safely removed (see section
5.2). Sometimes, however, the complete process described above may be interrupted.
Please familiarize yourself with possible error handling of the NucleoCounter presented
in chapter
7 .
5.4 Result display
Following a successful analysis, the cell density will be displayed on the display screen.
Figure 13 shows an example of results as given on the display of the NucleoCounter
instrument.
SCC
1,234,000/ml
Figure 13. Somatic Cell Count of a milk sample, presented on the display of the
NucleoCounter in cells per ml.
5.4.1 Result presentation
The NucleoCounter presents Somatic Cell Count (SCC) rounded towards the nearest
thousand per ml. Results at 10,000 or less are presented as <10,000/ml and results
above 2,000,000/ml are presented as >2,000,000/ml.
The number of digits presented generally exceeds the number of significant digits,
considering the repeatability of the instrument. The repeatability of the instrument is
largely dominated by the characteristics of counting random events, as described by the
Poisson distribution. According to the Poisson distribution the standard deviation of a
measurement based on the counting of n random events is equal to the square root of
the number of events counted, or s
Poisson
= n .
5.4.2 Precision
Results on the NucleoCounter follow the Poisson distribution closely and since about
1/1000th of a ml of milk is analyzed in each measurement then the number of events
counted is approximately equal to the number of thousand cells per ml, e.g. if the result
is 500,000 cells/ml then about 500 cells have been counted and thus resulting in
corresponding Poisson standard deviation s
Poisson
= 22 500 ≈ or equivalent to about
4.5%. The following table gives a list of SCC and the corresponding s
Poisson
.