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CASY TT Operator‘s Guide
7.11 Poor Result Reproducibility
If the reproducibility of the results is poor:
1
+
Check the number of counted cells.
The number of counted cells should be at least 1,000.
+
To reach ideal reproducibility, adjust the dilution or the number of measuring cycles to measure
between 2,000 and 10,000 cells (see chapter
Operation of CASY TT
).
2
If you use automated aggregation correction, the sample must show a clear cut, well separated peak
of viable cells. In addition, the number of counted events (viable cells + aggregates) should be above
2,000.
If this is not possible, manual aggregation correction is recommended. To find the correct setting for
manual aggregation correction:
+
Measure a sample with a clear cut, well separated peak of viable cells, as well as a viability
> 90%, at least 5 times (2,000 – 10,000 cells per measurement).
+
Enter the average of the measured peak volume into the setup as the basis for manual
aggregation correction.
3
If the repeatability of independently prepared replicate samples is poor:
+
Check if the used volume of CASY ton and the cell suspension were pipeted correctly.
+
Change the sample handling procedures in order to standardize sample pre pa ration (timing,
handling of cells, effort to remove cell clusters,
etc.
). See sections
Preparing the Samples
in chapter
Operation of CASY TT
.
Note that the CASY Instrument can only measure the concentration as present in the CASY cup to be
analyzed. The calculation of the cell concentration in the original suspension depends on the cor-
rectness of the dilution factor.
Poor Result Reproducibility
