Purity??

From: Carl-Magnus Hogerkorp (carl-magnus.hogerkorp@molmed.lu.se)
Date: Wed Feb 02 2000 - 05:27:40 EST


Dear all,

How does one define sort purity? Is there any consensus around how to
present purity figures?

To exemplify:
If sorting a CD34+/CD38- "population" of 6% (based on the 34+ of the total
viable cell population) and knowing how the machine works, a population
rather corresponding to the ~25% lowest gets enriched. Within the original
sorting gate approximately 60% of the events fall and the rest will fall
above the sorting gate. These 40% are not something I would define as
impurities since they are a part of the sorted cluster of CD34+/CD38- cells.
How do I define sort purity? Is it 100% of the 25% lowest or 60% of the 6%
lowest.

It becomes pretty obvious that, if wanting to sort these very 6%, the sort
gate should include perhaps the 1% lowest or something in that way. However,
most users of sorted fractions are not aware of the limitations of the
sorter but merely ask for the 6% lowest. This of course is a bit of a
dilemma for the person operating the sorter since there are no simple
algorithm to apply correcting for this phenomenon. How do others deal with
this?


Thanks for your input


Carl-Magnus Högerkorp
Stem Cell Laboratory
University Hospital of Lund
Sweden



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