Re: Cell Surface Receptor Number
Bruce H. Davis, M.D. (bdavis@beaumont.edu)
Sun, 31 Aug 1997 14:06:51 -0400
I felt some defense of using beads for calibration of quantitative
antigen density measurement is in order. I agree with what was so
succinctly written by Bob Ashcroft and Deb Bergland regarding the
assumptions inhererent in deriving an accurate or true quantitation of
molecules/cell using bead standards. Additional problematic issues
exist for the cell surface vs. total cellular measurements of those
molecules that are associated with cell activation related changes, such
as CD11b in neutrophils or CD62P in platelets. However, the methodology
in most situations does allow for relative simplicity and excellent
precision in quantitative cytometric measurements, typically with CVs of
<5% in replicate samples. Thus, although the the quantitative
measurement may not be absolute truth, the results can be derived both
practically and precise in a manner that is highly correlated with a
cell-associated molecular density. This assay performance makes it
highly useful for both research and clinical applications (laboratory
medicine is full of examples of assays where the normal range evolve
with technologic improvements) of quantitative cytometry (flow and
image). So from my perspective, I see an increasing use of bead
calibration for quantitative cytometry, particularly if both users and
vendors of such products acknowledge their limitations and define
conditions for optimized useage. I am optimistic that the current
world-wide efforts towards concensus use of bead standards will provide
potential users wth further improvement of this technique and better
commercial products.
Bruce H. Davis, M.D.
Wm Beaumont Hospital
Royal Oak, MI USA