CD34 counting: Partec vs. BD TruCount

Dear Flowers,

Until now we used BD's TruCount tubes on a FACSort  and recently we  
try  shift to a new Partec CyFlow space flow cytometer because of its  
unique "absolute volumetric counting" feature  but we have have very  
interesting (strange)  results.
Using the same samples on the two machines (simply pipetted the  
stained samples from the TruCount tube into the Partec's tube before  
measuring) I have different results. At least in 10 different samples  
there is a 1,3-1,5 factor between the CD34 counts in favour of the  
FACSort.
In the Trucount tubes' manual BD says that not to transfer the beads  
to another tube. May any special coating on the Trucount tube surface  
which is necessary for the proper performance using blood samples ?
Otherwise when I measure the TruCount beads only, diluted in PBS and  
transfered to the Partec tubes I get very accurate bead  
concentrations. The same accuracy could be achieved with Partec's  
calibration beads. These latter results suggest to me that I should  
accept the Partec results instead of the BD's FACSort.
Any ideas ?

Best regards,

Pal Jakso

University of Pecs
Faculty of Medicine
Dept. of Pathology
12. Szigeti str.
H-7643 Pecs, HUNGARY