I have noticed a problem with carryover on BD instruments, even when running manually. We do mostly stem cell work here, and it's always necessary to run bleach and water before the CD34 tubes, since we experience carryover of the CD33 PE from the previous tube if we don't. It's not inconvenient, but presents a problem with automation using the loader, which may be why we haven't gotten one. Before I moved to HCI, I was using a Calibur with a loader, and noticed similar carryover. I resorted to running manually, and leaving the sample arm open for several seconds between tubes. Pretty easy solution, but it does add time to the run. As far as automated analysis goes, from what I've seen, I much prefer the Coulter MCL. I used that for over 2 years for HIV, and leukemia immunophenotyping with no noticable carryover. It was quite nice to load up 4 or 5 leukemia panels, and then walk away. It sure made it easier to do multiple runs, as I could stain while the first batch was running, and so on. I'd look into the MCL if you're interested in running from a loader. Dax Arguello Huntsman Cancer Institute Flow Cytometry Core Facility Salt Lake City, UT dax.arguello@hci.utah.edu (801) 581-8641 -----Original Message----- From: Richard McFarland PhD, MD [mailto:mcfarland.richard@pathology.swmed.edu] Sent: Monday, September 20, 1999 1:21 PM To: cyto-inbox Subject: Cell carryover on FacsCalibur with loader > > Intermittently, we experience what appears to be cell carryover >from one tube to the next when acquiring on our FacsCalibur with the >automated sample loader attachment. These cells >form small populations which appear to express bizarre antigen combinations >until it is recognized that these are cells from the immediately previous >tube, stained with different antibodies. When a re-stain is performed, >using a new aliquot of the specimen, these cells disappear. When the >contaminated tube is later re-run, however, the cells are still there, >indicating that a portion of the cells from the first tube actually entered >the second tube. We initially suspected that the tube-tube contamination >occurred before they were put on the cytometer, but that is apparently not >the case, as in one case data from all tubes looked normal, with no >contamination, but when the case had to be re-run for an unrelated reason, >one tube was now contaminated with cells from the immediately preceeding >tube, and when it was run a third time, the cells were still there. We >thought there might be a problem with the pump mechanism, but it has been >replaced (by a B-D FSE) without correcting the problem. Has anyone else >ever experienced >this problem? Any ideas what might cause it? Thanks, Richard McFarland UT Southwestern at Dallas
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