Hi Pat, A few years ago Peter Chapple and colleagues published a paper (Bone Marrow Transplant 1998 Jul;22(2):125-30) suggesting that if the PB contains 5 or more CD34+ cell per microlitre, then one can expect to collect at least 0.5 x 10e6 CD34+ cells/Kg patient weight, regardless of age sex and other unmentionables. We use the single platform ISHAGE protocol (aka 'Stem-Kit') for all our CD34+ cell enumerations in the auto PBSC transplant program. Typically, a patient will come in after mobilisation and have blood samples drawn in the morning. From one sample, we obtain an absolute leukocyte count from an automated hematology analyser. We stain the other and analyse it (usually) within 35 minutes of collection and report the data back to the apheresis unit. From the same sample tube as we obtain the absolute CD34+ cell count, we also derive the absolute CD45+ cell (leukocyte) count. As an internal check, we compare these numbers. They should be (and almost invariably are) in very close agreement. If we find 5 or more CD34+ cells per microlitre in the PB sample (based of course on counting at least 100 CD34+ cells), the patient is usually sent for collection. If there are fewer than 5, we usually do not collect them. After collection (and sometimes also during collection) we obtain an aliquot of the product, dilute it 1:10 and obtain a wbc from the hematology analyser. This serves two functions: It tells us whether we need to further dilute the sample prior to flow analysis (max wbc should be about 30,000/microlitre). It also allows the comparison of the absolute wbc with the flow CD45+ cell count as above for the PB sample. We perform another absolute CD34+ cell enumeration, and 40 minutes later the data is reported to the apheresis unit. On the basis of these numbers, it is decided whether more collections are needed, or in some cases, how much longer the patient needs to be apheresed, so that sufficient cells can be collected in order to obviate further collections. The routine use of such procedures has greatly reduced the number of 'failed collections', and significantly decreased the average number of collections per patient to obtain our target CD34+ cell dose of 5 x 10e6 viable (pre-cryo) CD34+ cell per Kg. I have attached a couple of graphs showing our correlations between (1) PB and apheresis CD34+ cell numbers, and (2) hematology analyser WBC versus CD45+ cell counts. These data show that if we have 10 CD34+ cells/microlitre in the PB, then we can expect to get about 1 x 10e6 CD34+ cells per Kg in the collection. Our apheresis unit uses a Cobe Spectra running version 4.0 software. Other versions of the software may not give you the same 'mileage'. I hope this helps. Cheers, Rob Sutherland University Health Network Toronto
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