Quantitating CD34 antigen-positive (CD34+) cells by flow cytometry is a preferred method for assessing the graft adequacy of peripheral blood stem cell (PBSC) collections. It has been reported that the CD34+ population, however, differs among several counting methods depending on the protocol used. Here, we analyzed a total of 131 samples of peripheral blood (n=75), PBSC (n=40) and frozen-thawed PBSC (n=16) for %CD34+ cells and the absolute number of CD34+ cells using single-platform and two-platform protocols with the Cytomics FC500 and Facs Calibur.
%CD34+ cells showed high correlation coefficients (R²=0.980 for peripheral blood, 0.979 for PBSC, and 0.796 for frozen-thawed PBSC) between the Cytomics FC500 and Facs Calibur, and the absolute number of CD34+ cells did not differ between the two machines. For PBSC and frozen-thawed PBSC samples, the absolute number of CD34+ cells correlated well between the single-platform and two-platform methods using the Cytomics FC500 and Facs Calibur. The number of CD34+ cells in peripheral blood detected by the two flow cytometers was, however, higher (Cytomics FC500 : p=0.005, Facs Calibur : p=0.0004) by the two-platform than the single-platform method.
These results show that results for CD34+ cell numbers using the Cytomics FC500 are similar to those with the Facs Calibur when the single-platform method is used. Further, the variation in CD34+ cell count among operators was dependant on errors attributed to pipetting at the dilution of samples or at the addition of beads for CD34+ cell assay. The degree of error attributed to pipetting during dilution with the two-platform and single-platform methods was not significantly different.
Variation in CD34+ cell counts can be reduced by using a single-platform technique in accordance with the International Society of Haematotherapy and Graft Engineering guidelines.

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Viral infection in the post-transfusion period is not always the result of the transfusion, especially if the patient has occult hepatitis B virus (HBV) infection. The look-back study using stored specimens of patients and blood donors is an effective way of confirming whether the infection occurred through transfusion or reactivation. We experienced a case of HBV reactivation in a multi-transfused patient after chemotherapy and peripheral blood stem cell transplantation (PBSCT), which could be confirmed by testing HBV markers with stored specimens both from the patient and blood donors.
A female patient with multiple myeloma in her 50s received intensive chemotherapy and autologous stem cell transplantation. Between Sep 2003 and Oct 2004, she received 305 units of platelet concentrates derived from 19 donors and 20 units of red cell concentrates derived from 15 donors.
One year after this intensive treatment, HBV was detected in her serum for the first time. Since she was HBsAg-negative at pretransfusion (August 2002), HBV transmission by transfusion was suspected. A pretransfusion specimen in September 2003 and 9 consecutive posttransfusion specimens were HBsAg (-), HBsAb (+), HBcAb (+) and HBV-DNA (-). All the stored specimens of the blood donors were negative for HBV-DNA. HBsAb reactivities of her specimens tended to decline and finally became undetectable in September 2005. Thus, it is highly likely that she had occult HBV infection in the pre-transfusion period and that her HBV was reactivated, probably by the chemotherapy and/or PBSCT.

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[in Japanese]

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