Preparation and storage characteristics of white cell-reduced high-concentration platelet concentrates collected by an apheresis system for transfusions in utero

BACKGROUND: Important concerns with regard to in utero platelet transfusion s are avoidance of volume overload and the immunomodulatory effects of resi dual white cells (WBCs). This study evaluated a modification of a leukocyte -reduction system (LRS, Spectra, COBE BCT) for apheresis, which collects hi gh-concentration WBC-reduced platelets (HCPs) for in utero transfusion. STUDY DESIGN AND METHODS: The LRS procedure was modified by running the pla telet collection pump at specified low flow rates (Q(col)) for the first pa rt of the procedure, collecting HCPs by gently purging them from the LRS ch amber into a designated collection bag and then restoring the original LRS procedure settings to collect a second standard apheresis platelet concentr ate (PC). Two centers carried out 32 procedures. Platelet yield, residual W BCs, and in vitro platelet function studies were evaluated. RESULTS: Platelet concentrations in 60 mt of HCPs were predictable accordin g to Q(col) (r(2) = 0.735). HCP yields varied from 0.9 to 3.2 x 10(11), dep ending on the desired final platelet concentrations in 60 mt, with an overa ll average of 1.92 x 10(11) (n = 32). Apheresis PCs had a mean platelet yie ld of 2.9 x 10(11) (1.3-4.4 x 10(11), n = 20) and 3.9 x 10(11) (2.2-5.8 x 1 0(11), n = 12) at concentrations of 1.3 x 10(12) per L for single-needle an d dual- needle procedures, respectively. Median WBC counts were 5.6 x 10(3) for HCPs and 2.0 x 10(4) for apheresis PCs, with >99 percent expected to b e less than 1 x 10(6). HCP in vitro characteristics were equivalent to thos e of apheresis PCs at 24 hours after collection. In vitro performance decli ned over storage as a function of HCP yield. HCP pH at 22 degrees C was mai ntained at a level of >6.2 for more than 3 days for yields greater than or equal to 1.6 x 10(11), less than 2 days for yields 1.6 to 2.2 x 10(11), and less than 24 hours for yields >2.2 x 10(11). HCPs showed good in vitro cha racteristics and could be stored for 1 to 3 days, depending on the total nu mber of platelets collected. CONCLUSION: A standard apheresis PC and an HCP requiring no secondary proce ssing can be collected with the Spectra LRS. The platelet concentration may be determined by clinical need. HCPs meet the requirements for components that are transfused in utero.