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 transfusions are avoidance of volume overload and the immunomodulatory effects of residual white cells (WBCs). This study evaluated a modification of a leukocyte-reduction system (LRS, Spectra, COBE BCT) for apheresis, which collects high-concentration WBC-reduced platelets (HCPs) for in utero transfusion. STUDY DESIGN AND METHODS: The LRS procedure was modified by running the platelet collection pump at specified low flow rates (Q(col)) for the first part of the procedure, collecting HCPs by gently purging them from the LRS chamber into a designated collection bag and then restoring the original LRS procedure settings to collect a second standard apheresis platelet concentrate (PC). Two centers carried out 32 procedures. Platelet yield, residual WBCs, and in vitro platelet function studies were evaluated. RESULTS: Platelet concentrations in 60 mt of HCPs were predictable according to Q(col) (r(2) = 0.735). HCP yields varied from 0.9 to 3.2 x 10(11), depending on the desired final platelet concentrations in 60 mt, with an overall average of 1.92 x 10(11) (n = 32). Apheresis PCs had a mean platelet yield 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 10(11), n = 12) at concentrations of 1.3 x 10(12) per L for single-needle and 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 be less than 1 x 10(6). HCP in vitro characteristics were equivalent to those of apheresis PCs at 24 hours after collection. In vitro performance declined over storage as a function of HCP yield. HCP pH at 22 degrees C was maintained 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 characteristics and could be stored for 1 to 3 days, depending on the total number of platelets collected. CONCLUSION: A standard apheresis PC and an HCP requiring no secondary processing 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.