Hematology analyzers designed to count platelets in samples of whole blood are used to enumerate the total number of platelets in components prepared for transfusion. This report addresses the issue of variability in platelet counts obtained with different models of hematology analyzers. The influence of a common calibration procedure, involving one level of porcine platelets, on the extent of variability was also evaluated. Identical sets of samples of simulated and apheresis-derived human platelets were counted by multiple laboratories in 3 separate studies. In the first 2 exercises, 7 samples of both porcine platelets and modified goat erythrocytes with targeted platelets counts from 0.2 to 4.0 x 10(12)/L were counted without prior dilution. In both exercises, the samples were counted multiple times after routine calibration using instructions provided by the manufacturers of the various hematology analyzers used. In the second exercise, the samples were recounted after the hematology analyzers were recalibrated with a common calibrant consisting of porcine platelets at a targeted concentration of 0.5 x 10(12)/L. In the first and second exercises, 20 and 18 hematology analyzers were used, respectively. In the third exercise, 6 samples prepared from a single unit of apheresis platelets with targeted counts from 0.2 to 1.64 x 10(12)/L were shipped by an overnight courier and counted in triplicate on the day of arrival. Eleven hematology analyzers were used. The influence of recalibration was evaluated statistically by using the 95% prediction interval for the mean of a future set of observations. The platelet counts measured with a specific type of hematology analyzer provided the data to calculate the 95% prediction interval. With routine calibration, a wide variability in platelet counts was observed with all levels of both simulated and apheresis-derived human platelets. For example, with porcine platelets at a targeted level of 0.4 x 10 (12)/L, the platelet counts ranged from 0.31 to 0.47 x 10(12)/L. Recalibration reduced the extent of variability observed with all levels of simulated and apheresis-derived human platelets by increasing the observed platelet counts determined with a subset of hematology analyzers that produced platelet counts in the lower portion of the range. With recalibration, the mean platelet counts obtained with most hematology analyzers, especially with samples having targeted platelet levels no greater than 1.0 x 10(12)/L, were within or near the 95% prediction interval determined with the instruments that provided the highest platelet counts with routine calibration. With recalibration, the reproducibility of the platelet counts was considered to be good for all hematology analyzers with all levels of simulated and apheresis-derived human platelets for most of the instruments. The coefficient of variance did not exceed 6%, with most of the values ranging from 1% to 3%. This study therefore found that the platelet counts of platelet concentrates can be markedly influenced by the type of hematology analyzer used. A common calibration procedure designed specifically for the range of platelet counts in platelet products may be beneficial considering that many different hematology analyzers are being used to count platelets.

BACKGROUND : Many countries are implementing universal WBC reduction of blood components Thus, manufacturing procedures must include QC techniques to detect units that fail to meet established standards.

Cytomegalovirus (CMV) may be transmitted by transfusion of whole blood and cellular components processed according to standard processing procedures. A need exists to develop new procedures to remove CMV and other leukocyte-borne viruses from donor blood. Ten patients (AIDS/bone marrow transplants) who were CMV antigenemic (virus subsequently confirmed by isolation), donated 50 mL of venous blood within 24 to 72 hours of the initial antigen detection. Twenty-five-milliliter aliquots of each specimen were passed through Purecell Neo Neonatal Leukocyte Reduction Filters (Pall, East Hills, NY). The remaining 25-mL nonfiltered aliquots, as well as the blood filtrates, were subjected to infectivity endpoint determinations. The Purecell Neo filter effected a 3 to 4 log10 leukocyte reduction. CMV input titers ranged from less than 10 to 7.3 x 10(1) median tissue culture infectious dose (TCID50) per milliliter. CMV was not isolated from any postfiltration effluent (i.e., leukocytes, erythrocytes, or plasma). CMV DNA was not detected by nested polymerase chain reaction in 8 of 10 postfiltrate blood specimens. The Purecell Neo filter was efficacious in eliminating or significantly reducing viral (CMV) load in venous blood.

Quality control of leukocyte-reduced packed red cell units (LRprc) produced in blood facilities must conform to regulatory criteria, which state that units may not contain more than 1 x 10(6) to 5 x 10(6) white blood cells (WBC) per unit. The post-filtration WBC content of a total of n = 386 LRprc units was counted with a Nageotte chamber to model the probability that a unit would not meet the regulatory criteria. The distribution of the residual leukocyte counts is close to a negative binomial distribution (NBD) and is independent of the packed red cell volume filtered. The observed probability that a unit of blood has a residual WBC greater than 5 x 10(6) is 2.6 +/- 2.6 x 10(-3). A power analysis of the two-sample Kolmogorov-Smirnov (KS) test in this application shows that a sample size of 20 is sufficient for determining that the process is in control when an out of control process has a k NBD parameter greater than or equal to that of the in control process. The three out of control processes observed to date appear to have this property. A sample of size 80 may be necessary for confirming that process validation data sets conform to the larger 'reference' database (n = 386) for processes that are out of control in such a way that their k NBD parameter is less than the k parameter of the in control process.

When blood (plasma) contacts certain foreign surfaces, factor XII can activate and trigger a series of reactions leading to cleavage of kininogens with subsequent release of bradykinin. In this study, we investigated two different widely used leukocyte removal filters, Pall PXL8K (A) and Asahi PLS-5A (B), to test whether clinically significant contact activation occurred during leukodepletion of platelet-rich plasma (PRP). Kininogens were measured by particle concentration fluorescence immunoassay (PCFIA), which can detect cleavage of high and low molecular weight kininogens (HK and LK), the parent molecules of bradykinin, to determine if contact activation had occurred. A slight, nonsignificant decrease in HK and LK was observed with filter A after the first 5 mL was filtered that returned to prefiltration levels by the end of the filtration. Specific TotK (the combined measurement of HK and LK heavy chains divided by plasma protein concentration) showed a small, significant decrease with filter A after the first 5 mL of platelet concentrates was filtered that returned to prefiltration levels by the end of the filtration. There were no significant increases or decreases in the cleaved kininogen index (CKI), an index of HK proteolytic activation or HK and LK destruction (with release of bradykinin). These data suggest that small amounts of both HK and LK initially adsorb to filter A and then desorb, primarily intact. These data also indicate that no significant contact activation, as measured by PCFIA, occurs during leukodepletion of platelet concentrates with either filter A or B.