Real-time amplification of glyceraldehyde-3-phosphate dehydrogenase gene for quality control of leukopoor platelets

BACKGROUND

Leukoreduction of blood products is crucial to prevent white blood cell (WBC)-associated complications during transfusion. Of the widely accepted methods for quantifying WBCs in blood components, Nageotte hemocytometry is time-consuming and laborious whereas a specialized instrument is required for flow cytometry. A reliable and affordable method to assess WBC count in blood products is of particular interest.

STUDY DESIGN AND METHODS

Real-time polymerase chain reaction (PCR) of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene was developed for quantifying WBCs in leukopoor platelets (LPPs). After normalization by the cell-free prefiltrated and postfiltrated plasma DNA, the relative copy number of GAPDH gene in the platelet (PLT) concentrate and its corresponding LPPs was calculated according to the equation of 2(-ΔΔCt) of which Ct is defined as the threshold cycle. The percentage and the number of WBCs that remained in LPPs were consequently determined. This method was compared to Nageotte hemocytometry and was validated by using serially diluted PLT concentrate and 10 pairs of PLT concentrate-LPP samples.

RESULTS

Consistent with the removal of WBCs after filtration, the Ct values for the LPP samples were increased when compared to their corresponding PLT concentrate. As revealed by real-time PCR of GAPDH gene, there is a correlation between the calculated and theoretical WBC count in the serially diluted PLT concentrate (correlation coefficient, 0.9532). The WBC counts for the 10 LPP samples were comparable between Nageotte and real-time PCR method and were all below 3.3 × 10(6) WBCs/L.

CONCLUSION

The real-time PCR method we report in this study is applicable for routine quality assurance during leukoreduction process.

Evaluation of a new apheresis system for the collection of leukoreduced single-donor platelets

BACKGROUND

The Fresenius COM.TEC cell separator is a new device for producing white cell concentrates (WBCs) and leukoreduced single-donor platelet concentrates (SDPs) and performing therapeutic cytapheresis and plasmapheresis that might replace the Fresenius systems AS104 and AS.TEC 204. This novel system's performance was evaluated for producing leukoreduced SDPs.

STUDY DESIGN AND METHODS

In an investigational phase, each of 200 donors underwent plateletpheresis with the AS.TEC 204 and the COM.TEC systems. The collection efficiency (CE) and WBC contamination of the different techniques were compared. After some hard- and software modifications, the system was evaluated in an additional 800 procedures in the confirmatory phase.

RESULTS

In the investigational phase, the CE of the COM.TEC device was increased significantly in comparison to the AS.TEC 204 device's CE (by 45 +/- 32% when collecting 1 unit of platelets [PLTs] and 1 unit of fresh-frozen plasma and by 43 +/- 42% when collecting only 1 unit of PLTs). Although all AS.TEC products proved to be leukoreduced, 2 percent of the COM.TEC procedures led to PLT concentrates containing more than 1 x 10(6) WBCs. In the confirmatory phase, all 1300 products from 800 COM.TEC procedures proved to be leukoreduced. Furthermore, the CE increased significantly from 53.5 +/- 4.6 percent in the investigational phase to 55.5 +/- 4.9 percent (p < 0.001) in the confirmatory phase.

CONCLUSIONS

These data suggest that the new COM.TEC system offers a significantly and importantly improved CE in plateletpheresis procedures in comparison to the AS.TEC system. In the final version, the PLT products collected with this system fulfill the most stringent criteria for leukoreduced PLTs. This aim was achieved without additional filtration steps and thus without filtration-related PLT loss.

In vitro and in vivo evaluation of LEUKOSEP HRC-600-C leukoreduction filtration system for red cells

BACKGROUND

Documentation of the benefits of leukoreduction has led to the increased use of this technique and the need for development of efficient and effective techniques for its accomplishment. This study investigated the in vitro properties and in vivo autologous radiolabeled recovery of leukoreduced red cells (RBCs) produced through a leukoreduction filtration system for RBCs (LEUKOSEP HRC-600-C, Hemerus Medical).

STUDY DESIGN AND METHODS

Normal subjects donated 36 units of RBCs that were leukoreduced on Days 0, 3, or 5 through a "hands-off" technique. Biochemical studies were performed before and after filtration and at the end of 42 days of storage. Units leukoreduced on Days 0 or 5 were held until Day 42 and used for autologous radiolabeled return to determine recovery with 51Cr single-label radiolabeling techniques.

RESULTS

Leukoreduction filtration was accomplished in 16.3 +/- 2 minutes on Day 0 at room temperature or 27 to 30 minutes on Days 3 or 5 after refrigeration. Leukoreduction efficiency was 4.6 +/- 0.6 log with a median residual white blood cell (WBC) content of fewer than 3.3 x 10(4) WBCs per unit. RBC recovery was 90 +/- 2 percent. Hemolysis was 0.34 +/- 0.16 percent at the end of 42 days of storage. The in vivo recovery of radiolabeled RBCs 24 hours after autologous return was 80.6 +/- 4.5 percent for RBC units leukoreduced on Days 0 and 5 combined.

CONCLUSION

The LEUKOSEP HRC-600-C WBC reduction filtration system produced leukoreduced RBCs efficiently and effectively with acceptable poststorage biochemical measures and posttransfusion recovery after 42 days of storage.

[Residual leukocyte counting in plasma by a real-time genomic amplification assay]

BACKGROUND

Systematic plasma leukoreduction, which was introduced in France in April 1st 2001, has given rise to more sensitive methods for residual leukocytes counting. The technologies in application at this moment (Nageotte hemocytometers and flow cytometry methods) have been modified by a thirty fold sample concentration prior to analysis, inducing frequent downgrading of the plasma unit. So, in order to improve the detection threshold, we developed a more sensitive assay using "Real-Time Polymerase Chain Reaction" technology.

MATERIALS AND METHODS

Real-time polymerase chain reaction was performed on a highly conserved HLADQalpha1 gene sequence. In order to determine the analytical performances of the method (accuracy, sensitivity, linearity and specificity) serial dilutions series ranging from 10(4) to 1 cells/ml were performed. A total of 18 series were prepared from three leukocyte stock solutions, by 1 in 10 serial dilutions in three plasmas completely devoided of white cells (called negative plasmas). To examine the specificity of the assay two negative controls were analyzed in each run.

RESULTS

a sensitivity of 10 cells/ml (10(4) leukocytes/l) was achieved and the assay was linear between 10 and 10(4) cells/ml. The slope (-3.72) of the average standard curve calculated from all series, showed an amplification yield of 92.85%.

CONCLUSION

we developed a quantitative assay for residual leukocytes in leukodepleted plasma, that agreed with the quality control requirement specifications.

Transfusion of leukoreduced cellular blood components from cytomegalovirus-unscreened donors in allogeneic hematopoietic transplant recipients: analysis of 72 recipients

Leukoreduction of blood components has been considered a safe alternative to screening donors for CMV. The objective of this study is to analyze the effectiveness of bedside leukoreduction in preventing CMV transmission. We retrospectively studied 72 transplant recipients and donors who were CMV-seronegative pairs. All patients were transfused with CMV-unscreened cellular blood products leukoreduced at the bedside using leukoreduction filters. Quality control measures performed monthly in our leukoreduced blood components consistently demonstrated that at least 95% of the units sampled meet the leukoreduction criterion established by the American Association of Blood Banks standards. The CMV status of the recipients and donors was determined before transplantation by the latex agglutination assay. Recipients were observed for at least 100 days after transplantation. CMV cultures of urine, buffy coat, bone marrow, and bronchial washings were done weekly when indicated. CMV antigenemia testing was performed twice weekly: 11 transplant recipients seroconverted after transplantation. One patient was positive for CMV antigenemia 4 months after transplantation, but did not have CMV infection. Two of 61 patients who were not seroconverted were CMV antigenemia positive and did not have CMV infection: leukoreduction of cellular blood products is an efficient method of preventing CMV infection.

The impact of two whole blood inline filters on markers of coagulation, complement and cell activation

BACKGROUND AND OBJECTIVES

There exists a current lack of information about the impact of different inline filters, used for the leucoreduction of whole blood (WB), on the levels of clotting factors and markers of coagulation, complement and cell activation in plasma. Only a few small comparisons of different types of WB inline filters have been published to date.

MATERIALS AND METHODS

This study compared two plasma types of 200 units each. Both study groups were derived from WB, inline-filtered and held for 2 h at 20 degrees between donation and filtration. Then, 200 units (Group A) were filtered using a positively charged polyester filter (Baxter RZ2000) and the other 200 units (Group B) were filtered using an uncharged polyester filter (Fresenius). After filtration, both groups were analysed for fibrinogen, factors V and VIII:C (FV and FVIII:C, respectively), immunoglobulin G (IgG), residual leucocytes and platelets, and markers of coagulation, complement and cell activation. Predonation plasma samples from CPDA1-anticoagulated blood were obtained from 100 different individuals and served as controls.

RESULTS

WB inline filtration did not influence fibrinogen, FV, FVIII:C or IgG levels. Neither filter induced thrombin or fibrin formation. The charged filter caused substantial complement activation and neutrophil elastase and platelet factor 4 release. In contrast, the plasma filtered through the uncharged filter showed markedly lower levels of C3a-desArg, C5a, neutrophil elastase and platelet factor 4, and moderately reduced levels of prothrombin fragments 1+2 and D-dimer, compared with controls.

CONCLUSIONS

Filter type has a significant impact on the quality of plasma derived from WB filtered through inline filtration systems. Some filters produce substantial coagulation and complement activation and cell release, while others appear to reduce the plasma levels of activation markers. The clinical significance of these findings remains to be determined.

Development of white blood cell fragments, during the preparation and storage of platelet concentrates, as measured by using real-time polymerase chain reaction

BACKGROUND AND OBJECTIVES

White blood cell (WBC) fragments may cause human leucocyte antigen (HLA) immunization in recipients. We investigated the occurrence and production of WBC fragments in platelet concentrates (PCs) and plasma units, during storage and filtration, by using real-time polymerase chain reaction (PCR) and flow cytometry.

MATERIALS AND METHODS

To study the occurrence of WBC fragments, 'male' WBCs were spiked into double-filtered 'female' PCs in a concentration series of 0.03-100 WBCs/microl (n = 4 per level). To study the production of WBC fragments, 'male' WBCs were spiked into 'female' plasma units to 4 x 10(9) WBCs/l and stored at room temperature prior to filtration (n = 4 per storage time; t = 0, 24 or 48 h). DNA was measured by both albumin real-time PCR and Y real-time PCR. Intact WBCs were counted by using flow cytometry. The number of WBC fragments was calculated by subtracting cell-free DNA (real-time PCR on supernatant) and intact WBCs (flow cytometry) from the total DNA amount (real-time PCR).

RESULTS

Spiking of 'male' WBCs into 'female' PCs showed that the Y real-time PCR is linear and has a reproducible quantitative range down to 0.03 WBC/microl, but that the albumin-PCR, in unspiked samples, revealed a total of 6-10 WBC equivalents/microl (eq/microl). After centrifugation, half of this was observed as cell-free DNA in the supernatant, suggesting that the remaining DNA is derived from WBC fragments. The number of intact WBCs, amount of cell-free DNA and number of WBC fragments after filtration increased significantly when filtration was delayed for up to 48 h, from 0.1 WBC/microl, 1.3 WBC eq/microl and 0.6 WBC eq/microl at t = 0 h to 25 WBC/microl, 38 WBC eq/microl and 57 WBC eq/microl at t = 48 h, respectively.

CONCLUSIONS

WBC fragments occur in WBC-reduced PCs and increase when products are stored, prior to filtration, up to levels that are equivalent to the amounts of intact WBCs that induce HLA immunization (i.e. > 5 x 10(6)/unit).

Optimizing platelet transfusion therapy

Platelet transfusions are widely used. Prophylactic transfusions are employed in severely thrombocytopenic patients without evidence of bleeding, but no randomized trial data prove the safety or efficacy of this approach. Randomized trials have demonstrated the equivalence of transfusion triggers of 10,000 and 20,000/microl for prophylactic transfusions. The former threshold is potentially safer for the patient, conservative of donor resources and leads to lower costs, with perhaps a slightly greater risk of minor hemorrhage. Randomized trials have demonstrated the equivalence of pheresis or whole blood-derived platelet transfusions. The former present a lower risk for infectious agents, and the latter are less expensive and a more efficient use of limited donor resources. Randomized trials prove that leukoreduced and ABO identical platelet transfusions reduce the risks of HLA alloimmunization and platelet transfusion refractoriness (both leukoreduction and ABO matching), transfusion reactions (leukoreduction) and CMV transmission (leukoreduction). Leukoreduction and ABO matching of platelet transfusions also have been associated in preliminary observational studies with reduced morbidity and mortality in surgical patients and reduced infections in patients with leukemia. These results require further investigation. Future challenges include (1) determining the best approach to bacterial contamination of platelets, whether by detection methods or pathogen inactivation and (2) determining the threshold for prophylactic platelet transfusions in thrombocytopenic patients undergoing surgery or invasive procedures.