Residual red cell and platelet content in WBC-reduced plasma measured by a novel flow cytometric method

Evaluation of urine dipsticks for quality control of residual erythrocytes and leukocytes in leukocyte-depleted donor plasma

Currently used methodologies for quality control of residual leukocytes and erythrocytes in leukocyte-depleted plasma are either expensive or time-consuming. It has been proposed that urine dipsticks could be used as a screening method for residual erythrocytes. The aim was, therefore, to evaluate if urine dipsticks could be used to detect residual erythrocytes and also residual leukocytes in leukocyte-depleted plasma. Dilution series ranging over the decision limits for residual erythrocytes and leukocytes were prepared. Positive, negative and overall agreements, as well as the precision and joint frequency distributions, were calculated for five dipstick analyzers and their corresponding dipsticks. Twenty-four consecutive leukocyte-depleted donor plasma samples were also tested. None of the dipstick analyzers had both a high positive and a high negative agreement. Accordingly, none of the analyzers were able to discriminate between cell concentrations close to the decision limits. The inconsistency count revealed differences in precision between the dipstick analyzers. In the 24 consecutive donor samples, no significant correlation between the dipstick analyzers and the reference methods were found. In conclusion, urine dipsticks are not suitable for quality control of residual leukocytes and erythrocytes in leukocyte-depleted donor plasma.

Evaluation of a routine hematology analyzer for quality control of leukoreduced plasma

BACKGROUND

Quality control of residual white blood cells (WBCs) and red blood cells (RBCs) in leukoreduced plasma is mandatory. Although technological advances have been made, analysis of quality controls using routine hematology analyzers has not generally been introduced. The aim of this study was to evaluate if the routine hematology analyzer Sysmex XN-10, (Sysmex Nordic ApS) could be used for quality control of residual WBCs and RBCs in leukoreduced plasma.

STUDY DESIGN AND METHODS

Linearity, accuracy, and precision were established for two Sysmex XN-10 analyzers using spiked donor plasma. ADAM rWBC (NanoEnTek) and manual counting in the Bürker chamber (NanoEnTek) were reference methods for WBCs and RBCs, respectively. Twenty-five consecutive leukoreduced donor plasma samples were also tested.

RESULTS

For WBCs, the linearity criteria were met for the ADAM rWBC, but not for the Sysmex XN-10 instruments. Precision on both Sysmex XN-10 instruments was accurate only at 6 cells/μL, and accuracy was consistently acceptable only at 5 to 6 cells/μL. The precision and accuracy of the ADAM rWBC were acceptable at 2 to 6 cells/μL. For RBCs, both Sysmex XN-10 instruments and manual counting in the Bürker chamber were linear and fulfilled the precision criteria. Accuracy was acceptable for both Sysmex instruments at 6 to 12 × 10⁹ WBCs/L but fluctuated within the study's measuring range for the Bürker chamber. No false-positive results were seen in the 25 consecutive donor plasma samples tested.

CONCLUSION

For quality control purposes of leukoreduced plasma, the Sysmex XN-10 analyzer is suitable for the enumeration of residual RBCs but not of residual WBCs.

A flow cytometric method for detection and enumeration of low-level, residual red blood cells in platelets and mononuclear cell products

BACKGROUND

Conventional automated cell counters cannot accurately count residual red blood cells (rRBCs) that are often present in various blood products. A two-color flow cytometric method (FC) was validated for detecting and enumerating rRBCs in platelets (PLTs) and mononuclear cell (MNC) products.

STUDY DESIGN AND METHODS

PLT and MNC products for PLTs (CD61-fluorescein isothiocyanate) and rRBC (anti-glycophorin A-phycoerythrin) were double stained, and data were acquired with a flow cytometer. Assay linearity, accuracy, and precision were assessed with a standard-dilution series of rRBCs. This assay was used to determine the rRBCs of apheresis PLTs collected with Trima Accel (Gambro BCT) and MNC products collected with the COBE Spectra (Gambro BCT).

RESULTS

The linear range of this assay in PLT and MNC products is 10 to 2000 RBCs per microL (R2=0.994). FC had a mean intraassay coefficient of variation of 11.8 percent at 34 RBCs per microL. A standard clinical hematology analyzer overestimated rRBCs in MNC products by 1.59x10(5)+/-0.7x10(5) RBCs per microL. Apheresis PLTs had a median of 17.4 RBCs per microL, with 99.0 percent containing fewer than 90.0 RBCs per microL.

CONCLUSIONS

This method for determining rRBCs in blood products is accurate and repeatable with a lower limit of detection adequate to assess currently available blood products. FC should be considered for determining rRBCs in MNC products.

Blood Cell Apoptosis/Necrosis: Some Clinical and Laboratory Aspects

Exposure of phosphatidyl-serine on blood cell membrane surface and microvesiculation as the hallmarks of apoptosis/necrosis were investigated. The effect of leukofiltration on the retention/generation of microvesicules, leukocyte subsets and major biological response modifiers were evaluated in a like study. It is concluded that apoptotic cells potentially contribute to transfusion reactions in donor/recipient-specific ways.

Platelet storage lesion: an update on the impact of various leukoreduction processes on the biological response modifiers

Currently, platelet concentrates are produced either from pooled buffy which are leukoreduced during processing, by various types of WBC removal filters and several apheresis technologies, which are leukocyte-reduced during collection with or without filtration. It is therefore important to define the impact of various leukocyte-removal processes on the acceleration of platelet storage of lesion and cellular apoptosis/necrosis. This overview briefly highlights the effects of exposure to artificial surfaces, during apheresis leukoreduction processes and platelet storage bags on the development of the platelet storage lesion that may contribute to transfusion reactions. The results obtained from three plateletpheresis technologies are compared with data from a "like with like" study on buffy-coat-derived platelet concentrates, using three types of platelet filter/pack assemblies. Emphasis is placed on the combined preparative methods and storage bags on generation/removal of: kallikrein/kinin; activated complement, leukocytes and platelet-derived cytokines and the development of cellular injuries, measured by the release of Annexin V. There was no systematic evidence of significant cellular fragmentation caused by filtration, but the combined preparative methods and storage bags appears to have some impact on the rate of release of soluble HLA. Moreover, large variability was observed between and within groups, in terms of various laboratory markers of biocompatibility and major biological response modifiers, indicating that much still remains to be done on various aspects of quality improvement to fully abrogate platelet concentrates associated transfusion reactions.

The application of a new quantitative assay for the monitoring of integrin-associated protein CD47 on red blood cells during storage and comparison with the expression of CD47 and phosphatidylserine with flow cytometry

BACKGROUND

After the introduction of universal leukoreduction, the role of factors other than white blood cells in red cell (RBC) storage lesion is attracting increasing attention. These include changes in the levels of CD47 and phosphatidylserine (PS) markers on RBCs during storage. The aim of this study was to monitor these changes with both flow cytometry (FACS) and a newly developed quantitative enzyme-linked immunosorbent assay (ELISA).

STUDY DESIGN AND METHODS

A new quantitative ELISA (monoclonal antibody immobilization of RBC antigens [MAIRA]) was developed. The assay yielded consistent linear curves that enabled the measurement of CD47 expression on RBCs. In addition, FACS was used to measure both CD47 expression and PS on RBCs (n = 3 units) during storage (Days 4, 10, 24, and 31).

RESULTS

A significant reduction in CD47 expression was observed both by MAIRA assay and by FACS by Days 24 and 31 (p < 0.01), and the correlation between the two assays was significant (p < 0.01). In addition, a significant increase in PS was observed by the same storage days with FACS (p < 0.01).

CONCLUSION

The MAIRA assay appears to be suitable for the quantitative measurement of RBC markers during storage. Significant changes in CD47 and PS levels were observed during storage, which may have detrimental immunomodulatory and hemostatic effects on the transfused RBCs.

Red cell storage lesion: The potential impact of storage-induced CD47 decline on immunomodulation and the survival of leucofiltered red cells

Red blood cells undergo major biochemical and biomechanical changes during storage that could effect their post transfusion performance. Biochemical effects include changes in 2,3-diphosphoglycerate (2,3-DPG), ATP, and calcium levels, as well as metabolic modulation and release of Annexin V, a cytosolic component of blood cells, as a global marker of cellular injury and fragmentation. Biomechanical changes include alterations in cellular membrane, shape changes, phospholipid content, phospholipid asymmetry, and antigenic markers. Although the extent of these changes under various storage conditions has been well documented, their clinical effects remain unclear. In the current era of universal leucodepletion, the immunomodulatory effects of some essential markers such as CD47 and phosphatidyl serine become the focus of interest as highlighted in this manuscript.

What is happening? Are the current acceptance criteria for therapeutic plasma adequate?

The main objective of this overview is to highlight the impact of new developments in the processing of plasma, on the quality, safety and efficacy fresh frozen plasma (FFP). Based on the currently available information, it is suggested that current guidelines need an urgent review to include more relevant criteria of acceptability for therapeutic plasma. Moreover additional streamlining of FFP production, using selective donor panel, will improve the uniformity of therapeutic plasma and lower the potential risks of transfusion reactions.

Universal leucodepletion: an overview of some unresolved issues and the highlights of lessons learned

Universal leucodepletion (ULD) has been introduced in several countries based on the evidence that selective leucodepletion improves the clinical safety of blood components and based on animal studies that TSE infectivity is 5-7 times higher in the buffy coat than in plasma. Therefore it is perceivable that the removal of the buffy coat, by filtration, removing both leucocytes and platelets, may prove beneficial in reducing the potential risk of transmission of variant CJD by blood components. The implementation of a ULD policy has created some new requirements: Validation/standardisation of various leucodepletion processes to ensure compliance with set specifications. Standardisation/harmonisation of sampling and low leucocyte counting technologies to ensure the interchangeability of results nationally. The establishment of external quality assessment schemes on 'real' leucodepleted products where the cells come in contact with the filter matrix, to monitor the low leucocyte counting performance, nationally. Assessment of filtration-induced generation/retention of major biological response modifiers (BRM), having potential for the development of transfusion reactions. Using these approaches we have identified that, while the overall leucodepletion performance has improved following harmonisation/standardisation of the operational and counting technologies, there are still some unresolved problems and ULD alone may not provide complete protection from some viral transmission such as HTLV and CMV infections or reduction of bacterial sepsis and generation of some BRM. Moreover, ULD has not fully abrogated febrile non-haemolytic transfusion reactions (FNHTR). Therefore the key issue is not the 3-4 log(10) reduction of residual leucocytes but the design of new generation filters or leucodepletion processes with better performance characteristics, to further reduce some specific leucocyte subsets and their fragments as well as reduce the activation of coagulation/complement/kinin and inflammatory systems. Efforts should also be made to reduce the rapid development of apoptotic/necrotic cells and the residual risk associated with plasma, which often contains a vast array of BRM, responsible for residual transfusion reactions. These could only be effectively achieved by working in cooperation with the suppliers of blood component technologies. This overview briefly highlights some of the unresolved issues related to ULD, based on the experience in the UK. Technical details can be found in the reading list provided at the end.