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Biomedical subjects

J Seghatchian

Publications and source records attributed to J Seghatchian.

At least 19 recordsLinked to original sources
PubMed2002

The quality of MCS+ version C2 double dose platelet concentrate with leucodepletion through a continuous filtration process.

182 full double donations were collected, using 7-9 cycles with an in-house guideline based on donor HCT, and platelet count. 95.6% of donations were within specifications for platelet yield and 100% were leucodepleted. To overcome the potential for red cell spill-over when the platelet peak is too small, automated continuous monitoring of machine performance has been introduced reducing the potential for spill-over. To understand the impact of the continuous exposure of platelets to the filter, the quality of the first and second part of the collection was monitored using a new set of markers for the platelet storage lesion (activation, microvesiculation, cellular injury, complement and response to ADP). The results were equivalent and compared well with routine practice. Our new protocol allows a wide range of donors to be selected and the highest percentage of products to meet the UK specification with consistency. It is recommended that it can be used for double dose platelets with routine SPM.

Blood Platelets↗
PubMed2002

Cytokines as quality indicators of leucoreduced red cell concentrates.

Different types of filters are currently used for leucodepletion of red cell concentrates. These filters meet the specification for leucoreduction (<5 x 10(6) leucocytes/ATD) but the quality of the final product may differ depending on the performance of the filters for effective removal of both leucocytes, platelets and possibly cytokines which are associated with transfusion reactions. We measured the levels of three representative cytokines: IL-8, RANTES and TGF-beta1 in red cell concentrates prior to and subsequent to the filtration procedure on day 1 and after a storage period of 35 days. Low levels of IL-8 (10-24 pg/ml) in the control unfiltered concentrates on day 1 which increased by approximately twofold on storage. Filtration reduced the levels of IL-8 on day 1 and day 35, in filtered concentrates in comparison with their control unfiltered counterparts. Leucoreduced concentrates produced by three different filters showed similar IL-8 levels on day 1 and day 35. However, concentrates prepared using another type of process showed a twofold increase in IL-8 levels on storage in comparison with day 1. None of the concentrates tested contained any detectable RANTES and TGF-beta1 suggesting a minimal platelet content. These results indicate that a combination of IL-8, RANTES and TGF-beta1 are useful quality indicators for validation of leucoreduced red cell preparations.

Biomarkers↗
PubMed2002

Studies on the characterisation of the cause of leucoreduction failures, with particular reference to extra gatal events.

The causes of leucodepletion failure are multifactoral and can be related to haematological variability in blood donors or donation, defective filters, poor specimen handling or ageing, and/or the presence of non-adhering leucocyte/platelets. Since refiltering removes all types of leucocytes, including the populations appearing as extra gated events, we have developed a practical method for refiltering the failed leucodepleted components on standard filters and back-flushing the second filter to assess the nature of the WBC sub-population. In practice, recovered leucocytes from red cell filters and whole blood mainly consist of neutrophils. Those from platelet and plasma filters were mainly lymphocyte with considerable differences depending on the type of leucodepletion process. Atypical leucocytes are often seen in some pre-/post-cellular leucofiltered components. These appear characteristically as small WBC with a lower affinity for filter matrix, or as cell fragment, pinched leucocyte or apoptotic cells. Different reagents in use show variable sensitivity in identifying these extra gatal events. Storage of leucodepleted samples also induces different types of abnormality in leucocyte dot plot. A useful practical approach for characterisation of the nature of leucocyte sub-populations causing failure in leucodepleted components is provided.

Blood Cell Count↗
PubMed2001

Platelet storage lesion and apoptosis: are they related?

The relationship between the platelet storage lesion (PSL) and programmed cell death (apoptosis) is poorly understood. Nevertheless, there is some experimental evidence that platelets contain most of the components of the apoptosis machinery and both the apoptotic process and the PSL lead to platelet activation and microvesiculation with expression of phosphatidyl serine (PS) on the outer layer of cell membrane, a hallmark of all nucleated cells. The PS exposure is believed to contribute to the development of inflammatory or immunomodulation process, to the regulation of haemostatic balance and the ultimate clearance of dead or fragmented cells from the circulation. While there is no doubt that apoptosis, as a form of genetically encoded programmed cell death in nucleated cells, is triggered by several signalling stimuli at the nuclear level, there is some doubt as to whether platelets, as enucleated cells have retained the memory of the "parental" megakaryocytes for apoptosis or whether platelet mitochondrial DNA has a major role in both the apoptotic process and the PSL. The storage lesion occurs during processing and storage subsequent to mechanical trauma, hypoxic conditions or exposure to cold. In this brief report some observational evidence is provided in support of the notion that the PSL and apoptosis may be related to each other, despite the fact that, in contrast to the 'parental' megakarocyte, the platelets appear to survive upon stimulation with a high concentration of protein kinase inhibitors such as staurosporine (STS), in the presence of cycloheximide (CHX) which inhibit protein synthesis. This is a model which is often used to regulate the level of survival signals. The possible relevance of platelet microvesiculation to transfusion practice is briefly discussed.

Apoptosis↗
PubMed2001

Leukoreduction of sickle cell trait blood: an unresolved issue.

With the increasing demand for leukoreduction of blood components and the implementation of universal leukoreduction in several countries, the problems associated with leukocyte filtration of sickle cell trait blood have been revisited. Currently, there is no unified standard practice for sickle cell trait donors. Different blood centers adopt different policies. While some defer these donors from red cell component donation, some do not. Some screen all ethnic African donors for hemoglobin S (Hb S), others do not. Furthermore, there are differences in views of whether sickle cell trait red cells should be considered as equivalent to non-sickle cell trait red cells. Some blood centers do not give red cells from a sickle cell trait donor to the newborn or patients undergoing general anesthesia as a preventative measure. In this presentation, we discuss the epidemiology of the sickle gene, the sickling process, problems associated with leukoreduction of sickle cell trait whole blood and red cells, and some unresolved issues concerning donor referral and the usage of sickle cell trait blood.

Blood Donors↗
PubMed2001

Monitoring universal leucodepletion performance: the current issues within components production and testing.

The UK NBS completed the introduction of universal leucodepletion in November 1999. This involved the implementation of new methods of production, testing and monitoring, the development of which is still ongoing. Whilst important lessons have been learnt, much remains to be achieved in respect of quality improvement through standardisation of procedures, processes and product modifications to improve safety/efficacy of therapeutic blood components. Since the introduction of universal leucodepletion, many changes in component production and testing have occurred. The primary goal of this report is to review the level of standardisation and harmonisation currently achieved for low leucocyte counting within the NBS and discuss remedial actions undertaken to improve the standard of blood component production and quality monitoring and to highlight some of the related issues which are currently being worked on. The following issues are discussed.

Blood Component Removal↗
PubMed2001

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

BACKGROUND: The levels of residual red blood cells (RBC) and platelets (PLT) in WBC-reduced plasma are often below the lower detection limit of automated blood cell counters. This study established a novel flow cytometric method for the enumeration of residual RBC and PLT in plasma. Furthermore, their levels in WBC-reduced plasma prepared by using various filters were investigated. MATERIALS AND METHODS: WBC-reduced plasma was prepared from two sources: (i) filtration of buffy-coat reduced plasma using dock-on Baxter, Pall and Maco Pharma plasma filters; (ii) filtered whole blood using integral Asahi RZ2000, Maco Pharma LST1, NPBI, and Pall WBF2 whole blood filters. Residual RBC and PLT counts were assessed by using a TruCount tube (Becton Dickinson) containing a known number of lyophilized fluorescent beads. RBC and PLT were labelled with dual monoclonal antibodies, anti-CD41-R-phycoerythrin and anti-glycophorin A-fluorescein isothiocyanide, and analyzed by flow cytometer. RESULTS: The flow cytometric method used in this method can detect residual RBC, PLT as well as RBC-MV simultaneously. The sensitivity of the assay was 50 x 10(6) cells/l with the coefficient of variations < or = 10%. Baxter and Maco Pharma plasma filters consistently reduced both RBC, RBC-MV and PLT to below 50 x 10(6/)l. Plasma derived from day 1 RZ2000 filtered whole blood contained PLT below 50 x 10(6) cells/l, whereas day 0 NPBI filtered whole blood showed the highest level of residual PLT. CONCLUSION: A sensitive and accurate method for the detection of low levels RBC, RBC-MV, and PLT was established to measure their levels in WBC-reduced plasma. The procedure is simple and practical for routine quality monitoring of plasma, as well as for setting a new specification for WBC-reduced plasma.

Automation↗
PubMed2001

Bacterial contamination of blood components.

Despite considerable advances in the safety of blood components, transfusion associated bacterial infection (TABI) remains an unresolved problem. As yet there are no perfect preventative, screening and/or detection methodologies for eliminating contaminated units. Until a practical, rapid, cost-effective and logistically acceptable test becomes available, we should be satisfied with the choice of various limited solutions that at least partially improve the bacterial safety of blood components. It is also necessary to establish standardised guidelines and agreed upon systematic procedures for the recognition and reporting of the laboratory and clinical evaluation of adverse reactions in recipients of contaminated blood components.

Bacteremia↗
PubMed2001

What's happening? The quality of methylene blue treated FFP and cryo.

It is currently unclear to what degree methylene blue in combination with removal, of cells from plasma, by filter, can directly influence the loss of active components of plasma and whether the co-precipitation of FVIII/vWf with fibrinogen/fibronectin is affected by combined methylene blue and light treatment (MBLT). These questions are investigated using the Fenwal system. Our results indicate that up to 15% of the FVIII and IX are lost due to exposure of plasma to filters and methylene blue (MB). The illumination leads to a further 10-15% loss of all other major clotting factors. Factor XI appears to be highly sensitive to the MBLT-process, while inhibitors of the coagulation system are less affected. MBLT did not grossly influence the distribution of fVIII/vWf:Ag between cryoprecipitate and cryosupernatant using a paired control/test protocol, although the fVIII/vWf recovery is reduced in MBLT samples. The three commercially available MBLT processes differ in terms of operational aspects. These may have some impact on overall quality/safety and bioequivalency.

Anti-Infective Agents↗