PubMed Health⌕ Search

Biomedical subjects

Jerard Seghatchian

Publications and source records attributed to Jerard Seghatchian.

28 records · Page 2Linked to original sources
PubMed2004

Variables determining blockage of WBC-depleting filters by Hb sickle cell trait donations.

BACKGROUND: Sickle cell trait donations can block leukodepletion (LD) filters or fail to LD, but the variables affecting blockage are unclear. STUDY DESIGN AND METHODS: To identify critical variables for further study, the relationship was investigated between filter blockage and donor characteristics, processing conditions, PLT and coagulation system activation, and microvesicle formation in donations with (n = 63) and without (n = 40) sickle trait. With eight filter types whole blood was LD either at ambient temperature on Day 0 or after overnight 4 degrees C hold. Markers of PLT activation (CD62P and CD63 expression and soluble CD62P) and coagulation activation (activated FXII and prothrombin fragment 1 + 2 [F1 + 2]), RBC microvesicles, blood gases, and residual WBCs were measured. RESULTS: All Day 0 filtrations blocked (n = 7). On Day 1, no filter tested was 100 percent successful, with most achieving an approximate 50 percent success rate. Two filters blocked consistently and an additional filter did not block, but resulted in 50 percent of units with high residual WBC counts (30 x 10(6)-394 x 10(6)/unit). Day 1 filtration was not improved if performed at 4 degrees C. Donor RBC variables and prefiltration measures varied little between blocked and successful filtrations except pO2, where 9 of 17 blockages had a pO2 of less than 5.0 kPa, compared with 0 of 13 completed filtrations. F1 + 2 levels increased after filtration in sickle trait units, a consequence of slow flow rate. CONCLUSION: Filter blockage in sickle trait donors cannot be predicted by donor characteristics or filter type and is not related to PLT or coagulation activation, but can be reduced by storing units at 4 degrees C before filtration.

Blood Banking↗
PubMed2003

Quality of platelet concentrates derived by platelet rich plasma, buffy coat and Apheresis.

Platelets derived from platelet rich plasma, buffy coat and Apheresis technologies differ in terms of in vitro functional activity, aggregation states and storage characteristics, as measured by automated cell counters, and pH assessment. This may be related to either differences in the subpopulation of platelets and leucocytes recovered or the processing/storage induced cellular damage. Some types of methodologies, such as BC derived-PC, appear to have a higher rate of bacterial contamination.

Blood Component Removal↗
PubMed2003

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.

Cytokines↗
PubMed2003

Elevated FXIIIA and serine proteases upon filtration of platelet concentrate on negatively charged filters: comparison with other established haemostatic markers of platelet activation and storage lesion.

Tests for the assessment of the platelet storage lesion are still evolving. To be of clinical value, they should reflect one of the physiological functions of platelets and should be simple, practical and fit in to the transfusion laboratory setting. In this respect, FXIIIA, Annexin V, vWF and glycocalicin (GC), measured by the established ELISA technology, are of particular relevance, as their roles in the maintenance of haemostatic balance are fully established and they can be released or cleaved upon platelet activation/injury/microvesiculation. The usefulness of these haemostatic markers for in process validation/process qualification, in particular subsequent to harsh procedures and when blood components come in contact with various artificial surfaces, is established and compared with a practical test for routine quality monitoring of platelet functional activity and aggregation states test.

Annexin A5↗
PubMed2002

Validation of different enrichment strategies for analysis of leucocyte sub-populations: development and application of a new approach, based on leucofiltration.

Characterisation of the nature of leucodepletion failure, based on the analysis of leucocyte sub-populations, is an essential task for continual improvement in the clinical safety of blood components and for the selection of a safe and appropriate leucodepletion process. Such information is also critical for improving the quality of filters through an understanding of the mechanism of leucocyte removal filters. Unfortunately, the residual leucocytes of filtered blood components are around the sensitivity of current leucocyte-counting technologies, hence a need for an enrichment process. This preliminary report deals with the merits of various WBC enrichment strategies for the analysis of WBC sub-population subsets. A new procedure, based on refiltering and backflushing the content, with up to 30-fold enrichment, is described. This one-step procedure has the advantage of concentrating both native and atypical leucocytes seen in blood components. The latter may account for lack of interchangeability of results obtained by various counting methods.

Blood Component Removal↗
PubMed2002

A national quality assessment scheme for counting residual leucocytes in unfixed leucodepleted products: the effect of standardisation and 48 hour storage.

BACKGROUND: WBC counting, an essential part of quality monitoring of WBC-reduced blood components, is carried out logistically within 48-72 h of collection. The between-laboratory variability and effects of 24-48 h storage were investigated using three major counting technologies. STUDY DESIGN AND METHODS: Samples of RBC and platelets with WBC in the range 0-50/microl were transported by courier. WBC counting was performed on days 1 and 2, by IMAGN 2000, flow cytometry and Nageotte, initially using local protocols and then using a national flow protocol. Up to 15 laboratories participated in each exercise. RESULTS: For "real failed leucodepleted" red cell products, higher levels of variability were observed for flow and Nageotte, as compared to IMAGN. For spiked RBC samples at critical decision making point (3-20 WBC/microl), between-laboratory the coefficients of variation (CVs) were low for IMAGN and were the highest for Nageotte. Flow cytometry CVs were generally high but improved subsequent to standardisation of sampling and the gating strategy. A similar pattern in the variability of results was observed for platelet concentrates. Sign tests using all samples (carried out for each method in each exercise; 25 in total) demonstrated no overall tendency for larger WBC counts to be recorded on day 1 when compared to day 2, although this difference was significant (p < 0.001) in certain cases depending on the nature of the spiked product. CONCLUSIONS: We conclude that while a good performance is achieved using validated automated technologies for low residual leucocyte counting, the unification of reagents and standardisation of sampling and gating strategies are essential in obtaining interchangeable results. Unfixed RBC and platelet samples can generally be stored for 48 h before WBC counting.

Blood Banks↗
PubMed2002

A platelet quality assessment scheme for comparing the performance of quality monitoring laboratories in the UK National Blood Service.

This exercise focused on performance of NBS quality monitoring establishments with respect to enumeration of low leucocyte and other quality indexes of platelet concentration. Paired identical leucodepleted platelet samples, spiked with WBC (20 cells/microl) in 'vacuette' or 'pouch' were assessed by participants (n = 20) on days 1, 2 and 5. For low WBC counting, all laboratories gave estimates within acceptable range (+/-25%) and good agreement between storage and assay methods was observed on days 1 and 2. Day 5 results showed greater variability. Under improved performance criteria (+/-15%), only one laboratory under-estimated at days 1 and 2. Similarly, other parameters demonstrated good agreement between storage methods on days 1 and 2. At day 5, mean results were often significantly different to previous days. Improved performance target (+/-15%) will allow identification of non-conformers.

Blood Banks↗
PubMed2002

Red cell storage lesion assessed by the levels of potassium, haemoglobin and Annexin V in supernatants.

The conventional and a new marker of global cellular lesion (Annexin V) are used to assess the processing/storage-induced changes in four types of RBC and filtered blood at 4 degrees and 22 degrees C, stored for a period of 35 days, in multi-satellite packs. It appears that mechanical trauma and presence of leucocytes and residual platelets have potential to increase levels of all markers of storage lesion, but to a variable extend. We have also provided new evidence that multi-satellite packs can be safely used for up to 35 days for small volume transfusion to sick premature infants, in a well-managed system by administering several transfusions from the same donation, hence reducing donor exposure.

Annexin A5↗