Storage of red blood cells in a novel polyolefin blood container: a pilot in vitro study.

BACKGROUND AND OBJECTIVES: The present general plasticizer di-2-ethylhexyl-phthalate in polyvinylchloride (PVC) blood bags is only physically dispersed in PVC and will therefore leach into blood components. The objective of this study was to perform a first preliminary red blood cell (RBC) storage evaluation in a new blood bag manufactured of polyolefin without any inclusion of potentially migrating substances. STUDY DESIGN AND METHODS: This is a RBC storage study for 42 days. Blood collection was performed in a polyolefin-based PVC-free blood bag. RBCs were prepared within 8 h. Two different RBC additive solutions were used, either PAGGS-M or PAGGG-M. We weekly measured pH, K+ , glucose, lactate, haemolysis, red cell ATP and 2,3-DPG. RESULTS: RBC storage in PAGGS-M resulted in high haemolysis levels already after 21 days, exceeding the European maximum limit of 0·8%, and low ATP levels by the end of the storage period. With PAGGG-M, haemolysis exceeded 0·8% after 28 days of storage. For additional parameters, the results were comparable to those of previous studies in conventional blood bags. CONCLUSION: This is a first preliminary study of RBC storage in a new type of blood bags. PAGGG-M gave encouraging results except for its inability to prevent increased haemolysis. There will be room for further development of RBC additive solutions to address the haemolysis problems. Plasma should also be tested regarding the stability of coagulation and activation pathway variables. There may also be a potential for future use of the bag for preparation of pooled buffy-coat-derived platelets.

Platelet storage media.

Present platelet storage media often designated platelet additive solutions (PAS) basically contain acetate, citrate and phosphate and recently also potassium and magnesium. However, there seems to be an increasing interest in developing PASs that can be used also after further reduction of residual plasma content below 15-20% plasma. Inclusion of glucose but also calcium and bicarbonate in such solutions have been suggested to improve platelet (PLT) storage, especially when plasma content is reduced to very low levels. Results from a limited number of studies using novel PAS alternatives have been presented during the last years, such as InterSol-G, PAS-5, M-sol, PAS-G and SAS. Most of them are experimental solutions. The combined results presented in those studies suggest that presence of glucose may be necessary during PLT storage, primarily to maintain ATP at acceptable levels. At plasma inclusion below 15-20%, the content of glucose will generally be too low to support PLT metabolism for more than a few days making glucose addition in PAS necessary. Significant effects associated with presence of calcium was observed in PLTs stored in PAS with 5% inclusion but not with 20-35% plasma inclusion, suggesting that the content of plasma could be of importance. Bicarbonate only seems to be of importance for pH regulation, primarily when plasma inclusion is reduced to about 5%. Reduction in rate of glycolysis was observed in some PAS alternatives containing potassium and magnesium but not in others. Differences in pH or in concentrations of the various compounds included in PAS may be possible explanations. Additionally, novel PAS containing glucose, calcium and bicarbonate does not seem to be associated with improved in vitro results as compared to SSP+ or CompoSol when PLTs are stored with 35% plasma inclusion. The results would then also suggest that excess of glucose in novel PAS environment may not be associated with additional positive effects on PLT metabolism. This review is based on the few publications on novel PAS available, and additional studies would be needed in the future.

Effect of transient warming of red blood cells for up to 24 h: in vitro characteristics in CPD/saline-adenine-glucose-mannitol environment.

BACKGROUND AND OBJECTIVES: There are few studies on transient warming of red blood cells (RBCs). Occasional storage outside restricted temperature range often results in destroying of the RBC unit, even after a short period of time due to national guidelines. This study evaluates the in vitro effects associated with such accidental warming on RBCs stored in saline-adenine-glucose-mannitol (SAGM) and prepared within 8 h after blood collection. STUDY DESIGN AND METHODS: This study includes both repeated short-term exposure of RBCs to room temperature for 6 h as wells as warming for either 6, 12, 18 or 24 h after 1 week or after 3 weeks of storage in two separate studies. RBCs were stored for 42 days. We weekly measured pH, K(+) , glucose, lactate, haemolysis, red cell ATP and 2,3-diphosphoglycerate. RESULTS: The lowest individual ATP value observed in any of the groups of warmed units was 2·6 µmol/g haemoglobin. Increased haemolysis in warmed units was noted in two of the studies. None of the individual units exceeded the European maximum limit of 0·8% haemolysis. CONCLUSION: Our results suggest that quality of RBCs after transient warming will be maintained at acceptable levels specified in standards and in previous studies. However, increased haemolysis was observed when transient warming occurred during the second part of the storage period of 6 weeks suggesting that RBCs are more vulnerable to warming by the end of storage.

Coagulation factor content of plasma produced from whole blood stored for 24 hours at ambient temperature: results from an international multicenter BEST Collaborative study.

BACKGROUND: There is increasing international interest in producing components from blood that has been stored at room temperature for 24 hours. The lack of comprehensive data on the quality of plasma produced from blood stored in this way led to this international study. STUDY DESIGN AND METHODS: A total of 128 units of whole blood were pooled in groups of four and split to produce 32 sets of four identical blood units that were processed either within 8 hours of blood collection or after 24-hour storage at 18 to 25°C. RESULTS: Storage of whole blood for 24 hours resulted in a 23% decrease in the activity of Factor (F)VIII, but not significant loss of activity of coagulation factors FV, FVII, FXI, FXII, fibrinogen, antithrombin, or von Willebrand factor. There was a small, but significant decrease in levels of FII, FIX, and FX (all <5%) as well as protein C (6%) and free protein S activity (14%). The ability of plasma to generate thrombin after 24-hour storage as whole blood was unaltered, as assessed by real-time thrombin generation tests as was the rate and strength of clot formation by rotational thombelastometry. Levels of all coagulation factors measured were above 0.50 U/mL in plasma produced from whole blood stored for 24 hours. CONCLUSION: These data show that there is minimal effect of storing whole blood at ambient temperature for 24 hours on the coagulation activity of plasma and that this is an acceptable alternative to producing plasma on the day of blood collection.

In vitro effects on platelets irradiated with short-wave ultraviolet light without any additional photoactive reagent using the THERAFLEX UV-Platelets method.

BACKGROUND: A novel short-wave ultraviolet light (UVC) pathogen reduction technology (THERAFLEX UV-Platelets; MacoPharma, Mouvaux, France) without the need of any additional photoactive reagent has recently been evaluated for various bacteria and virus infectivity assays. The use of UVC alone has on the one hand been shown to reduce pathogens but may, on the other hand, have some impact on the platelet (PLT) quality. The purpose of this study was to determine the potential effects on PLT quality of pathogen inactivation treatment using the novel UVC method for PLT concentrates. STUDY DESIGN AND METHODS: Buffy-coat-derived PLTs suspended in SSP+ were irradiated with UVC light in plastic bags (MacoPharma) made of ethyl vinyl acetate, considered to be highly permeable to UVC light. The UVC-treated (test, n=8) as well as the untreated (reference, n=8) PLT units were stored in PLT storage bags composed of n-butyryl, tri n-hexyl citrate-plasticized polyvinyl chloride (MacoPharma) on a flat bed agitator for in vitro testing during 7 days of storage. RESULTS: No significant difference in PLT counts and lactate dehydrogenase between the groups was detected. During storage, glucose decreased more and lactate increased more in the test units. Statistically significant differences were found for glucose (P<0·01) and lactate (P<0·05) on day 7. ATP levels were higher (P<0·01 from day 5) in the reference units. With exception of day 7 (P<0·01 reference vs. test), hypotonic shock response reactivity was not different between groups. Extent of shape change was lower (P<0·01), and CD62P (P<0·05 day 5) was higher in the test units. CD42b and CD41/61 showed similar trends throughout storage, without any significant difference between the units. pH was maintained at >6·8 (day 7) and swirling remained at the highest level (score = 2) for all units throughout storage. CONCLUSION: Our results suggest that irradiation with UVC light has a slight impact on PLT in vitro quality and appears to be insignificant with regard to current in vitro standards.

Storage of Buffy-coat-derived platelets in additive solutions: in vitro effects on platelets prepared by the novel TACSI system and stored in plastic containers with different gas permeability.

BACKGROUND: The novel TACSI system is designed for automated preparation of platelets (PLTs) from pooled buffy coats (BCs). One TACSI device will handle 6 units at the same time. The aim of our in vitro study is to investigate the effects of using this automated equipment with subsequent storage in two different plastic containers and to compare these results with PLTs prepared by the OrbiSac system. STUDY DESIGN AND METHODS: Buffy-coat-derived PLTs (n=8) were prepared by using the TACSI system, including storage in polyvinyl chloride (PVC)-based plastic containers with di, n-decyl phthalate (DnDP) (TACSI R) and BTHC (TACSI T)-based plasticizers. As a reference, the OrbiSac System was used to prepare PLTs (n=8) with subsequent storage in a PVC plastic container with a citrate-based plasticizer (BTHC). In total, 16 TACSI and eight reference units, supplied by approximately 30% plasma and 70% SSP+, were analysed for various in vitro variables during the 7-day storage period. RESULTS: No significant difference in PLT counts, LDH, mean platelet volume (MPV) and adenosine triphosphate between the groups was detected. Glucose was lower (P<0·05) and lactate was higher (P<0·05) in TACSI R vs. OrbiSac. With exception of day 7 (P<0·05 TACSI R vs. OrbiSac), HSR reactivity were not different between groups. Extent of shape change was lower and CD62P higher in TACSI T when compared with TACSI R and OrbiSac units (P<0·05). pH was maintained at >6·8 (day 7) and swirling remained at the highest level (score=2) for all units throughout storage. CONCLUSION: Platelets prepared by the TACSI system with subsequent storage in two different PVC-based plastic containers were equivalent to reference PLTs with regard to in vitro characteristics during 7 days of storage.

Storage of buffy-coat-derived platelets in additive solutions: in vitro effects on platelets stored in reformulated PAS supplied by a 20% plasma carry-over.

BACKGROUND AND OBJECTIVES: Platelet additive solutions (PAS) have been shown to be suitable for extended platelet (PLT) storage. Depending on the PAS formulation, the percentage of plasma carry-over contributes to success. Improving PLT quality by optimizing the composition of PAS may allow a reduction to be made in the amount of plasma carried over to the final unit. Reducing the proportion of plasma carried over would probably decrease transfusion of unwanted antibodies and make greater amounts of plasma available for other needs. STUDY DESIGN AND METHODS: Platelets from eight pools of 25 buffy coats were aliquoted and prepared for storage in plasma and different PAS units: InterSol and three alternate PAS named PSM1, PSM2 and PSM3. All PAS units were supplied with a 20% plasma carry-over and stored at room temperature with agitation for 9 days with in vitro testing for metabolic, cellular and activation parameters. Results During storage, PLTs stored in InterSol displayed significantly lower glucose concentration (P < 0.01), lower adenosine triphosphate levels (P < 0.01), a higher mean PLT volume (P < 0.01), a lower response to hypotonic shock response activity (P < 0.01) and a higher CD62P expression (P < 0.01) when compared with PLTs stored in plasma and PSM1-3 solutions. pH was maintained at > 6.8 (day 9) and swirling remained at the highest level (score = 2) for all units throughout storage. CONCLUSION: Our results suggest that PLTs stored in PAS with addition of magnesium, potassium and glucose (PSM2 and PSM3) and 20% plasma carry-over maintained metabolic and cellular characteristics, equivalent to PLTs stored in 100% plasma during 9 days of storage. Our results also suggest that presence of potassium in addition to magnesium or alternatively the concentration of phosphate as well as the supply of additional glucose to normal plasma levels improve in vitro data of PLTs stored in PAS.

Extended storage of whole blood before the preparation of blood components: in vitro effects on red blood cells in Erythro-Sol environment.

BACKGROUND AND OBJECTIVES: Routine procedures for extended storage of whole blood (WB) before the preparation of blood components are of interest primarily for logistical reasons. We stored red cell units in either Erythro-Sol 2 (E-Sol 2, test units, 150 ml added) or in saline-adenine-glucose-mannitol (SAG-M) (reference units, 100 ml added) that were prepared after storage of WB at room temperature for 8, 12, 16 or 19 h after blood collection. STUDY DESIGN AND METHODS: Red blood cells were stored for 42 days. We measured pH, glucose, lactate, haemolysis, red blood cell adenosine triphosphate and 2,3-diphosphoglycerate on days 1, 7, 14, 21, 28, 35 and 42. RESULTS: Haematocrits were significantly lower in E-Sol 2 than in SAG-M due to the higher volume of E-Sol 2 added compared to SAG-M. Significantly reduced levels were found in E-Sol 2 of extracellular pH (throughout storage after 8-h hold and initially after 12-, 16- or 19-h hold), of lactate (initially after 8-h hold and throughout storage after 12-, 16- or 19-h hold), and of haemolysis from day 35 in the 8-h and on day 42 in the 12-h hold group. Significantly increased levels of adenosine triphosphate were seen in E-Sol 2 after 8-h hold (from day 14) and after 12-h hold (at days 21, 35 and 42) compared to SAG-M. Significantly higher concentrations of 2,3-diphosphoglycerate were noticed primarily after 8-h hold of WB. CONCLUSION: The use of E-Sol 2 as a replacement for SAG-M does not significantly improve in vitro data after extended storage of WB at room temperature before preparation of blood components. However, after 8-h hold in vitro characteristics similar to or better than in fresh blood will be maintained for several weeks in E-Sol 2, a situation that makes E-Sol 2 superior to SAG-M when storage of WB is limited to 8 h. Some improvement was noted after 12-h hold as well.

In vitro and in vivo effects of potassium and magnesium on storage up to 7 days of apheresis platelet concentrates in platelet additive solution.

BACKGROUND AND OBJECTIVE: Prolonged storage of platelets up to 7 days provides improved availability, logistical management and decreased wastage. Beside methods of bacterial detection, addition of magnesium and potassium to the platelet storage solution (SSP+) may further improve the quality of platelets with extended storage. MATERIALS AND METHODS: Apheresis platelets from 10 donors were divided and stored in two different platelet additive solutions (PAS) (Intersol and SSP+) for a paired comparison. A variety of in vitro platelet function and metabolic assays were performed both on day 1 and after 7 days of storage. For in vivo study, platelets were labelled with either (111)Indium or (51)Chromium after 7 days of storage and were injected into the corresponding donor. Serial blood samples were drawn for recovery and survival measurements. RESULTS: In vitro parameters for SSP+ showed significantly reduced glycolysis (lower glucose consumption and decreased production of lactate), a higher hypotonic shock response (HSR) and the extent of shape change reactivity and a lower degree of platelet activation by means of RANTES (regulated on activation, normal, T cell-expressed, and secreted), CD62p and CD63 expression. Platelet recovery on day 7 was higher for Intersol as compared to SSP+, 65 +/- 11 vs. 53 +/- 13% (P = 0.023), and survival showed no difference 4.2 +/- 1.9 vs. 3.6 +/- 1.4 days. CONCLUSION: In vitro characteristics of platelets stored in PAS with addition of potassium and magnesium indicated higher quality, but this could not be verified by the in vivo parameters by means of recovery and survival.

Guidelines for the transfusion of red cells.

The following recommendations, which aim at standardising and rationalising clinical indications for the transfusion of red cells in Belgium, were drawn up by a working group of the Superior Health Council. To this end, the Superior Health Council organised an expert meeting devoted to "Guidelines for the transfusion of red cells" in collaboration with the Belgian Hematological Society. The experts discussed the indications for red cell transfusions, the ideal red cell concentrate, the practical issues of administering red cells, and red cell transfusions in patients in a critical condition. The recommendations formulated by the experts were validated by the working group with the purpose of harmonising red cell transfusion in Belgian hospitals.

Storage of buffy-coat-derived platelets in additive solutions at 4 degrees C and 22 degrees C: flow cytometry analysis of platelet glycoprotein expression.

BACKGROUND: The aim of our in vitro study is to compare the effects on platelet membrane glycoproteins that play an important role in the main functions of platelets, when platelets are stored for a period of 21 days at 4 degrees C or 22 degrees C. STUDY DESIGN AND METHODS: Platelet concentrates (PC) were prepared from pooled buffy-coats (BC) for paired studies (total eight pools from 80 BCs) by using the OrbiSac system. We divided each pool into two PCs and stored them at 4 degrees C or 22 degrees C. RESULTS: The activation marker CD62 remained almost unchanged during storage in all units. The expression of CD63 was higher in PCs stored at 22 degrees C than in those stored at 4 degrees C. No significant difference in CD41 expression was detected over time. The expression of CD42b declined during storage and even more in PCs stored at 4 degrees C until day 21 [day 14: mean flourscence intensity: 32.5 +/- 13.1 vs. 46.5 +/- 19.1], but the percentage of platelets expressing CD42b remained high in platelets stored at 4 degrees C, but gradually decreased at 22 degrees C (day 14: 95.0 +/- 1.5 vs. 59.0 +/- 9.9). Storage at 4 degrees C reduced the rate of glycolysis and maintained the pH better after day 10 than in PCs stored at 22 degrees C (day 14: 7.009 +/- 0.067 vs. 7.233 +/- 0.125). The concentration of regulated upon activation of normal T-cells expressed and secreted was higher in PCs stored at 22 degrees C than at 4 degrees C (day 7: 414.7 +/- 32.3 vs. 49.6 +/- 19.0). No response to extent of shape change and no swirling were detected at 4 degrees C. CONCLUSION: Platelets stored at 4 degrees C retain their in vitro characteristics better than those stored at 22 degrees C, except for parameters that reflect changes in shape. Storage at 4 degrees C is not associated with an increased expression of glycoprotein (GpIb, GpIIb/IIIa) and platelet activation markers (CD62p and CD63) as compared with storage at 22 degrees C.

Interruption of agitation of platelet concentrates: effects on in vitro parameters.

BACKGROUND AND OBJECTIVES: When platelet concentrates (PCs) are shipped from one centre to another, they may remain unagitated for a considerable period of time. It was therefore our aim to study the effects of interruption of agitation on the in vitro parameters of PCs stored in platelet additive solutions. MATERIALS AND METHODS: In this multicentre study, PCs were prepared either by apheresis or from pooled buffy coats, paired to minimize donor-dependent differences, and aliquoted into 3 units with a 'low concentration' (approximately 1 x 10(9) platelets/ml; groups A, B and C) and 3 units with a 'high concentration' (approximately 2 x 10(9) platelets/ml; groups D, E and F). The final composition of the storage medium was 30% plasma and 70% additive solution in all PCs. Either PASIIIM or Composol was used as the additive solution. Agitation was interrupted for 2 days (between days 3 and 5, groups A and D), or for 4 days (between days 1 and 5, groups B and E), and continuous agitation served as the reference (groups C and F). A number of in vitro parameters were used for testing on days 1, 5 and 7. RESULTS: On day 7, reference units C and F in PASIIIM had significantly higher pH values than the study units in PASIIIM, but all retained a pH of > 6.5 at 37 degrees C. Hypotonic shock response (HSR) results were significantly lower in the high concentration/4-day interruption group (E) than in the other groups. The low-concentration groups in PASIIIM, with agitation interrupted for either 2 days (group A) or 4 days (group B), did not have HSR values significantly different from the respective references. Study groups A, B, D and E in Composol, a solution lacking phosphate, had a pH of approximately 6.5 on day 7, which was significantly lower than that of the references and of the corresponding units in PASIIIM. The pH values were > 7.0 in reference groups C and F in Composol, not significantly different from those in PASIIIM. HSR values were also significantly lower in the Composol study groups. On the other hand, the reference Composol groups showed results similar to units in PASIIIM. CONCLUSIONS: PCs in PASIIIM additive solution with a platelet concentration of approximately 1 x 10(9)/ml can sustain 4 days without agitation. Phosphate may be of importance in maintaining good in vitro characteristics during interruption of agitation.

Automated preparation of platelet concentrates from pooled buffy coats: in vitro studies and experiences with the OrbiSac system.

BACKGROUND: The aim was to evaluate platelet concentrates (PCs) prepared by the automated OrbiSac system, from pooled buffy coats (BCs) stored in a platelet (PLT) additive solution. STUDY DESIGN AND METHODS: Experiment 1 was a paired in vitro study of PCs (from six BCs), prepared by automated and manual procedures. Experiments 2 and 3 evaluated PCs from OrbiSac (from six BCs); Experiment 3 included selection of BCs based on donor data. Experiment 4 was a paired in vitro study of PCs (from six BCs) with an integrated white blood cell (WBC) filter and two different storage containers. Experiment 5 evaluated PCs (from six BCs) from the OrbiSac with an integrated WBC filter. Experiment 6 was similar to Experiment 5 with computer-selected pools of 5 BCs. The in vitro studies evaluated the effects of 7-day storage of PLTs regarding PLT metabolism and disintegration. RESULTS: Experiments 1 and 4 had similar in vitro results. In Experiment 2, PLT content was 370 x 10(9) +/- 70 x 10(9) per PC and recovery from BCs was 76 +/- 6 percent. In Experiment 3, the PLT content was 380 x 10(9) +/- 50 x 10(9) per PC and variation was reduced compared with randomly pooled BCs. In Experiment 5, increased PLT content was found (420 x 10(9) +/- 70 x 10(9) per PC and recovery from BCs of 80 +/- 5%). In Experiment 6, five rather than six BCs gave 340 x 10(9) +/- 60 x 10(9) PLTs per PC and recovery was 79 +/- 5 percent. CONCLUSION: These in vitro studies suggest that the OrbiSac technique is equivalent to the standard manual method regarding the PLT in vitro characteristics during storage for 7 days. The results of standardizing the PLT count in PCs by selecting the BCs pools on the basis of the blood donor PLT concentration were encouraging.

Therapeutic efficacy of pooled buffy-coat platelet components prepared and stored with a platelet additive solution.

Despite the introduction of platelet additive solutions for the preparation of pooled platelet components, only a few studies of limited scope have evaluated the clinical efficacy of platelets stored in these solutions. The current report presents an analysis of data to evaluate the response to the transfusion of pooled buffy-coat components suspended in storage solution with reduced (35%) plasma content in comparison with 100% plasma products. During the euroSPRITE clinical trial of platelet components treated with a pathogen inactivation process, control treatment group platelet components were prepared in 100% allogeneic donor plasma (plasma control) or in platelet additive solution (T-Sol) mixed with plasma (T-Sol control). Control group thrombocytopenic patients received either plasma control or T-Sol control platelet components. One-hour and 24-h platelet count increments (CIs) and corrected count increments (CCIs) were analysed for these two types of preparation. In addition, haemostatic assessments were conducted for each transfusion. One-hour and 24-h mean platelet CIs and post-transfusion haemostatic scores were not significantly different for patients receiving platelet components suspended in 100% plasma and T-Sol plasma mixtures. Pooled buffy-coat platelet components prepared in reduced plasma content mixtures provided therapeutic platelet CIs with effective haemostasis.

Platelet storage solution affects on the accuracy of laboratory tests for platelet function: a multi-laboratory study.

BACKGROUND AND OBJECTIVES: Extent of shape change (ESC) and hypotonic shock response (HSR) have been widely used to characterize the in vitro function of platelets and have been shown to correlate with in vivo viability. These assays have been routinely performed using platelet-poor plasma (PPP) as the test sample diluent. Because of the increasing popularity of storing platelets in synthetic media, it is important to understand the effects of using these synthetic media as test diluents for ESC and HSR measurements. The objective of this study was to determine the effect of using platelet storage solutions vs. plasma for the in vitro testing of ESC and HSR. MATERIALS AND METHODS: Six laboratories participated in this study. Platelets were prepared by apheresis, the platelet-rich plasma (PRP) method, or derived from buffy-coats. Each platelet preparation was divided, half being stored in plasma and the other half in storage solution. ESC and HSR testing were performed in duplicate on days 1 and 5, using each of three diluents: autologous plasma; fresh-frozen plasma; or storage solution. RESULTS: For both ESC and HSR, dilutions made in each of the three diluents yielded significantly different results. Dilutions made in storage solutions were more than 30% lower for ESC and HSR than those made in autologous plasma (P < 0.0001). Dilutions made in thawed fresh-frozen plasma were more than 16% lower for ESC and HSR than those made in liquid autologous plasma (P < 0.0005). CONCLUSIONS: ESC and HSR test results are significantly affected by the test diluent. Platelets should be diluted in plasma (preferably autologous) for the in vitro testing of ESC and HSR, regardless of the media in which they are stored.

Storage of platelets in additive solutions: a multicentre study of the in vitro effects of potassium and magnesium.

BACKGROUND AND OBJECTIVES: In a preliminary study, the presence of potassium and magnesium in a modified synthetic medium (PAS-III) was found to have a significant influence on platelet metabolism (using apheresis-derived, as well as buffy-coat-derived platelets) when compared with standard PAS-III. The differences included reduced glycolysis, as evidenced by lower consumption of glucose and lower production of lactate, but also better preservation of pH and hypotonic shock response reactivity. The results suggested that storage in modified PAS-III containing 20% plasma was comparable to storage in standard PAS-III containing 30% plasma. To confirm the preliminary results and to evaluate the effects of different preparation protocols, an international multicentre study, which included 11 different sites, was conducted. MATERIALS AND METHODS: Platelets from 30 pools of approximately 20 buffy coat (BC) units each and 24 pooled apheresis platelet units were aliquoted for storage in plasma (reference) or synthetic medium using either a specific additive solution (PAS-III) containing 30% plasma or a modification of PAS-III containing 5.0 mm potassium and 1.5 mm magnesium (PAS-IIIM) and either 30% or 20% plasma. Units were stored at room temperature with agitation for 7 days during which in vitro testing was carried out for biochemical, haematological and functional parameters. RESULTS: Storage of platelets in PAS-IIIM resulted in a reduction in the rate of glycolysis and better retention of pH and hypotonic shock response reactivity. Storage in PAS-IIIM containing 20% plasma appeared to result in the retention of in vitro properties, similar to those observed during storage in standard PAS-III containing 30% plasma. CONCLUSIONS: The results of this study confirm the preliminary results. Similar results were seen with platelets prepared by BC and apheresis methods, despite differences in equipment, the preparation technique and in the final platelet contents achieved in the platelet units. Storage of platelets in PAS-IIIM should be considered to improve platelet function and allow plasma reduction to 20%.