Improved maintenance of 2,3 DPG and ATP in RBCs stored in a modified additive solution.

BACKGROUND: All currently used systems for the storage of RBCs result in loss of 2,3 DPG and an associated increase in affinity for oxygen. Previously, it was demonstrated that a hypotonic additive solution for RBC storage (Erythro-Sol) resulted in prolonged maintenance of 2,3 DPG when blood was collected in 0.5 CPD (half-strength CPD), but not when full-strength CPD was used. The present study aims at improving the quality of stored RBCs collected in ordinary CPD. STUDY DESIGN AND METHODS: A new formulation of Erythro-Sol (Erythro-Sol 2) (pH 8.8) in a larger volume (150 mL) was compared with Erythro-Sol (Erythro-Sol 1). In vitro measures during 49 days of storage in the two additives were compared using WBC-depleted RBCs after whole-blood collection in CPD and separation in an automated blood separation instrument (Optipress II, Baxter Healthcare). RESULTS: The maintenance of RBC ATP and 2,3 DPG was significantly better in Erythro-Sol 2 than in Erythro-Sol 1. The ATP concentration rose to approximately 30 percent above initial level in both systems; however, the maximum occurred on Day 21 in Erythro-Sol 2 as compared with Day 14 in Erythro-Sol 1. In RBCs stored in Erythro-Sol 2, the mean RBC 2,3 DPG concentration increased to 14 percent above initial level on Day 7, then decreased to the initial level on Day 14, whereas in Erythro-Sol 1, the 2,3 DPG had decreased to 85 and 50 percent on Days 7 and 14, respectively. Both intracellular pH and extracellular pH were slightly higher in Erythro-Sol 2 than in Erythro-Sol 1 units but decreased rapidly during the first storage week, which seems to have been the major reason for the limitation in the time of maintenance of 2,3 DPG. Hemolysis was very low in both systems, 0.14 to 0.17 percent on Day 49. The additional amount of inorganic phosphate submitted with Erythro-Sol 2 did not raise concern because the phosphate content in the storage medium, being 1.3 +/- 0.2 mmoL on Day 0, decreased to values below 1 mmoL during most of subsequent storage. CONCLUSION: Erythro-Sol 2 is an improved additive solution for the storage of RBCs.

Photochemical inactivation of bacteria and HIV in buffy-coat-derived platelet concentrates under conditions that preserve in vitro platelet function.

BACKGROUND AND OBJECTIVES: A photochemical process has been tested for the inactivation of viruses and bacteria in buffy-coat derived platelet concentrates (BC PCs). MATERIALS AND METHODS: BC PCs in 35% CPD plasma and 65% platelet-additive solution (PAS III) were exposed to photochemical treatment (PCT) with 150 microM of the psoralen S-59 and a 3 J/cm(2) treatment with long-wavelength ultraviolet light (UVA, 320-400 nm). Platelet function was evaluated following PCT using a panel of in vitro assays. RESULTS: This PCT process was highly effective at inactivating gram-positive bacteria (Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis) and gram-negative bacteria (Enterobacter aerogenes, Pseudomonas aeruginosa, Serratia marcescens). No viable bacteria were detected following PCT and 7 days of platelet storage while bacterial growth was detected in paired untreated control BC PCs. Complete inactivation of the gram-positive Bacillus cereus was achieved only in one of two replicate experiments with BC PCs. PCT was also highly effective for inactivation of human immunodeficiency virus HIV-1 in BC PCs inoculated with approximately 10(6) tissue culture infectious doses per milliliter (TCID(50)/ml) of cell-associated HIV-1. Rapid inactivation was observed with increasing UVA doses: with 150 microM S-59 and a 1 J/cm(2) treatment of UVA, a reduction of 5.6+/-0.5 log TCID(50)/ml was achieved, and a reduction of >6.4 log TCID(50)/ml was achieved with 150 microM S-59 and a 3 J/cm(2) treatment of UVA. No physiologically relevant differences in platelet functions were found between the test and the control BC PCs during 7 days of storage. CONCLUSION: PCT with 150 microM S-59 and a 3 J/cm(2) UVA treatment does not adversely affect in vitro properties of BC PCs stored at 22 degrees C for 7 days. The PCT process inactivated bacteria and HIV-1 inoculated into the BC PCs. These results extend the earlier reported efficacy of PCT apheresis PCs to BC PCs.

Standardized units of RBCs: is it time for implementation?

BACKGROUND: Current practice for the preparation of RBCs from whole blood for transfusion results in poorly standardized contents of RBC Hb. The principle of apheresis, metering the anticoagulant into the collected blood, which is pumped into an empty container, allows variation in the collected volume according to properties of the donor. STUDY DESIGN AND METHODS: The total Hb mass of each person in a representative group of Swedish blood donors was evaluated by using Hb concentration and blood volume (BV), with the latter calculated from each donor's weight and height. The number of blood units that could be collected without exceeding 13 percent of the BV was estimated at a standardized content of RBC Hb set at 40, 45, and 50 g. RESULTS: With Hb standards of 45 and 50 g per unit of RBCs, it would be possible to collect 1 unit, but not more, from 93 female donors in the study; with 40 g of Hb as the standard, 2 units could be collected from 6 percent of the donors. Using a standard of 40 g of Hb, it would be possible to collect 2 units or more from 95 percent of 121 male donors. The corresponding figures at Hb standards of 45 and 50 g were 81 and 50 percent, respectively, of the male donors. The largest number of units that could be collected would thus be obtained at a 40-g Hb standard. However, the greatest total mass of RBC Hb would have been obtained at 45 g. Even the yield of plasma would reach a maximum at this RBC Hb standard. CONCLUSION: Depending on the donor's Hb and BV, it is possible to collect either 1 or 2 units of RBCs without exceeding 13 percent of any donor's BV, provided the collected volume of blood in each unit is less than the current standard. Such practice would allow better use of the donor population. Two-unit blood collections may reduce donor exposure in transfusions. Applying a standard at 45 g of RBC Hb per unit was found to permit the collection of maximum RBC Hb and plasma in the evaluated population of Scandinavian donors. Perhaps it is time to discuss a change in current rules for the preparation of RBCs for transfusion.

Storage of blood components.

Recent studies have shown that a restrictive transfusion policy results in lower mortality in patients undergoing surgery. The negative effects of red cell transfusion are associated with the presence of contaminating leukocytes, leukocyte products, and probably also with effects of nonviable and poorly functioning red cells. By relatively simple means it is possible to improve the quality of red cells in these respects. The removal of leukocytes from platelet concentrates (PCs) is even more important because of high immunogenicity and capacity to produce cytokines under the storage conditions applied. Prestorage leukocyte removal has clear advantages. Bacterial contamination of PCs is common, but fatal bacterial complications are rare because most contaminating microorganisms grow slowly and do not produce toxins, which are frequent causes of death. Suitable methods for routine bacterial culture of PCs are available and used in some countries.

A new apheresis procedure for the preparation of high-quality red cells and plasma.

BACKGROUND: Multicomponent apheresis is an alternative way of preparing blood components that avoids the delay between collection and separation seen with standard whole-blood techniques. STUDY DESIGN AND METHODS: An apheresis device has been modified to facilitate the combined collection of a unit (250 mL) of red cells (RBCs) and a high-volume unit (475 mL) of plasma. The procedure, using 8-percent ACD-A, has been tested in two European blood centers. Each center performed 20 procedures for in vitro evaluation of collected RBCs and plasma and 10 procedures for evaluation of in vivo RBC recovery. All RBCs were white cell reduced by filtration. One-half of the RBC units were stored in the additive solution Adsol and one-half in another such solution (Erythro-Sol). RESULTS: The target volumes of RBCs and plasma were obtained in 27 minutes (range, 20-44 min) by using three to six cycles in a single-needle procedure. Saline (275 mL) was used to replace fluid volume withdrawn in excess of standard whole-blood donation. No side effects occurred, with the exception of minor signs of hypocalcemia. RBC ATP was well maintained (>65% at Day 42) during storage; 2,3-DPG was less well maintained, with virtually none remaining at Day 21 in either Adsol or Erythro-Sol. The RBC in vivo recoveries, after 42 days of storage at 4+/-2 degrees C determined by the single-label method, were 86.7+/-7.2 percent (Erythro-Sol) and 84.4+/-8.1 percent (Adsol). Mean plasma factor VIII levels were >100 percent in all test groups. CONCLUSION: A novel automated technique for the simultaneous collection and preparation of RBCs and plasma has been evaluated. The apheresis procedure was acceptable and well tolerated by donors, and it resulted in high-quality blood components. Further optimization of the system should yield a practicable component suitable for routine use in blood banks.

Storage of whole blood before separation: the effect of temperature on red cell 2,3 DPG and the accumulation of lactate.

BACKGROUND: Although whole blood intended for component preparation is commonly left to cool at ambient temperature, knowledge is insufficient as to the effects this may have on red cell quality, in particular after a prolonged hold. STUDY DESIGN AND METHODS: Whole blood collected in ACD-A (7% wt/wt) and CPD (12% wt/wt) was incubated at 4, 10, 15, 20, 25, and 30 degrees C for 24 hours. Blood gases, pH, bicarbonate, glucose, lactate, and red cell 2,3 DPG were investigated. RESULTS: When the blood was stored at 30 degrees C, the 2,3 DPG concentration decreased within 4 hours from 858 +/- 106 to 316 +/- 172 mmol per mol of hemoglobin (a 63% decrease); 99 percent was lost within 18 hours. At 25 degrees C, 46 percent was lost within 4 hours and 94 percent within 18 hours; at 20 degrees C, the decrease at 18 hours was 62 percent and that at 15 degrees C was 24 percent. No loss of 2,3 DPG was observed at 4 degrees C and 10 degrees C storage. No difference was attributable to the anticoagulant used. After 24 hours, the lactate concentration at 15 degrees C was 2.9 times the original, that at 20 degrees C was 3.8 times the original, that at 25 degrees C was 7.0 times, and that at 30 degrees C was 9.2 times. CONCLUSIONS: With current anticoagulants, storage of whole blood at temperatures of 25 to 30 degrees C before separation causes a great and rapid loss of 2,3 DPG and an accumulation of acid metabolites. In a hold of blood for >4 hours, rapid cooling is desirable to avoid initial loss of 2,3 DPG.

Liquid-stored red blood cells for transfusion. A status report.

Blood transfusion in a modern sense means the transfusion of red cells, when necessary supplemented by other components. The demand for plasma and plasma fractions and for platelets for therapeutic use has had an influence on the technique for preparing red cells. Automated devices have made it possible to perform collection as well as separation under more standardized conditions. Improved techniques for storage of red cells have prolonged the shelf life somewhat but most of the available methods disregard the rapid loss of 2,3-diphosphoglycerate and the accompanying increase in oxygen affinity. Methods are available which reduce the number of contaminating leukocytes to low levels, but information is still incomplete as to the degree of depletion actually needed.

Increased anticoagulant osmolality improves separation of leukocytes from red blood cells (RBC).

BACKGROUND: The bottom-and-top (BAT) procedure separates the buffy coat (BC) from plasma and red blood cells (RBC). The contents of mononuclear cells (MNC) remaining in the RBC are about 1 x 10(6) cells/unit, whereas the granulocytes are removed less effectively, 500-800 x 10(6) or more remaining in the RBC unit. The aim was to improve the separation efficacy by collecting the blood in an hyperosmolar anticoagulant, followed by BAT separation. It was expected that the red cells would shrink, thereby increasing their density, while the granulocytes would not change volume and density. STUDY DESIGN AND METHODS: 18 donors were included in the study, 12 in the test group and 6 in the control group. CPD-SAGM bags were used, with a modification of the anticoagulant by removal of 20-ml CPD from all units and addition of 20-ml mannitol (test group) or 20 ml of isotonic saline (control group). The collected blood units were cooled on butanediol plates for 2-4 h, then centrifuged and separated into components. The levels of leukocytes in the whole blood, the BC and the RBC were determined by flow cytometry gated for intact CD45+ cells. A number of other tests were performed during 42-day storage. RESULTS: The plasma yield was slightly higher in the test group than in the control group (ns). The contents of leukocytes (CD 45+ intact cells) in the RBC units were 32 +/- 20 x 10(6) in the test group and 573 +/- 241 x 10(6) in the control group. The numbers of MNC were 1.2 +/- 0.6 x 10(6) and 2.6 +/- 1.8 x 10(6), respectively. The RBC 2,3-DPG concentration was slightly better maintained in the test group at day 7 of refrigerated storage (p = 0.0027), but most other tested parameters showed no difference during 42-day storage. It was possible to prepare platelet concentrates with good yield using the pooled-BC method. CONCLUSION: This study indicates that considerable improvement in the BAT procedure can be obtained if the anticoagulant is made hypertonic by the addition of mannitol. This is achieved without altering the already low levels of MNC and keeping the same quality.

Pre-separation storage of whole blood: the effect of temperature on red cell 2,3-diphosphoglycerate and myeloperoxidase in plasma.

BACKGROUND: Although whole blood intended for component preparation is commonly left to cool at ambient temperature, knowledge is insufficient concerning what effects this may have on red blood cell (RBC) quality, in particular after a prolonged hold. STUDY DESIGN AND METHODS: Whole blood collected in CPD was incubated at 20 degrees C and 28 degrees C for 6 h designed as a paired study. Blood components were prepared and the red blood cell concentrates (RBCs) were stored for 28 days at 4 degrees C +/- 2 degrees C. Blood gases, pH, glucose, lactate, adenosine triphosphate (ATP), 2,3-diphosphoglycerate (2,3-DPG) and plasma myeloperoxidase (MPO) were investigated. RESULTS: After 6 h the 2,3-DPG concentrations had lowered to 88% (20 degrees C) and 54% (28 degrees C) of initial levels, respectively. The difference was significant and was maintained for 28 days, although, at low levels from day 7 (28 degrees C) and day 14 (20 degrees C) of storage. ATP was maintained at the initial level in both groups during the first 6 h of storage but after component separation the levels were significantly higher in the 28 degrees C group during the first 5 days. The release of myeloperoxidase (MPO) was significantly higher in the non-cooled group than in the cooled group. CONCLUSIONS: Pre-separation holding for 6 h of whole blood at temperatures of 28 degrees C causes a great and rapid loss of 2,3-DPG and considerable formation of acid metabolites resulting in clearly subnormal 2,3-DPG levels even on day 1. Active pre-separation cooling to 20 degrees C is to be recommended.

Preparation and preservation of red cells.

BACKGROUND: The production of blood components has undergone several changes during the last decades. METHODS: Red blood cells will have slightly different properties depending on the way of preparation: whether a hard or soft spin has been used, whether platelets and/or leukocytes have been removed or not, and whether the red cells have been suspended in part of the original plasma or in an additive solution. Automated techniques are now often used for the separation of buffy coats, red cells and plasma. Recently, apheresis techniques have been applied for the preparation of red cells, mostly in combination with plasma or platelets. Continuous addition of the anticoagulant during collection reduces the delay between collection and separation, but the cost is higher and donor time longer. RESULTS: Most of the methods for the preparation and storage of red cells allow 35-42 days of storage with a mean in vivo recovery of > 75%. However, the content of erythrocyte 2,3-DPG is commonly lost within 1-2 weeks, caused by the accumulation of acid metabolites, but can be maintained longer with new systems of storage. Leukodepletion of red cells by filtration is used increasingly, but its importance in the majority of transfusions is still unclear. CONCLUSION: New options for the preparation and storage of red blood cells are available and undergo continuous evaluation.

Improved blood preservation with 0.5CPD erythro-sol. Coagulation factor VIII activity and erythrocyte quality after delayed separation of blood.

BACKGROUND AND OBJECTIVES: Delay between blood collection and the separation of its components may result in lowered yield of factor VIII (FVIII) and loss of 2,3-biphosphoglycerate (2,3-BPG). This study was to see whether the use of 0.5 CPD resulted in better preservation of FVIII and maintenance of 2,3-BPG. MATERIALS AND METHODS: 55 units of blood were collected in 0.5CPD and 48 in CPD SAG-M. Ten of the collections were paired, so that the same donors were bled in a single session partly in an 0.5CPD system and partly in CPD SAG-M. After collection, the blood was promptly cooled to 20 degrees C and stored at that temperature for up to 24 h. RESULTS: Preservation of FVIII activity was significantly better in 0.5CPD compared with CPD. The content of von Willebrand factor was stable in the anticoagulant solutions for 24 h at that temperature. Plasma separated from both media had how levels of prothrombin fragment 1 + 2 and complement activation. Paired collections substantiated previous reports that red cell storage is significantly improved in 0.5CPD compared with CPD SAG-M with respect to 2,3-BPG and haemolysis. CONCLUSIONS: Red cell metabolism and oxygen-releasing capacity are kept at acceptable levels in 0.5CPD blood for 24 h at 20 degrees C before component separation. The concentration of red cell 2,3-BPG remained at normal or slightly subnormal levels during further storage in 0.5CPD at 4 degrees C for 2-4 weeks before gradual decay to an average of 39% at 48 days.

International forum: Europe. Buffy-coat-derived platelet concentrates: Swedish experience.

The need for source material for plasma products such as factor VIII preparations and improving the quality of red cells for transfusion became determining factors in the choice of methods for blood components in the 1970s and 1980s in Sweden. The possibility to make platelet concentrates (PC) from buffy coats (BC-PC) instead of from platelet-rich plasma (PRP-PC), as first described in England and The Netherlands, using an additive solution as the major component of the platelet storage medium, as first described by Rock et al., has been shown to influence favourably the national supply of blood components and has become accepted as the normal standard procedure in the first half of the 1990s. Leucocyte-depleted PCs, produced from pools of 4-6 BCs, used in all multiple platelet transfusions to thrombocytopenic patients, have strongly reduced the demand for HLA compatible PCs. Nationwide, 79% of the demand of PCs is supplied as BC-PCs, mostly leuco-depleted which, so far, have compared favourably with apheresis-PCs for cost-effectiveness.

Storage of buffy coat preparations at 22 degrees C in plastic containers with different gas permeability.

BACKGROUND: Buffy coats (BCs) are used as an alternative to platelet-rich plasma in the preparation of platelet concentrates (PCs). For this purpose the BCs have to be stored for same time at 20-24 degrees C which implies cellular metabolic activity. However, little information is available concerning the effects of a number of factors which may influence the suitability of the preparation as the source of PC. STUDY DESIGN AND METHODS: We studied the effects on BCs of a high and low gas permeability of the wall of the plastic containers, PL2209 and PL146, respectively, mixing versus non-mixing during storage for 48 h at 22 degrees C, and two types of anticoagulant solutions, CPD and half strength citrate CPD (0.5CPD). The buffy coats were prepared by the bottom and top technique. The median values of volume and haematrocrit were 58-64 ml and 39-45%, respectively. A total of 48 BCs were tested. Blood gases, pH, bicarbonate concentration and haemolysis were determined in the blood mixtures and beta-thromboglobulin (beta-TG), lactate dehydrogenase (LDH), complement factor 3a, and elastase in the extracellular fluid. RESULTS: The pH decreased in all units but to a lesser extent in PL2209 containers than in PL146 units. In the former the pCO2 decreased slowly in contrast to the latter where it increased by about 50%. Mixing during storage increased the pH and decreased the pCO2 in 0.5CPD-PL146 and CPD-PL2209 units, as compared to resting, while no effects of mixing were observed in the other groups. The pO2 decreased to low levels in PL146 units. The haemolysis and LDH release were higher in mixed than in unmixed units. The initial beta-TG levels were lowest in 0.5CPD-PL146 units which also had the lowest 24-hour levels. The release of beta-TG during storage was smallest in CPD resting units. The elastase release was significantly higher in 0.5CPD than in CPD units already from the beginning of storage and increased during storage at about the same rate irrespective of mixing. The C3a levels were higher in 0.5CPD-PL2209 units than in the other units at 2 h. Storage for 24 h caused an increase by 2-3 times of the original level without any clear relation to storage conditions. CONCLUSIONS: In BC units accumulation of CO2 occurs in containers with low gas permeability. These also show the most rapid pH decrease during storage. Prolonged holding of BCs puts extra emphasis on the need of satisfactory gas permeability of the container for platelet storage in BC-derived PCs. Continuous mixing causes red cell damage and does not seem to have any clear benefit. The release of granulocyte elastase was higher in 0.5CPD than in CPD units but there was no indication of an associated increase in platelet activation. SUMMARY: Study of buffy coats stored in various media and containers at 22 degrees C suggests that it is better to restrict storage to 24 h or less to avoid activation or other deleterious effects on the platelets.

Computerized delivery control--a useful and safe complement to the type and screen compatibility testing.

OBJECTIVES: Faster and less labor-intensive crossmatching procedures are needed, but they must be as safe as the traditional antiglobulin method. We present twelve years' experience with a procedure involving antibody screening, blood group checks, and computerized delivery control (ABCD test). METHODS: We use a computer for validation and printing documents and declaring compatibility between patient and blood component, based on screening results and earlier-recorded data about the patient. RESULTS: Of 257,400 units transfused during the period, 90% were declared compatible through the ABCD procedure, and 10% had to be crossmatched. We observed no hemolytic transfusion complications due to a failure of the procedure to detect red cell alloantibodies. Labor in the testing laboratory was reduced by 65% compared to a previous crossmatching period. Fewer blood units were returned unused. CONCLUSION: The procedure using a computerized system as a guard against human mistakes has been found to be safe and reliable and is now widely used in Sweden.

Clinical and laboratory experience with erythrocyte and platelet preparations from a 0.5CPD Erythro-Sol opti system.

BACKGROUND: Red blood cells stored as concentrates or suspensions in additive solutions change rapidly their oxygen affinity mainly due to the loss of 2,3-diphosphoglycerate (2,3-DPG). When collected in CPD with half of the normal concentration of citrate and citric acid (0.5CPD) and stored in a new additive solution (Erythro-Sol), 2,3-DPG is better maintained. No studies of the oxygen affinity of red cells stored under these conditions have been published. In Erythro-Sol, red cells have a satisfactory in vivo recovery for 49 days but the conditions after 28 days, within which time most red cell units are transfused, have not been investigated. Of importance is also to be able to make platelet concentrates (PCs) from 0.5CPD blood. Little data are available concerning the clinical usefulness of platelets prepared from 0.5CPD buffy coats (BCs). METHODS: Blood was collected in 0.5CPD, held at 20 degrees C for 3-4 h, then separated with the bottom-and-top technique into red cells, plasma and BC. In a storage experiment with 6 U the 2,3-DPG and P50 values were determined weekly and a number of in vitro parameters were tested on day 28. In 6 donors the in vivo recovery and survival of red cells were determined using a single-chromium technique. Transfusions of 212 0.5CPD-Erythro-Sol red cell units were given to hematological patients under supervision. PCs derived from pools of 0.5CPD BCs suspended in PAS2 (T-Sol) were transfused to 20 thrombocytopenic patients and compared with CPD-BC-PCs suspended in PASI. Corrected count increments (CCI) were determined. RESULTS: The erythrocyte 2,3-DPG and P50 values were normal or slightly subnormal initially but increased to supernormal levels during the 1 week, and remained at these levels for a further 1-3 weeks; the 2,3-DPG was two thirds of normal after 28 days, the P50 was 3.72 +/- 0.28 kPa after 14 days and 2.84 +/- 0.41 after 28 days (mean +/- SD). The P50 values corresponded closely (r2 = 0.903) to 2,3-DPG. The in vivo recovery of 4-week-stored red cells was 89.6 +/- 5.5% and the T50 was 32.2 +/- 2.0 days. No adverse effects were observed in the transfusions. The CCI values did not differ between test and control groups; in both, 3- to 5-day-stored PCs gave lower CCI than fresh (0-2 days) PCs. Patients with acute myeloid leukemia AML (n = 11) had significantly lower CCI values than patients with myelodysplastic syndrome, myeloma and lymphoma (n = 9; CCI 1 h: p = 0.001; CCI 24 h: p = 0.006). CONCLUSIONS: Red cells stored in Erythro-Sol sustain a normal or slightly lowered oxygen affinity for 2-4 weeks, their viability is excellent, and they are well tolerated in clinical transfusions. Platelets prepared from 0.5CPD-BCs cause CCI, of the same magnitude as CPD-BCs.

How can we improve platelet preparation and storage?

The use of platelet additive solutions to replace the major part of plasma as storage medium can improve storage through supply of fuel in platelet metabolism. It is important to avoid platelet activation, e.g. through optimal anticoagulation and gentle procedures at preparation. Leucodepletion of platelet concentrates (PCs) reduces HLA immunization and therapeutic refractoriness. Leucofiltration has become common to obtain leucocyte-depleted PCs, but frequently results in considerable platelet loss. Attempts at improvements must be validated, e.g. by testing post-transfusion increments and function in vivo. The in vitro bleeding-time test seems to be a valuable tool for the latter purpose. Bacterial contamination of PCs occur more commonly than so far believed, however, severe clinical complications seem to be relatively rare. Newly available methods for bacterial culture are sufficiently rapid and sensitive to be useful in PC testing. Bacterial decontamination, e.g. using psoralen-UVA, may be a future possibility for obtaining safer PCs.