Routine use of a rapid test to detect bacteria at the time of issue for nonleukoreduced,whole blood–derived platelets

BACKGROUND: The Pan Genera detection (PGD) test is used to screen platelet (PLT) products for bacterial contamination. We report the experience of using the PGD test on whole blood–derived PLTs (WBPs) at two large centralized transfusion services (CTS). STUDY DESIGN AND METHODS: Records of PGD test results were retrospectively reviewed. The PGD test was performed on individual WBP units or pools of WBPs ranging in size from 2 to 6 units at the time of issue. Bacterial culture was performed on PLT products with positive PGD tests, and at one CTS, the available cocomponents. RESULTS: A total of 70,561 WBP pools were screened with the PGD test. There were seven true‐positive PGD tests and 242 false‐positive tests (positive predictive value of PGD test, 2.81%). The overall contamination rate was 99 per 10⁶ WBP pools (1:10,080; 95% confidence interval [CI], 40‐204), and the false‐positive rate was 3430 per 10⁶ WBP pools (1:292; 95% CI, 3011‐3890). All seven bacterial isolates were Gram positive. The median age of the individual WBP units in the seven contaminated pools was 5 days (range, 3‐5 days) compared to 4 days (range, 1‐5 days) in the false‐positive pools (p = 0.0012). The same bacteria isolated from a positive PLT pool also grew in one red blood cell cocomponent. CONCLUSION: After testing more than 70,000 WBP pools at two large CTSs, the rate of contaminated WBP pools detected by the PGD test was 99 per 10⁶ pools (1:10,080).     

Bacterial screening of outdated buffy coat platelet pools using a culture system and a rapid immunoassay

BACKGROUND: Canadian Blood Services performs bacterial screening of buffy coat platelet pools (BCPs) using aerobic BacT/ALERT cultures. This study aimed to determine the rate of detection failures during initial platelet (PLT) screening and evaluate the introduction of anaerobic cultures and immunoassay testing to assess the safety of extending PLT storage beyond 5 days. STUDY DESIGN AND METHODS: Outdated (7‐ to 10‐day‐old) BCPs that tested negative during initial screening were assayed with BacT/ALERT and the Verax PLT Pan Genera detection (PGD) test, an immunoassay that detects Gram‐positive (GP) and Gram‐negative (GN) bacteria. BacT/ALERT aerobic and anaerobic culture bottles were inoculated with 8 to 10 mL of BCP and incubated for up to 6 days. The PGD test was performed following manufacturer's instructions. Positive results were confirmed using the BacT/ALERT and PGD tests, blood agar culture, and Gram staining. Invalid PGD results were investigated. RESULTS: A total of 4002 BCPs were tested with one (0.025%) true positive (Staphylococcus epidermidis) found by both the BacT/ALERT and the PGD assays. Fifty‐four (1.35%) false‐positive BacT/ALERT cultures were obtained mainly due to instrument errors involving anaerobic cultures. Eleven (0.27%) false‐positive PGD tests were observed in the GP window of the strip. Forty‐nine (1.2%) invalid PGD results were obtained mostly before implementation of a humidity chamber. CONCLUSION: Testing of outdated BCPs suggests that introducing anaerobic cultures would result in significant PLT wastage due to a high rate of false positives. Contaminated BCPs still escape detection during initial testing; therefore, extension of PLT storage may be possible if repeat screening is performed before transfusion.     

Evaluation of the automated collection and extended storage of apheresis platelets in additive solution

BACKGROUND: Collecting apheresis platelets (PLTs) into additive solution has many potential benefits. The new Trima software (Version 6.0, CaridianBCT) allows automated addition of PLT additive solution (PAS) after collection, compared to Trima Version 5.1, which only collects PLTs into plasma. The aim of this study was to compare PLT quality during extended storage, after collection with the different Trima systems. STUDY DESIGN AND METHODS: Apheresis PLTs were collected using both Trima Accel apheresis systems. The test PLT units (n = 12) were collected using the new Trima Version 6.0 into PLT AS (PAS‐IIIM), while the control units (n = 8) were collected into autologous plasma using Trima Version 5.1. All units were stored for 9 days, and in vitro cell quality variables were evaluated during this time. RESULTS: PLTs collected in PAS‐IIIM maintained a stable pH between 7.2 and 7.4, whereas plasma‐stored apheresis units exhibited significantly increased acidity during storage, due to lactate accumulation and bicarbonate exhaustion. Plasma‐stored PLTs also demonstrated a more rapid consumption of glucose. However, there was little difference in PLT activation or cytokine secretion between PAS‐IIIM and control PLTs. CONCLUSION: These data indicate that apheresis PLT concentrates collected in PAS‐IIIM, using Trima Version 6.0 software, maintained acceptable PLT metabolic and cellular characteristics until Day 9 of storage.     

In vitro and in vivo evaluation of apheresis platelets stored for 5 days in 65% platelet additive solution/35% plasma

BACKGROUND: In the United States, apheresis platelets (PLTs) are suspended in autologous plasma. PLT additive solutions, long used in Europe, decrease recipient allergic reactions and may reduce the risk of transfusion‐related acute lung injury. We evaluated Amicus‐collected PLTs stored in platelet additive solution (PAS) III (InterSol) for 5 days. STUDY DESIGN AND METHODS: In Study 1, 71 subjects donated two products on a single day—one each stored in 100% plasma or 65% PAS III/35% plasma. Products underwent standard in vitro testing on Days 1 and 5. In Study 2, 43 additional subjects provided Amicus products stored for 5 days in 65% PAS III/35% plasma for in vivo radiolabeled recovery and survival determinations. The effect of approximately 2500 cGy Day 1 gamma irradiation was evaluated in a subset of products. RESULTS: PAS III PLTs (n = 70) had a median Day 5 pH_22°C of 7.2 (lower 95%, 95% tolerance limit, 6.9). Mean Day 5 recovery and survival of radiolabeled PAS III PLTs (n = 33) were, respectively, 80.5 and 72.1%, of fresh autologous PLTs. With 95% confidence, these values were at least 66% of fresh PLT recovery and 58% of survival. All in vitro variables remained within ranges seen in licensed products for irradiated and nonirradiated PAS III PLTs. CONCLUSION: Leukoreduced Amicus PLTs stored in 65% PAS III/35% plasma in PL‐2410 containers maintained pH ≥ 6.9 throughout 5 days' storage. Radiolabeled PLT recovery and survival values met US Food and Drug Administration statistical criteria. Gamma‐irradiated PAS III PLTs demonstrated no significant adverse effects due to irradiation in in vitro testing.     

Use of hemovigilance data to evaluate the effectiveness of diversion and bacterial detection

BACKGROUND: Several preventive measures, including diversion of the first aliquot of blood and culturing of platelet (PLT) components, have been implemented to decrease the risk of transfusion‐transmitted bacterial infections (TTBIs). We evaluated the effectiveness of these measures in Québec using hemovigilance data from January 2000 to December 2008. STUDY DESIGN AND METHODS: Adverse transfusion reactions were reported to the Québec Ministry of Health by transfusion safety officers. Initial aliquot diversion, already in place for apheresis PLTs, was added to all whole blood collections in early 2003. Bacterial detection was implemented in March 2003 for apheresis PLTs and February 2005 for whole blood–derived PLTs (WBDPs). RESULTS: The incidence of probable and definite TTBIs associated with WBDPs decreased from 1 in 2655 to 1 in 27,737 five‐unit pools (p = 0.004) after implementation of diversion. There were no reports of TTBIs with WBDPs after culture was added to diversion, further reducing the risk to 1 in 58,123 five‐unit pools (p < 0.001). There was only one TTBI associated with apheresis PLTs during the 9‐year period, which occurred after implementation of both diversion and culture. CONCLUSION: Hemovigilance data demonstrated a highly significant decrease in TTBIs associated with WBDPs, mainly attributed to the implementation of diversion. However, diversion and culture do not totally abolish the risk of TTBIs.     

Bacterial contamination in platelets: incremental improvements drive down but do not eliminate risk

BACKGROUND: Bacterial contamination of platelet components (PCs) remains an important cause of transfusion‐associated infectious risk. In 2004, Canadian Blood Services (CBS) implemented bacterial testing of PCs using the BacT/ALERT 3D system (bioMérieux). This system has been validated and implemented and continuous monitoring of culture rates allows gathering of data regarding true and false positives as well as false negatives. STUDY DESIGN AND METHODS: National data gathered between March 2004 and October 2010 from 12 CBS sites were analyzed to compare bacterial contamination rates across three platelet (PLT) preparation methods: apheresis, buffy coat, and PLT‐rich plasma. Data were compared before and after implementation of protocol changes that may affect bacterial detection or contamination rates. RESULTS: Initial positive rates among the three production methods were significantly different, with apheresis PCs being the highest. The rates of confirmed positives among production methods did not differ significantly (p = 0.668). Increasing sample testing volumes from 4 to 6 mL to 8 to 10 mL significantly increased the rate of initial positives, while confirmed positives increased from 0.64 to 1.63 per 10,000, approaching significance (p = 0.055). Changing the skin disinfection method from a two‐step to a one‐step protocol did not significantly alter the rate of confirmed positives. During the period of data analysis, eight false‐negative cases were reported, with five implicated in adverse transfusion reactions. CONCLUSION: Bacterial testing of PCs and implementation of improved protocols are incrementally effective in reducing the risk of transfusion of bacterially contaminated PLT concentrates; however, the continued occurrence of false‐negative results means the risk has not been eliminated.     

Recovery, survival, and function of transfused platelets and detection of platelet engraftment after allogeneic stem cell transplantation

BACKGROUND: Recovery and survival of transfused platelets (PLTs) are usually assessed by radioisotope labeling methods for evaluation of transfusion efficacy and new progress in the processing of PLT concentrates. Alternative, nonradioactive methods are warranted. STUDY DESIGN AND METHODS: A multicolor flow cytometry method was developed for simultaneous studies of recovery, survival, and function of transfused PLTs. Eight consecutive patients undergoing allogeneic stem cell transplantation (TX) were transfused with apheresis PLTs of nonself human leukocyte antigen (HLA) Class I types, and HLA Class I discrepancy between donor and recipient was used to identify transfused PLTs. Hematologic status and HLA Class I surface expression were analyzed immediately before transfusion, 1 and 6 hours after transfusion, and daily during the subsequent week. PLT activation was assessed by surface expression of CD63, CD62P, or CD42a, before and after stimulation with thrombin receptor agonist peptide. RESULTS: PLT recovery was 43, 41, and 31% for fresh (5‐72 hr old) and 30, 27, and 17% for stored (73‐148 hr old) PLTs, after 1, 6, and 15 to 28 hours, respectively. Survival of fresh versus stored PLTs were 160 and 105 hours, respectively. Spontaneous PLT activation and residual activation potential were almost equal for fresh and stored PLTs. PLT engraftment was detected between Day 7 and Day 9, which was significantly earlier than first sign of neutrophil engraftment (Days 11‐19; p = 0.01). CONCLUSION: Flow cytometry is an attractive alternative to radiolabeling of PLTs for simultaneous studies of survival, recovery, and function of transfused PLTs and early detection of PLT engraftment after allogeneic stem cell TX.     

Storing apheresis platelets without agitation with simulated shipping conditions during two separate periods: immediately after collection and subsequently between Day 2 and Day 3

BACKGROUND: Apheresis platelet (PLT) units are not routinely agitated during transit. Our study compared the in vitro properties of apheresis PLT units that were stored with continuous agitation (CA) and without continuous agitation (WCA) during two separate periods, immediately after collection and between Day 2 and Day 3 of storage. STUDY DESIGN AND METHODS: Two identical apheresis PLTs units were prepared from collections with Amicus (n = 11, Fenwal, Inc.) and Trima (n = 10, CaridianBCT) cell separators. One apheresis PLT unit was continuously agitated, starting routinely within 30 minutes of collection, and an identical apheresis PLT unit was held without agitation initially for 7 to 8 hours and subsequently for 24 hours between Day 2 and Day 3 of storage. The apheresis PLT units were maintained WCA at 20 to 24°C in a shipping box. In vitro PLT properties were evaluated on Day 1 (day after collection), after 5 and 7 days of storage. RESULTS: With both Amicus and Trima apheresis PLT units, the mean PLT content and concentration of CA and WCA were comparable and essentially constant throughout storage. Mean pH levels (±1 SD) after 5 days for Amicus apheresis PLT units were 6.97 ± 0.20 (WCA) and 7.13 ± 0.16 (p < 0.001, CA) and for Trima apheresis PLT units 6.97 ± 0.21 (WCA) and 7.22 ± 0.17 (p < 0.001, CA). In vitro variables, including percentage of disc PLTs, extent of shape change, and hypotonic stress levels, after 5 days of storage, showed mean differences between WCA and CA that were less than 15%. CONCLUSION: The in vitro results show that apheresis PLT units can be stored without agitation for 7 to 8 hours immediately after collection and also subsequently during storage for 24 hours with minimal influence on in vitro PLT properties compared to continuously agitated PLTs.     

Detection of bacterial contamination in apheresis platelet products: American Red Cross experience, 2004

BACKGROUND: Routine quality control (QC) testing for bacterial contamination in apheresis platelet (PLT) products was implemented in all 36 regional blood centers of the American Red Cross in March 2004. STUDY DESIGN AND METHODS: PLT samples were cultured under aerobic conditions until the end of the product shelf life or when a positive reaction was indicated. To confirm the initial positive reaction, a new sample was taken from the unit for reculturing. All positive culture bottles were referred for bacterial isolation and identification. Bacterial testing data along with apheresis PLT collection information were collected for analysis. Reports and investigations of potential septic reactions to apheresis PLTs were reviewed. RESULTS: In the first 10 months of bacterial testing, 226 of 350,658 collections tested initially positive. Sixty-eight were confirmed on resampling to be bacterially contaminated for an overall confirmed-positive rate of 0.019 percent or 1 in 5157. Staphylococcus spp. (47.1%) and Streptococcus spp. (26.5%) were the most frequently isolated bacteria; Gram-negative bacteria accounted for 17.6 percent of the confirmed-positive products. Of the 354 apheresis PLT products derived from all 226 initial test-positive cases, 38 (10.7%) were transfused by the time the initial positive reaction was indicated. None of these transfused products, however, had a confirmed-positive bacterial screen and no patient who had been transfused with an unconfirmed-positive product had evidence of a septic transfusion reaction. Three high-probability septic transfusion reactions to screened, negative components were identified. In all three cases, a coagulase-negative Staphylococcus was implicated. CONCLUSION: Our experience demonstrates that bacterial testing of apheresis PLT products as a QC measure was efficiently implemented throughout the American Red Cross system and that this new procedure has been effective in identifying and preventing the transfusion of many, although not all, bacterially contaminated PLT units.     

Canadian experience with detection of bacterial contamination in apheresis platelets

BACKGROUND: In Canada, both blood suppliers, Héma-Québec (HQ) and Canadian Blood Services (CBS), implemented bacterial testing in apheresis platelets (PLTs) with an automated microbial detection system (BacT/ALERT, bioMérieux). STUDY DESIGN AND METHODS: Validation of the BacT/ALERT Classic and 3D systems involved apheresis PLT spiking with different bacteria at concentrations of 10 and 10(2) colony-forming units per mL. As of February 2006, more than 95 percent of apheresis PLTs were screened for bacterial contamination at HQ and CBS. Between 3.5 and 10 mL of PLTs is inoculated into BacT/ALERT aerobic culture bottles followed by incubation for a maximum of 7 days. RESULTS: During the validation studies, all bacteria were detected at all concentrations and volumes tested. Upon implementation of bacterial screening, the percentage of initial positive samples at CBS and HQ was 0.09 and 0.07 percent, respectively. The rate of indeterminate cultures was significantly higher at CBS than at HQ, whereas the rates for true-positive, false-positive, and false-negative results did not differ significantly. Six confirmed-positive cultures, including three coagulase-negative staphylococci and three Enterobacteriaceae species, were detected and PLT units contaminated with these bacteria were not transfused. The rate of true-positive cultures was significantly lower than that reported by other blood operators. Unfortunately, failed detection of two contaminated units resulted in septic transfusion reactions. CONCLUSION: Bacterial screening of apheresis PLTs in Canada was successfully implemented, and transfusion of contaminated units was prevented. Rapid bacterial detection systems that could be used before transfusion, however, may further reduce the risk of transfusion reactions.     

Evaluation of in vitro storage properties of prestorage pooled whole blood–derived platelets suspended in 100 percent plasma and treated with amotosalen and long-wavelength ultraviolet light

BACKGROUND: Amotosalen, a psoralen, has been utilized for photochemical treatment (PCT) of apheresis platelets (PLTs) and pooled buffy coat PLTs suspended in additive solution. In the United States, the source of many PLT transfusions is from whole blood–derived PLTs prepared by the PLT‐rich plasma (PRP) method. This study investigated the in vitro PLT properties of amotosalen‐PCT of leukoreduced pools of PLTs prepared by the PRP method and suspended in 100 percent plasma. STUDY DESIGN AND METHODS: On Day 1 of storage, 12 leukoreduced (n = 6) or 10 leukoreplete (n = 6) ABO‐identical PLT concentrates were pooled, separated into two pools of 6 or 5 units, respectively, and leukoreduced (leukoreplete pools only). Each pool of 5 or 6 units was then photochemically treated (designated “test”: amotosalen plus 3.0 J/cm² long‐wavelength ultraviolet light followed by amotosalen/photoproduct removal) while the remaining identical pool (designated “control”) was untreated. PLT in vitro assays were performed on test and control pools during 7‐day storage. RESULTS: PCT resulted in slightly reduced pH in test pools compared to that of matched control pools after 5 days of storage (5‐unit pools: test, 6.96 ± 0.12 vs. control, 7.15 ± 0.09, p = 0.0033; 6‐unit pools: test, 6.90 ± 0.10 vs. control, 7.07 ± 0.09, p < 0.0001). Test pools adequately maintained many other in vitro properties including PLT morphology, hypotonic shock response, and extent of shape change parameters during 5‐day storage, which, like pH, also differed from those of controls. The pH of test and control pools declined on Day 7, with 1 of 6 test pools (either 5 or 6 units) having a pH value of less than 6.20, while all control pools had pH values of more than 6.66. CONCLUSION: PCT of leukoreduced PLT pools of whole blood–derived PLTs in 100 percent plasma maintained adequate PLT in vitro variables through 5 days of storage.     

A comparison of washed and volume‐reduced platelets with respect to platelet activation,aggregation, and plasma protein removal

BACKGROUND: Washed or volume‐reduced platelets (PLTs) are occasionally requested for patients with a history of allergic or anaphylactic transfusion reactions. However, conclusive data are not available as to which method is more suitable. STUDY DESIGN AND METHODS: A direct comparison of saline‐washed and volume‐reduced PLTs was performed by splitting 11 units of 6‐day‐old apheresis PLT units. PLT activation, aggregation, plasma protein, and PLT count were determined before and after each procedure. To assess whether washing using neutral, calcium‐free Ringer's acetate (NRA) would better preserve PLT function, 8 additional units of apheresis PLTs were split and were washed in saline or NRA. RESULTS: Saline washing resulted in significantly increased number of activated, P‐selectin–expressing PLTs compared to volume reduction (24.2% vs. 10.3%, p = 0.001). Aggregation was also significantly reduced (?40.6% vs. ?0.8%, p = 0.004). Plasma protein removal was significantly better for saline‐washed than volume‐reduced PLTs (96% vs. 51.1%, p < 0.001). PLT recovery was not significantly different for saline‐washed versus volume‐reduced PLTs (70.5% vs. 80.7%, p = 0.079). There was no difference between washing in saline or NRA with regard to PLT activation and loss of aggregation. CONCLUSIONS: PLT washing with saline or NRA significantly increases PLT activation and decreases PLT aggregability. On the other hand, volume reduction does not adequately remove plasma proteins. Therefore, PLT washing should be reserved for patients with a history of severe allergic or anaphylactic transfusion reactions. We suggest that fresher PLTs be selected to improve the functionality of washed PLTs.     

Quantitation of coated platelet potential during collection, storage, and transfusion of apheresis platelets

BACKGROUND: Coated platelets (PLTs), a subpopulation of PLTs observed upon dual agonist stimulation with collagen and thrombin, are known to retain several procoagulant α‐granule proteins on their surface. By formation of a highly active membrane‐bound prothrombinase complex, these PLTs represent an important step in the coagulation cascade as a consequence of their ability to generate thrombin at the site of vascular injury. Various clinical observations suggest that higher levels of coated PLTs are associated with thrombosis while a deficiency of coated PLTs results in a bleeding diathesis. Current quality control guidelines for in vitro PLT storage measure PLT viability but no routine evaluation of the hemostatic function of stored PLTs and particularly no estimation of coated PLT potential is performed. Our primary objective was to evaluate if the process of apheresis and storage of PLT units alters the levels of coated PLTs. In addition, we sought to determine how transfusion of stored PLTs into patients with thrombocytopenia affects the patient's coated PLT levels. STUDY DESIGN AND METHODS: Coated PLT levels were analyzed in 13 voluntary PLT donors before donation, in the fresh apheresis product (Trima, CaridianBCT) and in the stored apheresis product just before transfusion. In addition, 10 patients with thrombocytopenia were analyzed for coated PLTs before and after transfusion of a stored PLT product. RESULTS: Coated PLT levels were significantly decreased after the process of apheresis (17% relative decline; p < 0.01) and with prolonged storage (1 to 5 days; 53% relative decline; p < 0.001). Transfusion of stored PLT units did not result in significant increment of coated PLT levels in patients with thrombocytopenia as expected considering the low level of coated PLTs in stored PLT units. Furthermore, there was no suggestion of regeneration of coated PLT potential upon reinfusion. CONCLUSIONS: Isolation and storage of apheresis PLTs by standard blood bank procedures results in a significant decline in coated PLT potential. Reinfusion of stored apheresis PLTs into patients with thrombocytopenia resulted in a predictable change in coated PLT potential with no suggestion of regeneration of lost coated PLT potential.     

The role of bicarbonate in platelet additive solution for apheresis platelet concentrates stored with low residual plasma

BACKGROUND: Complex platelet additive solutions (PASs) are required to store platelet (PLT) concentrates with plasma levels below 30%. Previously, apheresis PLTs stored with 5% plasma in acetate‐ and bicarbonate‐containing PAS maintained stable pH and bicarbonate levels during 7‐day storage. Due to this observation, the necessity of added bicarbonate in PAS was investigated and whether the concurrent increase in PAS pH after bicarbonate addition had any effect on PLT storage. STUDY DESIGN AND METHODS: Apheresis PLTs were stored in 5% plasma‐95% high‐ or low‐pH PAS, with or without bicarbonate (n = 10 per arm). Bicarbonate PAS PLTs were paired and nonbicarbonate PAS PLTs were paired (split from same double‐dose collection). PLTs were evaluated for in vitro variables on Days 1 and 7 and up to Day 14 if the Day 7 pH was higher than 6.2. RESULTS: PLT pH was maintained above 7.3 to Day 14 in bicarbonate PAS PLTs while pH failures below 6.2 were observed in 4 of 10 and 2 of 10 units on Day 7 in low‐ and high‐pH nonbicarbonate PAS arms, respectively. Day 7 in vitro variables in nonbicarbonate PAS PLTs with pH values of higher than 6.2 were comparable to Day 7 variables in bicarbonate PAS PLTs. The pH of bicarbonate PAS did have a small effect on pH and bicarbonate levels in PLT units, but did not have an effect on functional variables and metabolism. CONCLUSION: Bicarbonate was not required to maintain in vitro PLT function in 5% plasma‐95% PAS, but was required as a pH buffer and increased PAS pH did not significantly contribute to this effect.     

Effects of storage duration and volume on the quality of leukoreduced apheresis‐derived platelets: implications for pediatric transfusion medicine

BACKGROUND: Platelet (PLT) storage adversely affects PLT structure and function in vitro and is associated with decreased PLT recovery and function in vivo. In pediatric transfusion medicine, it is not uncommon for small residual volumes to remain in parent units after aliquot preparation of leukoreduced apheresis‐derived PLTs (LR‐ADP). However, limited data exist regarding the impact of storage on residual small‐volume LR‐ADP. STUDY DESIGN AND METHODS: Standard metabolic testing was performed on residual volumes of LR‐ADP after aliquot removal and PLT aggregometry using a dual agonist of ADP and collagen was performed on stored, small‐volume aliquots (10‐80 mL) created from an in vitro model of PLT storage. RESULTS: Seventy‐seven LR‐ADP underwent metabolic (n = 67) or metabolic and aggregation (n = 10) studies. All products maintained a pH value of more than 6.89 throughout storage. Lactate and pCO₂ increased proportionally with longer storage time. Regardless of acceptable metabolism during storage, aggregation in 10‐ to 20‐mL aliquots was impaired by Day 4 and aliquots less than 40 mL demonstrated the most dramatic decrease in aggregation from baseline. CONCLUSIONS: Despite maintenance of acceptable metabolic conditions, residual volumes of LR‐ADP develop impaired aggregation in vitro that may adversely affect PLT survival and function in vivo. At volumes below 40 mL, LR‐ADP revealed reduced aggregation. As a result, it is recommended to monitor and record volumes of LR‐ADP used for pediatric transfusion. Moreover, once LR‐ADP attain a volume of 50 mL or less on Day 4 or Day 5 of storage, consider discarding these products until their in vivo efficacy can be studied.     

Platelet function under high-shear conditions from platelet concentrates

BACKGROUND: Platelet (PLT) collection and storage affect the functional capacity of PLTs in PLT concentrates (PCs). Therefore, PLTs' functional quality should be studied before transfusion. STUDY DESIGN AND METHODS: PCs (n = 15) were collected by a standard apheresis procedure (Trima, Gambro BCT) and were stored for 7 days. Samples were taken to assess PLT adhesion and aggregate formation by a cone and plate analyzer (Impact-R, DiaMed) on Days 1, 3, 5, and 7 after harvesting. This device allows testing PLT function under high-shear stress close to physiologic conditions. Concomitantly, P-selectin expression and the residual responsiveness to TRAP-6 were determined by flow cytometry. RESULTS: PLT adhesion, as measured by surface coverage, decreased during the entire observation period; likewise, the size of aggregates was significantly lower on Days 5 and 7 compared to Day 1 (p < 0.02). P-selectin expression increased from Day 5 to Day 7 (p < 0.04), whereas TRAP-6-inducible expression remained stable until Day 5 of storage and decreased significantly on Day 7 (p = 0.04). CONCLUSIONS: Our results show that high-shear-induced PLT adhesion and aggregation on the polystyrene surface deteriorate upon storage, suggesting decreased PLT function in vivo. Thus, the Impact-R may be a useful tool to assess the functional capacity of PLTs under various PLT harvesting and storage procedures.     

Longitudinal management with crossmatch‐compatible platelets for refractory patients: alloimmunization,response to transfusion,and clinical outcomes (CME)

BACKGROUND: The use of crossmatch‐compatible platelets (PLTs) improves posttransfusion corrected count increments (CCIs) in patients with alloimmune PLT refractoriness. However, few reports address the efficacy of utilizing this strategy for patients requiring intensive PLT transfusion therapy lasting several weeks to months. STUDY DESIGN AND METHODS: Medical records of patients with two or more PLT crossmatch assays performed between 2002 and 2010 were reviewed. All patients were refractory to random single‐donor apheresis PLT units, defined as two consecutive 1‐hour posttransfusion CCIs of less than 7500. A commercial solid‐phase adherence assay was used for crossmatching. RESULTS: Seventy‐one patients were included. A median of four crossmatch assays were performed per patient (range, 2‐17). Mean percent reactivity in initial (58.6%) versus last (55.3%) crossmatch assay for each patient demonstrated no trend toward progressive alloimmunization (p = NS). A total of 738 crossmatched PLT units were administered with a mean ± standard deviation CCI of 7000 ± 7900 (n = 443 units with adequate 1‐hr posttransfusion counts), a significant improvement over random PLTs (p < 0.001). Patients with an initial crossmatch reactivity of greater than 66% were significantly more likely to demonstrate at least one panreactive crossmatch assay, impacting the availability of compatible PLTs for optimum transfusion support. One patient (1.4%) developed WHO Grade IV bleeding. CONCLUSIONS: Progressive alloimmunization to mismatched antigens does not impact medium‐term transfusion support with crossmatched PLTs. Increased reactivity in the initial crossmatch assay can serve as a trigger to initiate workup for HLA‐matched PLTs as a second‐line approach. However, for most patients, medium‐term transfusion support with crossmatched PLTs offers an effective and rapid first‐line approach to management of PLT transfusion refractoriness.     

Platelet dose consistency and its effect on the number of platelet transfusions for support of thrombocytopenia: an analysis of the SPRINT trial of platelets photochemically treated with amotosalen HCl and ultraviolet A light

BACKGROUND: The SPRINT trial examined efficacy and safety of photochemically treated (PCT) platelets (PLTs). PCT PLTs were equivalent to untreated (control) PLTs for prevention of bleeding. Transfused PLT dose and corrected count increments (CIs), however, were lower and transfusion intervals were shorter for PCT PLTs, resulting in more PCT than control transfusions. PLT dose was analyzed to determine the impact of the number of PLTs transfused on transfusion requirements. STUDY DESIGN AND METHODS: Transfusion response was compared for patients with all doses of >or=3.0 x 10(11) and the complementary subset of patients with any dose of fewer than 3.0 x 10(11). Analyses included comparison of bleeding, number of PLT and red blood cell (RBC) transfusions, transfusion intervals, and CIs between PCT and control groups within each PLT dose subset. RESULTS: Mean PLT dose per transfusion in the PCT group was lower than in the control group (3.7 x 10(11) vs. 4.0 x 10(11); p<0.001). More PCT patients received PLT doses of fewer than 3.0 x 10(11) (n=190) than control patients (n=118; p<0.01). Comparisons of patients receiving comparable PLT doses showed no significant differences between PCT and control groups for bleeding or number of PLT or RBC transfusions; however, transfusion intervals and CIs were significantly better for the control group. CONCLUSIONS: When patients were supported with comparable doses of PCT or conventional PLTs, the mean number of PLT transfusions was similar. Lower CIs and shorter transfusion intervals for PCT PLTs suggest that some PLT injury may occur during PCT. This injury does not result in a detectable increase in bleeding, however.     

Apheresis donors and platelet function: inherent platelet responsiveness influences platelet quality

BACKGROUND: Process-induced platelet (PLT) activation occurs with all production methods, including apheresis. Recent studies have highlighted the range and consistence of interindividual variation in the PLT response, but little is known about the contribution of a donors' inherent PLT responsiveness to the activation state of the apheresis PLTs or the effect of frequent apheresis on donors' PLTs. STUDY DESIGN AND METHODS: The relationship between the donors' PLT response on the apheresis PLTs was studied in 47 individuals selected as having PLTs with inherently low, intermediate, or high responsiveness. Whole-blood flow cytometry was used to measure PLT activation (levels of bound fibrinogen) before donation and in the apheresis PLTs. The effects of regular apheresis on the activation status of donors' PLTs were studied by comparing the in vivo activation status of PLTs from apheresis (n = 349) and whole-blood donors (n = 157), before donation. The effect of apheresis per se on PLT activation was measured in 10 apheresis donors before and after donation. RESULTS: The level of PLT activation in the apheresis packs was generally higher than in the donor, and the most activated PLTs were from high-responder donors. There was no significant difference in PLT activation before donation between the apheresis and whole-blood donors (p = 0.697), and there was no consistent evidence of activation in the donors immediately after apheresis. CONCLUSION: The most activated apheresis PLTs were obtained from donors with more responsive PLTs. Regular apheresis, however, does not lead to PLT activation in the donors.     

Bacterial screening of apheresis platelets and the residual risk of septic transfusion reactions: the American Red Cross experience (2004-2006)

BACKGROUND: The American Red Cross initiated systemwide bacterial testing of all apheresis platelet (PLT) collections in March 2004, yet continues to receive reports of septic reactions after transfusion of screened components. STUDY DESIGN AND METHODS: The rates of confirmed bacterial contamination of apheresis PLT collections detected by prospective quality control (QC) testing, and by surveillance of reported septic reactions to screened-negative apheresis PLTs, were analyzed according to the technology utilized for collection. RESULTS: Between March 1, 2004, and May 31, 2006, bacterial culture testing was performed on 1,004,206 donations; of these, 186 (1:5,399) had confirmed-positive culture results. Transfusion of all but 1 of the associated 293 components was prevented. A significantly higher rate of confirmed-positive bacterial cultures was seen with products collected utilizing two-arm collection procedures compared to one-arm procedures (22.7 vs. 11.9 per 10(5) donations; odds ratio [OR], 1.9; 95% confidence interval [CI], 1.4-2.7). During this period, 20 septic transfusion reactions were reported, including 3 fatalities (1:498,711 fatalities per distributed component), which implicated screened-negative apheresis PLT products. The frequency of septic reactions was 4.7-fold higher for collections utilizing two-arm procedures (1:41,173; 95% CI, 1:25,000-1:66,667) compared to collections from one-arm procedures (1:193,305; 95% CI, 1:52,632-1:500,000; OR, 4.7; 95% CI, 1.2-18.4); most septic reactions (16 of 20) were due to Staphylococcus spp. and occurred on Day 5 (13 of 20) after collection. CONCLUSION: PLT contamination with bacteria that evade detection by QC culture remains a significant residual transfusion risk, in particular for older PLTs and skin-commensal bacteria in components collected by two-arm apheresis procedures during the study period.