I am the 9%: Making the case for whole-blood platelets

Platelet transfusions in adult ICU patients with thrombocytopenia: A sub-study of the PLOT-ICU inception cohort study

BACKGROUND

Platelet transfusions are frequently used in the intensive care unit (ICU), but current practices including used product types, volumes, doses and effects are unknown.

STUDY DESIGN AND METHODS

Sub-study of the inception cohort study 'Thrombocytopenia and Platelet Transfusions in the ICU (PLOT-ICU)', including acutely admitted, adult ICU patients with thrombocytopenia (platelet count <150 × 109/L). The primary outcome was the number of patients receiving platelet transfusion in ICU by product type. Secondary outcomes included platelet transfusion details, platelet increments, bleeding, other transfusions and mortality.

RESULTS

Amongst 504 patients with thrombocytopenia from 43 hospitals in 10 countries in Europe and the United States, 20.8% received 565 platelet transfusions; 61.0% received pooled products, 21.9% received apheresis products and 17.1% received both with a median of 2 (interquartile range 1-4) days from admission to first transfusion. The median volume per transfusion was 253 mL (180-308 mL) and pooled products accounted for 59.1% of transfusions, however, this varied across countries. Most centres (73.8%) used fixed dosing (medians ranging from 2.0 to 3.5 × 1011 platelets/transfusion) whilst some (mainly in France) used weight-based dosing (ranging from 0.5 to 0.7 × 1011 platelets per 10 kg body weight). The median platelet count increment for a single prophylactic platelet transfusion was 2 (-1 to 8) × 109/L. Outcomes of patients with thrombocytopenia who did and did not receive platelet transfusions varied.

CONCLUSIONS

Among acutely admitted, adult ICU patients with thrombocytopenia, 20.8% received platelet transfusions in ICU of whom most received pooled products, but considerable variation was observed in product type, volumes and doses across countries. Prophylactic platelet transfusions were associated with limited increases in platelet counts.

Expanding the platelet inventory to mitigate the impact of severe shortages

The platelet collection and distribution system, based on volunteer nonremunerated donors, apheresis platelet collections, and primarily 1-directional distribution of platelets for up to 5-day room temperature storage at hospitals, typically performs well and provides therapeutic support for hundreds of thousands of patients annually. However, direct and indirect effects of the coronavirus disease 2019 pandemic, particularly during the Omicron wave, produced dramatic systemic failures and severe shortages. We propose 4 initiatives to reinforce the existing platelet pipeline and buffer the platelet supply against future unexpected disruptions.

Evaluating apheresis platelets at reduced dose as a contingency measure for extreme shortages

BACKGROUND

The COVID19 pandemic highlights the need for contingency planning in the event of blood shortages. To increase platelet supply, we assessed the operational impact and effect on platelet quality of splitting units prior to storage.

STUDY DESIGN AND METHODS

Using production figures, we modeled the impact on unit numbers, platelet counts, and volumes of splitting only apheresis double donations into three units (yielding ⅔ doses), or all standard dose units in half. To assess quality, eight pools of three ABO/Rh-matched apheresis (Trima Accel) double donations in plasma were split to ⅔ and ½ volumes in both Terumo and Fresenius storage bags. These were irradiated and subject to maximal permitted periods of nonagitation (3 × 8 h) before comparing platelet quality markers (including pH, CD62P expression) to Day 9 of storage.

RESULTS

Splitting all double donations into three predicted inventory expansion of 23% overall whereas halving all standard dose units clearly doubles stock. In our study, ⅔ and ½ doses contained 153 ± 15 × 10⁹ (~138 ml) and 113 ± 11 × 10⁹ (~102 ml) platelets respectively. Following storage, higher pH was observed in ⅔ than in ½ doses and in Terumo compared to Fresenius bags. The higher pH was reflected in better quality markers, including lower CD62P expression. Despite the differences, on Day 8 (of pH monitoring at expiry) all ⅔ doses and most ½ doses were ≥pH 6.4.

CONCLUSION

A strategy to split apheresis platelets in plasma to lower doses is feasible, maintains acceptable platelet quality, and should be considered by blood services in response to extreme shortages.

Hemostatic Resuscitation in Children

Trauma is a major source of morbidity and mortality for children worldwide; life-threatening hemorrhage is a primary cause of preventable death. Essential interventions in children with life-threatening hemorrhage include hemostatic resuscitation and mechanical control of bleeding. Herein we review pediatric hemostatic resuscitation, a strategy that addresses both hemorrhagic shock and the coagulopathic complications described in patients with major hemorrhage. Some components of hemostatic resuscitation may include: early and aggressive resuscitation with blood products, minimizing crystalloid and hemodilution, antifibrinolytic adjuncts such as tranexamic acid, and the novel use of low-titer group O whole-blood (LTOWB) transfusion in injured children. The following selection of important publications address the current state of hemostatic resuscitation strategies in pediatric trauma patients as well as the remaining knowledge gaps and areas for further research.

A Comparison of Transfusion-Related Adverse Reactions Among Apheresis Platelets, Whole Blood-Derived Platelets, and Platelets Subjected to Pathogen Reduction Technology as Reported to the National Healthcare Safety Network Hemovigilance Module

Despite advances in transfusion safety, concerns with safety of platelet transfusions remain including platelet-related sepsis and higher reaction rates observed among patients receiving apheresis platelets (APLTs). National Healthcare Safety Network (NHSN) Hemovigilance Module (HM) data were analyzed to quantify the burden and severity of adverse reactions occurring from APLTs and whole blood-derived platelets (WBD-PLTs). Facilities participating in NHSN HM during 2010-2018 were included. Adverse reaction rates (number per 100,000 components transfused) were calculated for APLTs and WBD-PLTs stratified by severity, use of platelet additive solution (PAS), and pathogen reduction technology (PRT). Chi-square tests were used to compare rates. During the study interval, 2,000,589 platelets were transfused: 1,435,154 APLTs; 525,902 WBD-PLTs; and among APLTs, 39,533 PRT-APLTs. APLT adverse reaction rates were higher (478 vs 70/ 100,000, P< .01) and more often serious (34 vs 6/100,000; P< .01) compared with WBD-PLTs. Adverse reactions were higher among PRT-APLTs (572/100,000) and were less often serious (18/100,000) compared with non-PRT-APLTs (35/100,000) although this association was not statistically significant. Among components implicated in adverse reactions, 92% of APLTs were suspended in plasma. Compared with PRT-APLTs stored in PAS, rates were higher among units stored in plasma (760 vs 525/100,000). Most serious reactions (75%) were allergic. No transfusion-transmitted infections were reported among PRT-APLTs. APLTs were associated with a 6-fold and 2-fold higher serious adverse reaction risks compared with WBD-PLTs and PRT-APLTs, respectively. These findings demonstrate the importance of monitoring transfusion-related adverse reactions to track the safety of platelet transfusions and quantify the impact of mitigation strategies through national hemovigilance systems.

Rhesus D Antigenic Determinants on Residual Red Blood Cells in Apheresis and Buffy Coat Platelet Concentrates

BACKGROUND

The level of residual red blood cells (RBCs) in platelet concentrates (PCs) is of interest because of clinical concerns related to alloimmunization to RBC antigens in transfused patients. This work aims at characterizing and quantifying the levels of intact and fragmented RBCs in apheresis (AP-PCs) and buffy coat PCs (BC-PCs) to assess their potential risk for RhD antigen alloimmunization.

METHODS

After staining with anti-CD41 (platelets) and anti-CD235a (RBCs) antibodies, the size and density of RhD antigen on intact and fragmented RBCs were analyzed by flow cytometry.

RESULTS

Residual RBC counts were 29 ± 22 × 106/unit in AP-PCs and 121 ± 54 × 106/unit in BC-PCs, which correspond to about 3 and 11 µL of RBCs by product, respectively. RhD expression was about 4 times higher on RBC particles in AP-PCs, and these particles contribute to 66 and 75% of the total antigenic load in BC-PCs and AP-PCs, respectively.

CONCLUSIONS

Processing methods influence the quantity and nature of contaminating residual RBCs and RBC-derived particles in PCs. The estimation of residual RBCs in these blood products is generally based on measurements of intact RBCs, which might underestimate the risk for alloim-munization in transfused patients. The question of whether these RBC-derived particles can produce an immune response and, thus, should then be taken into consideration for Rh immune prophylactic treatments, remains to be clarified.

Response to random apheresis platelets versus HLA-selected platelets versus pooled platelets in HLA-sensitized patients

BACKGROUND

It is unknown how pooled platelets (PPs) compare to random apheresis platelets (RAPs) when HLA-selected platelets (PLTs) are unavailable for HLA-sensitized patients. The aim of this study was to compare patient responses to RAPs, HLA-selected PLTs, and PPs in HLA-sensitized patients.

STUDY DESIGN AND METHODS

This is a single-institution retrospective study of patients from January 2014 to April 2017 with a class I calculated panel-reactive antibody of 60% or more. Response to transfusion was determined by a corrected count increment (CCI) up to 1 hour after completion of transfusion. A CCI of 5 or more was considered successful.

RESULTS

Seventy-seven units of RAPs, 412 units of HLA-selected PLT, and 388 units PPs were transfused. Mean CCIs when transfusing RAPs, HLA-selected PLTs, and PPs were 2.82, 11.44, and 4.77, respectively (p < 0.0001). Posttest comparison between RAPs and PPs revealed no significant difference in mean CCI while there was a significant difference between HLA-selected PLTs versus RAPs and HLA-selected PLTs versus PPs. The success rates of RAPs, HLA-selected PLTs, and PPs were 31%, 80%, and 35% respectively. There was no significant association of type of PLT and success rate when comparing RAPs versus PPs (p = 0.51) while there was a significant association between success rate and type of PLT transfusion when comparing HLA-selected PLTs with RAPs and PPs.

CONCLUSION

HLA-selected PLTs resulted in higher mean CCIs and more successful transfusions. There was no significant difference in mean CCI or success rate when transfusing RAPs versus PPs to HLA-sensitized patients. Future studies should assess clinical outcomes in HLA-sensitized patients receiving each type of PLT product.

Predisposing factors for anti-D immune response in D- patients with chronic liver disease transfused with D+ platelet concentrates

BACKGROUND

Recent reports have indicated that the risk of anti-D alloimmunization following D-incompatible platelet (PLT) transfusion is low in hematology and oncology patients. We investigated the rate of anti-D alloimmunization in RhD-negative (D^- ) patients with chronic liver disease transfused with D⁺ platelet concentrates (PCs) and the factors involved, at a liver transplant (LT) center.

STUDY DESIGN AND METHODS

We reviewed the blood bank database from January 2003 to October 2016. D^- patients who had received D⁺ PLT transfusions were eligible if they had undergone antibody screening at least 28 days after the first D⁺ PC transfusion, had no previous or concomitant exposure to D⁺ blood products, and had not received anti-D immunoglobulins.

RESULTS

Six of the 56 eligible patients (10.7%) had anti-D antibodies. All had received whole blood-derived PCs. Four of 20 patients (20%) untransplanted or transfused before LT and only two of 36 patients (5.6%) transfused during or after LT produced anti-D antibodies. These two patients were on maintenance immunosuppression based on low-dose steroids and tacrolimus. The factors identified as significantly associated with anti-D immune response were the presence of red blood cell immune alloantibodies before D⁺ PLT transfusion (p = 0.003), and D⁺ PLT transfusion outside the operative and postoperative (5 days) periods for LT (p = 0.023).

CONCLUSION

D^- patients with chronic liver disease transfused with D⁺ PLTs before LT are at high risk of developing anti-D antibodies. Preventive measures should be considered for these patients.

Platelet Transfusion Induces Alloimmunization to D and Non-D Rhesus Antigens

Background

Platelet concentrates (PC) contain residual contaminating red blood cells (RBC), being higher in pooled buffy coat PC (BC-PC) than in apheresis units (AP-PC). Data about PC-induced alloimmunization against non-D Rhesus (Rh) antigens are limited.

Methods

For all newly detected RhD and non-D alloantibodies between August 2015 and September /2017 we prospectively evaluated if they were triggered through PC by analyzing for incompatible RBC and/or PC transfusions.

Results

We found 5,799 positive results in 89,190 antibody screening tests. We identified 13 newly detectable Rh antibodies through incompatible PCs in 11 patients: 6× anti-D, 4× anti-E, 2× anti-c, 1× anti-f. They received a total of 156 PC (83 BC-PC; 73 AP-PC): 5 patients received incompatible BC-PC only, 1 patient received incompatible AP-PC only, 5 patients received incompatible BC-PC and AP-PC. Quality control showed a mean (range) of 0.304 (0.152-1.662) and 0.014 (0.003-0.080) × 10⁹ RBC/l for BC-PC and AP-PC, respectively. Ten of the 11 patients received RBC transfusions, all of them being antigen-negative for the alloantibodies identified.

Conclusions

PC transfusions may not only induce RhD alloimmunization, but also immunization against further Rh antigens such as c, E, and f. The risk seems higher for BC-PC than for AP-PC. The results may have impact on future recommendations of PC transfusion with respect to Rh compatibility and upper limits of RBC contamination.