Corrected Count Increment Research Articles

Utility of acid citrate dextrose‐acidification for platelet volume reduction protocols in the transfusion service

AbstractBackgroundVolume‐reduced platelets can minimize circulatory overload, allergic transfusion reactions, or out‐of‐group plasma infusion. Our center adopted a volume reduction protocol that includes acidification with acid citrate dextrose solution A (ACD‐A) before centrifugation and without any rest period prior to resuspension allowing a better turnaround time for platelet issue.Study Design and MethodsThis report compares corrected count increments (CCIs) from full‐volume and ACD‐A acidified volume‐reduced human platelets in a retrospective study at a single hospital and in a mouse model.ResultsAt a pediatric tertiary care hospital, 530 patients received conventional apheresis platelets during the 20‐month study period. Among all patients, the expected 4‐h mean CCI was 9.8 (95% CI: 8.7, 10.9) for full‐volume platelets, and 8.8 (95% CI: 7.3, 10.6) for ACD‐acidified volume‐reduced platelets (p = .29). A statistically significant difference (p = .01) was identified in the expected 24‐h mean CCI: 6.3 (95% CI: 5.5–7.0) with full‐volume platelet, 4.7 (95% CI: 3.6–6.0) with ACD‐acidified volume‐reduced platelet. Limiting CCI calculations to patients with Hematology/Oncology/Hematopoietic Progenitor Cell Transplant diagnosis (n = 296, 56%) indicated a statistically significant difference in both 4‐ and 24‐h predicted CCIs, showing lower CCIs in ACD‐acidified volume‐reduced platelet, although these were still similar to the CCIs observed in all patients and considered to be clinically acceptable responses similar to other volume reduction protocols. The recovery of count‐adjusted, volume‐reduced platelets was significantly lower in mice, suggesting a procedure‐related defect.DiscussionACD‐A acidification of platelets before volume reduction decreases turnaround time for platelet issue and provides clinically allowable 4‐h and 24‐h platelet increments.

Splitting apheresis platelets as a contingency measure for inventory shortages.

Splitting apheresis platelet (PLT) units increase available inventory during shortages. The impact of prolonged storage in gas-impermeable aliquot bags on PLT quality in vitro and transfusion outcomes in patients remains uncertain. We assessed in vitro PLT quality and thromboelastography (TEG) in PLTs stored for 8 or 24 h in aliquot bags compared with baseline (T0). Retrospective assessment of response (PLT increment and corrected count increment (CCI)) was conducted among adults (≥18 years) transfused with split platelet units from January 2021 to June 2022. No differences were observed in PLT and white blood cell (WBC) counts, mean platelet volume, or TEG parameters during storage, except for an increase in TEG R time (mean ± SD) at 24 h (6.1 ± 0.5 min) compared to T0 (4.4 ± 0.8 min), p = 0.0031 one-way ANOVA. Eighty-one patients were transfused 119 split units with a median [IQR] PLT yield of 2.1 × 1011[1.9 × 1011 to 2.3 × 1011] and storage duration of 1.6[0.7-9.1] h. The overall median PLT count increment was 6.0 × 103/uL and CCI was 5.0 × 103, correlating negatively with split unit storage duration (Spearman rho = -0.218, p = 0.017). Compared with split transfusions of pathogen-reduced (PR) PLTs, non-PR splits were associated with higher median platelet count increments (7.0 × 103/μL vs. 4.0 × 103/μL, p = 0.0263 Mann-Whitney U) and higher CCIs (6.5 × 103 vs. 3.9 × 103, p = 0.0116 Mann-Whitney U) despite no differences in PLT yields (2.1 × 1011/μL vs. 2.1 × 1011/μL). Storing PLTs in aliquot bags for 8 or 24 h does not adversely affect their quality in vitro. Splitting apheresis PLTs are feasible for adult transfusions during shortages. It may be advisable to prioritize non-PR PLTs for splitting given improved patient responses.

Analysis of platelet transfusion efficacy during extracorporeal membrane oxygenation (ECMO) treatment in pediatric patients post-cardiac surgery-a retrospective cohort study.

Postoperative extracorporeal membrane oxygenation (ECMO) may be necessary for pediatric patients following cardiac surgery, with associated risks of thrombocytopenia and bleeding. Prophylactic platelet transfusions are utilized to mitigate these risks, but the effectiveness of platelet transfusion cannot be reliably predicted. The aim of this study was to investigate the effect of platelet transfusion during postoperative treatment with ECMO in children undergoing cardiac surgery and to explore the optimal transfusion thresholds to reduce the number of platelet transfusions in patients and reduce the risk of death. We included in our study patients from the Pediatric Cardiac Surgery Department at the First Affiliated Hospital of Tsinghua University who underwent cardiac surgery and received ECMO treatment from January 1, 2019, to December 31, 2023, and received platelets transfusion at least once during the ECMO therapy. The platelet counts were determined both before and 24 hours posttransfusion of the platelet product. The corrected count increment (CCI) was calculated for the effectiveness estimation of platelet transfusion. The research subjects were divided into 3 groups based on the platelet count before transfusion (pretransfusion platelet count ≤30×109/L was the low-threshold group, pretransfusion count 31-50×109/L was the medium-threshold group, and ≥51×109/L was the high-threshold group) and the effective rates of each group were calculated. A total of 11 patients received 47 platelet transfusions, an average of 4.27 ± 1.67 per patient. According to the 24-hour postinfusion platelet (Plt) corrected critical control increase index (24-hour CCI) ≥4500, the infusion was considered to be effective, and ineffective when the CCI was <4500. Out of these, 22 transfusions (46.8%) proved effective, whereas 25 (53.2%) were deemed ineffective. The effective transfusion rates across the 3 groups were 69.2%, 50%, and 27.7%, respectively. The efficacy of platelet transfusion may be higher if a low threshold of platelet transfusion is chosen during ECMO treatment, on the premise of ensuring life safety.

Effect of platelet storage duration on platelet increment and clinical outcomes in critically ill patients - a randomised controlled trial.

Platelet storage duration may influence transfusion effectiveness and patient outcomes.The present study aimed to evaluate the effect of platelet storage duration on platelet increment and clinical outcomes in patients admitted to the intensive care unit (ICU). This prospective, open-label, randomized controlled trial, conducted at a single centre, enrolled ICU patients requiring platelet transfusion. Patients were randomly assigned to receive platelet concentrates aged ≤3 days (Group 1) or 4-5 days (Group 2). Platelet increments were assessed by Absolute Platelet Count Increment (ACI), Corrected Count Increment (CCI), and Percentage Platelet Recovery (PPR). Clinical outcomes including bleeding, infection rates, ICU stay, red cell transfusion requirements, and mortality were also monitored. Patients transfused fresher platelets (Group 1) had higher median ACI, CCI and PPR at 1 hour compared to those transfused older platelets (Group 2) though the difference was not statistically significant.At 24 hours, Group 1 patients had a median ACI of 28,000/µl compared to 14,000/µl in Group 2(p = 0.001). The median CCI was 16,800 in Group 1 versus 8,200in Group 2(p = 0.001). Group 1 also had a higher median PPR of 45.7% compared to 23.6% in Group 2(p = 0.011).There was no significant difference in clinical outcomes such as bleeding, infection rates, ICU stay, or mortality between the groups. Multivariate analysis indicated that co-morbidities and higher APACHE-III score were associated with increased mortality. Transfusion of fresher platelets resulted in higher increments and transfusion effectiveness but did not affect clinical outcomes or mortality. Trial registration details: Clinical Trials Registry of India (CTRI/2023/03/050676).

Cumulative donor-specific antibody threshold predicts platelet transfusion response in HLA-alloimmunized patients

AbstractUp to a third of patients with hemato-oncologic conditions who have received multiply transfusions develop immune-mediated platelet transfusion refractoriness. Yet factors that influence posttransfusion platelet corrected count increments (CCI) in patients with HLA-alloimmune platelet transfusion refractoriness remain less well elucidated. Recent advances in HLA antibody characterization using fluorescent bead-based platforms enable the study of donor-specific antibody (DSA) avidity (as measured by mean fluorescence intensity [MFI]) and its impact on HLA-alloimmune platelet transfusion refractoriness. In this large retrospective study of 2012 platelet transfusions among 73 HLA-alloimmunized patients, we evaluated the impact of cumulative HLA DSA-MFI alongside other donor, platelet component, and patient characteristics on CCI at 2 and 24 hours after transfusion. As part of a quality improvement initiative, we also developed and tested a computerized algorithm to optimize donor–recipient histocompatibility based on cumulative DSA-MFI and sought other actionable predictors of CCI. In multivariate analyses, cumulative HLA DSA-MFI of ≥10 000, major/bidirectional ABO-mismatch, splenomegaly, transfusion reactions, and platelet storage in additive solution negatively affected 2-hour but not 24-hour posttransfusion CCI. The DSA-MFI threshold of 10 000 was corroborated by greater antibody-mediated complement activation and significantly more CCI failures above this threshold, suggesting the usefulness of this value to inform “permissive platelet mismatching” and to optimize CCI. Furthermore, DSA-MFI decreases were deemed feasible by the computer-based algorithm for HLA-platelet selection in a pilot cohort of 8 patients (122 transfusions) evaluated before and after algorithm implementation. When HLA-selected platelets are unavailable, ABO-identical/minor-mismatched platelet concentrates may enhance 2-hour CCI in heavily HLA-alloimmunized patients with platelet transfusion refractoriness.

Improving platelet function following prophylactic platelet transfusion in patients with hematological malignancies.

Platelet transfusion is a standard treatment to prevent bleeding in patients with hematological malignancies. Although transfusions can improve platelet count, their impact on platelet function remains controversial. We conducted flow cytometry to assess platelet function before and after transfusion and performed subgroup analyses to examine differences based on blood type, corrected count increment (CCI), and platelet microparticles. Overall, 50 patients who received prophylactic platelet transfusion were enrolled. CD42b expression increased, whereas CD41 expression decreased after transfusion. Apheresis platelets exhibited the lowest expression of PAC-1 and P-selectin when exposed to agonist stimulations. PAC-1 expression increased under high adenosine diphosphate (ADP) stimulation, while P-selectin expression increased under both high ADP and thrombin receptor-activating peptide stimulation. In the subgroup analysis, patients with a CCI >4500 and those with the same blood types exhibited a more significant increase in PAC-1 and P-selectin expression under agonist stimulation. When comparing apheresis platelets collected on different days, only the percentage of platelet-derived microparticles showed a significantincrease. Prophylactic transfusion improved platelet function. Platelet function significantly improved in patients with a CCI >4500, those with the same blood types as that of apheresis platelets, or those with platelet-derived microparticle levels <4.7%. No significant improvement in platelet function was noted after the transfusion of different blood types with acceptable compatibility or the transfusion of incompatible blood types. Our results suggest that transfusing platelets with the same blood type remains the optimal choice.

Comparison of platelet transfusion effectiveness between Helicobacter pylori-positive and -negative immune thrombocytopenia.

Immune thrombocytopenia (ITP) is characterized by early platelet destruction and impaired platelet production. Helicobacter pylori (H. pylori) infection seems to contribute to the pathogenesis in certain ITP patients in Japan. We compared the effectiveness of platelet transfusion in severe ITP in the presence or absence of H.pylori. The median corrected count increment (CCI) at 24 h after platelet transfusion (CCI-24) of the H.pylori-positive ITP patients was higher than that of the H. pylori-negative ITP patients (6463 vs. 754, p < 0.001), and the CCI-1 was also in the same direction but not significant (23 351 vs. 11 578). Multiple regression analyses showed that H. pylori infection was independently associated with CCI-24. Our study suggests that platelet transfusion may be more effective in H. pylori-positive ITP patients.

Response to apheretic platelet transfusion in children of acute lymphoblastic leukemia receiving induction chemotherapy: a cross-sectional study from Bangladesh.

Disease and therapy-related hypoproliferative thrombocytopenia is a significant barrier to managing acute lymphoblastic leukaemia (ALL) patients. To reduce the risk of haemorrhage, apheretic platelet transfusion is a modern, effective, and expensive option. Since most ALL patients in Bangladesh have financial constraints, this study can shed light on the magnitude of benefit regarding the effectiveness of apheretic platelet prophylactically and therapeutically in children of ALL receiving induction chemotherapy. This observational cross-sectional study was conducted in the department of transfusion medicine and the department of paediatric haematology and oncology at a tertiary level hospital in Bangladesh from June 2020 to June 2021. A total of 33 cases of ALL were enroled in this study according to inclusion and exclusion criteria. After receiving written informed consent, relevant data were collected using a face-to-face interview with the guardian of the patients, thorough clinical examination, and relevant investigation. After the collection of all the required data, analysis was done by Stata (v.16). Mean age of the patients was 7.39±4.46 (SD), ranging from 1 to 18 years. The majority of children were aged younger than or equal to 10 years (69.70%). Male children were slightly predominant (51.5%). Significant post-transfusion platelet increment (Median pre-transfusion count 16×103/μl vs. Median post-transfusion count 133×103/μl, P<0.001) was observed. WHO bleeding grades also improved after apheretic platelet transfusion (P<0.05). Age was a significant factor associated with corrected count increment (CCI) in both univariate and multivariate analysis. In subgroup analysis, age and gender were significant predictors of CCI in therapeutic transfusion group but not in prophylactic transfusion group. Significant improvement in bleeding status and platelet count was observed following apheretic platelet transfusion.

Establish a Graded Method to Avoid HLA Class I Antibodies Corresponding Antigen and Combining HLAMatchmaker Application in Improving the CCI Value after Platelet Transfusion for Patients with IPTR

To establish a graded method to avoid mean fluorescence intensity (MFI) threshold of HLA Class I antibodies corresponding antigen, and the HLAMatchmaker program has been used to select the minimum mismatch value of donor-patient epitopes. Evaluate the application value of combining both methods in selecting HLA compatible platelets (PTL) for patients with immune platelet transfusion failure (IPTR) in improving platelet the corrected count increment (CCI). A total 7 807 PLT cross-matching compatible were performed by the solid-phase red cell adherence (SPRCA) method for 51 IPTR patients. The Luminex single antigen flow cytometry was used to detect HLA Class I antibodies in patients, and detected the MFI value for different specificity antigens of HLA Class I antibodies, was graded into strong positive group (MFI>4 000, level 1), medium positive group (1 000< MFI≤4 000, 2), weak positive group (500< MFI≤1 000, 3), and one negative control group (MFI≤500). The results of 7 807 SPRCA their negative/positive reaction wells were enrolled and statistically analyzed in different grades and the four groups, the statistical differences between the four groups were compared. Multiple applications for the select HLA Class I compatible donor events were made for patients in two cases, and HLAMatchmaker program was used to calculate the number of HLA Class I epitopes mismatches between the donors and patients. The donor with the minimum number of epitopes mismatches was selected, while avoiding the corresponding antigens of HLA Class I antibodies in levels 1 and 2, the provision of HLA compatible platelets for IPTR. After the transfusions, the CCI value of the platelet transfusion efficacy evaluation index was calculated, and the clinical evaluation of the transfusion effect was obtained through statistical analysis. There were statistically significant differences in the positive results of SPRCA immunoassay among the strong positive group, medium positive group, and weak positive group of 51 IPTR patients with different specific of HLA -I class antibodies and corresponding antigens(all P <0.001). The positive results showed a range from high to low, with strong positive group>medium positive group>weak positive group. There were a statistical difference among between the strongly positive or moderately positive groups and the negative control group(P <0.001). There was no statistical difference between the weakly positive group and the negative control group(P >0.05). The strong positive group was set as the corresponding specific HLA Class I site corresponding antigen grade 1 avoidance threshold, the medium positive group as the grade 2 avoidance thresholds, and the weak positive group as the grade 3 avoidance threshold. In the case of donor platelet shortage, it is not necessary to avoid the weak positive group. Avoiding the strategy of donor antigens and HLAMatchmaker program scores ≤7 corresponding to HLA Class I antibodies of levels 1 and 2, with CCI values>4.5×109/L within 24 hours, can obtain effective clinical platelet transfusion conclusions. When selecting HLA Class I compatible donors for IPTR patients, the grading avoids HLA Class I antibodies corresponding to donor antigens, and the donor selection strategy with the minimum scores of HLAMatchmaker program is comprehensively selected. The negative result confirmed by platelet cross-matching experiments has certain practical application value for improving platelet count in IPTR patients.

Assessment of Platelet Crossmatch Results by Solid Phase Red Cell Adherence Assay among Pediatric Hemato-oncology Patients in a Tertiary Care Oncology Center

ABSTRACT Background and Objectives: This study employed platelets cross-matched by the solid-phase red cell adherence (SPRCA) method and oc-related it with posttransfusion platelet count increment in terms of corrected count increment (CCI) and percent platelet recovery (PPR) among pediatric hemato-oncology patients. It did not study subgroups of patients nor did it have a control group. This was an observational study. The objective of the study was to assess platelet crossmatch results by the SPRCA method and find its correlation with posttransfusion platelet count increment among pediatric hemato-oncology patients in a tertiary care oncology center. Methods: This was a prospective observational study performed on pediatric patients with hematological malignancies requiring platelet transfusions during August 2019–January 2020. An assessment of the response to platelet transfusion on the participants was analyzed against the crossmatch results using SPRCA to measure the response in terms of CCI and PPR. Results: A total of 80 pediatric multiply transfused patients of hematological malignancies were transfused with ABO-identical single donor platelet unit which was subsequently tested for compatibility SPRCA assay. Among a total of 80 platelet crossmatches, 86% (69/80) were found to be compatible. Among 69 patients with compatible platelet crossmatches, 91% (63/69) had adequate CCI (&gt;7500). Among 11 patients with incompatible crossmatches, 73% (8/11) had adequate CCI, and 27% (3/11) had inadequate CCI. Statistically significant association was found between crossmatch compatibility and PPR. Conclusions: Transfusion of crossmatched platelets from the available inventory to multiply transfused patients of hematological malignancies can be an option. It is very important to assess the posttransfusion platelet responses in such patients in terms of CCI as well as PPR. The SPRCA assay is a rapid and effective method to select the compatible unit from the inventory and is feasible to implement in an oncology setup to cater the requirement of multiple platelet transfusions to patients with hematological malignancies.

Donor-Specific Antibody Mean Fluorescence Intensity Threshold Predicts Platelet Transfusion Response in HLA-Alloimmunized Patients

Introduction:Patients with platelet transfusion refractoriness (PTR) due to HLA-alloimmunization respond to HLA-matched platelets. However, 4/4 HLA-matched platelets or platelets without donor-recipient antigenic mismatches are rarely available. Further, in severe HLA-alloimmunization, it is difficult to find donor products which do not contain antigens to which the recipient has developed antibodies ( i.e. antibody specificity prediction, ASP method). Hence, studies have evaluated platelet transfusion responsiveness in the presence of ≥1 donor specific antibodies (DSAs) to widen donor pools, a strategy termed permissive mismatching (PERMM). Using established semi-quantitative techniques for HLA-antibody detection, we sought to identify a cumulative DSA threshold which predicted platelet corrected count increment (CCI) failure despite PERMM. Methods:We retrospectively reviewed platelet transfusions among patients with HLA-alloimmunization and suspected PTR at the University of Washington/Fred Hutchinson Cancer Center from 2021-2023. HLA Class I antibodies were detected using a solid-phase single antigen bead assay (One Lambda) on the Luminex platform with individual antibody strengths measured by the mean fluorescence intensity (MFI). The calculated panel reactive antibodies (cPRA) were defined as the proportion of donors against whom recipients had antibodies. Transfusions were categorized as HLA matched, PERMM (DSA MFI&amp;gt;0), or random donor platelets (HLA-type unknown). CCI was calculated as described by Cohn ASH 2020. Results: Of 420 patients suspected to have PTR, 75 had cPRA &amp;gt; 50% and received ≥3 HLA-selected platelet transfusions. Of the 2726 transfusions these patients received, 1198 were excluded due to unavailability of post-transfusion platelet counts within 2 hours or due to multiple transfusions occurring between platelet counts. Ultimately, 1528 transfusions were analyzed (Panel A). In 1031 PERMM transfusions, the cumulative MFI was a stronger predictor of CCI at 2 hours than cPRA or the number of mismatched DSA (coefficients of determination or R2 of 7.3%, 2%, and 0.4%, respectively). We then examined the spectrum of cumulative MFIs to identify a threshold MFI predicting transfusion success/failure among the PERMM products. PERMM platelet transfusions in recipients with DSA MFIs of up to 5000 generated CCIs similar to HLA-matched platelets. However, CCI was significantly different between MFI &amp;lt;10,000 (median CCI 17,783) and MFI ≥10,000 (median CCI 3753) (Panel B). We then stratified data by splenomegaly, a significant non-immunologic cause of PTR (23.2% of transfusions, R2 15.8% for CCI prediction). Of the transfusions not affected by splenomegaly, 9.6% did not generate an adequate platelet response (defined as a CCI &amp;gt;5000) across all MFIs. This failure rate increased to 33.3%, 40.8%, and 52.8% among transfusions in recipients with MFIs &amp;gt;5000, &amp;gt;7500, and &amp;gt;10,000, respectively. After multiple testing correction, MFI of several individual DSAs (A1, A2, A24, A68, B8, B37, B39, B44, B51, B57, and B62) were also found to be significant predictors of CCI using linear regression ( n ranging 32-193, R2 ranging 6-33%). Conclusions: This is the largest study to date evaluating optimal MFI thresholds of DSAs for permissive HLA mismatching in the context of platelet transfusions. Cumulative DSA MFIs demonstrated a dose response effect with lower MFIs generating better CCIs. In our patient cohort overall, and when stratified by splenomegaly, we identified a threshold for cumulative DSA MFIs of 10,000, under which &amp;gt;50% of transfusions resulted in an adequate CCI. This MFI threshold (&amp;gt;10,000) has been implicated in HLA mismatched solid organ transplant rejections (Kallon, Transf. Med. 2020) as well as in a pooled analysis of smaller HLA-selected platelet transfusion studies conducted by our group (unpublished). If incorporated into a transfusion strategy, this MFI threshold may perform better than units chosen based on the number of mismatched DSAs alone or random donor platelets and widen the donor pool. Identifying the impact of specific HLA antibodies on CCIs needs further study. Studies are also underway to correlate cumulative DSA MFIs with complement activation (C1q levels) as a possible mechanistic explanation for the differences noted across the MFI threshold of 10,000 in our study.

Impact of Non-Immune Factors on Platelet Transfusion Responses in an Allo-Immunized Cohort

Background: Patients with hematologic malignancies and/or hematopoietic stem cell transplantation (HSCT) recipients often require platelet transfusion support for extended periods. This can result in platelet transfusion refractoriness (PTR) from HLA alloimmunization in up to 30% of individuals. These medically complex patients may also have splenomegaly, fevers and other factors which contribute to PTR. Consequently, they may demonstrate variability in immediate platelet recovery (at 0-2 hours post-transfusion), and in subsequent platelet consumption (at 18-24 hours) despite receiving HLA-selected platelet products. We sought to examine patient and product related factors which impacted platelet transfusion response in a cohort of HLA-alloimmunized platelet transfusion refractory patients. Methods: From April 2021 to June 2023, HLA-alloimmunized (PRA &amp;gt;50%) subjects who required three or more HLA selected platelet units were identified at the Fred Hutchinson Cancer Center/University of Washington. Data were obtained on patient demographics, diagnoses, Panel Reactive Antibodies (PRA %) and factors shown to be associated with poor platelet responses (spleen size, disseminated intravascular coagulation (DIC), bleeding, selected medications, history of hematopoietic stem cell transplant (HSCT) and/or graft versus host disease (GVHD), ABO compatibility, and product age). Platelet corrected count increments (CCI) were calculated for each transfusion. Non-HLA factors potentially contributing to CCIs at 0-2 and 18-24 hours post-transfusion were compared among HLA-compatible (either 4/4 HLA matched without HLA antigen mismatches, or with permissive mismatches (defined as cumulative a mean fluorescent intensity (MFI) &amp;lt;10,000 on the Luminex donor specific HLA antibody testing platform)) and HLA incompatible transfusions (cumulative MFI &amp;gt;10,000 or random donor apheresis products). Results: Of the 420 patients screened, 75 had sufficient records for inclusion. These subjects received 2729 platelet transfusions, an average of 36 transfusions per patient over 5.2 (± 4.1) months. Post transfusion platelet counts were available for 1528 transfusions. All platelet products were leukoreduced, irradiated, single donor apheresis products. Patients were predominantly Caucasian (70.7%; n=53/75), female (82.7%; n=62/75), aged 57 (±14.9) years. The primary diagnosis was Acute myelogenous leukemia or myeloproliferative disorder in most cases (88%; n=66/75). 58.7% (n=44/75) of patients were HSCT recipients (3 auto-; 41 allo-HSCT). Average PRA among patients was 72.4%±22.2%. 25 patients had splenomegaly. Among HLA-compatible transfusions, average CCIs at 0-2 and 18-24 hours were 17,088 and 6,666. In HLA-mismatched/random donor transfusions, average CCIs at 0-2 and 18-24 hours were 11,489 and 2,786; HLA compatible products increased CCIs by 5,599 and 3880 at 0-2 and 18-24 hours. In both groups splenomegaly had the most consistent association with poor CCI at both time intervals (Figures A and B). Conclusions: In this cohort of individuals with HLA-alloimmunization mediated PTR, the administration of HLA-compatible products offset the impact of other detrimental factors generating adequate CCIs at 0-2 and 18-24 hours. Among patients with splenomegaly, CCIs were lower despite HLA compatible product administration. In the same individuals, HLA-incompatible/random donor products negatively impacted CCIs overall and the negative effect of other concomitant non-immune/product-related factors was additive.Our data highlights the need to account for non-HLA related conditions while evaluating CCI response following each HLA-selected product transfusion, and to further explore any interactions among such factors. Next steps include conducting a multivariate analysis and developing a predictive model for platelet transfusion response in HLA-alloimmunized recipients who have concomitant non-immune or product related risk factors.

Alloantibody Levels, Immunoglobulin Degradation Products, and Platelet Transfusion Response over Successful Desensitization of Severe Alloimmune Platelet Refractoriness with a Novel IgG-Targeted Enzyme Therapeutic

INTRODUCTION Alloimmune platelet refractoriness (APR), an insufficient response to platelet transfusion due to anti-HLA alloantibodies, affects ~25% of acute myeloid leukemia (AML) patients. In APR, HLA- or crossmatch-compatible platelet units may not be identifiable, precluding transfusion and increasing hemorrhage risk. Single antigen bead testing (SAB) semi-quantitates antibody levels against cognate HLA antigens in units of mean fluorescence intensity (MFI). MFI &amp;gt;3,000 suggests an incompatible platelet antigen for transfusion. Imlifidase, an IgG-specific cysteine protease, cleaves IgG first into single-cleaved IgG (scIgG) with limited Fc-mediated function, then into inactive F(ab') fragments 1. We previously reported successful desensitization and provision of permissive platelet transfusions in an APR patient following desensitization treatment with imlifidase. Here we report pre- and post-desensitization alloantibody (PDAb) levels in correlation with IgG degradation products and response to single donor platelet transfusion. CASE As described previously 2, a 43-year-old highly sensitized (calculated PRA [cPRA] 99.9%) woman with AML and history of life-threatening thrombocytopenic hemorrhage secondary to APR presented for matched-unrelated donor stem cell transplantation. Nationwide, few compatible platelet units were identified to support her through the anticipated platelet nadir. Following conventional desensitization, cPRA did not change significantly. Following imlifidase-desensitization [0.25 mg/kg IV (D-1 and D1)], cPRA decreased significantly. 7 single-donor, antigen-avoidance platelet units produced corrected count increments (CCI) [median (interquartile range) of 6,000 (500-7500)]. The patient experienced no hemorrhage and was discharged stable, post-platelet engraftment on D+19. METHODS With IRB approval, patient data and samples (D-16; D-1 post-conventional desensitization with rituximab and therapeutic plasma exchange; D0 post-imlifidase dose 1; D2 post-imlifidase dose 2; and D7, D14 and D29 follow-up samples) were collected. Serial dilutions of patient D-1 serum were tested with SAB (LABScreen single antigen, One Lambda/ThermoFisher, West Hills, California). SDS-PAGE (gradient gel, non-reduced conditions), Western Blot (antiF(ab') detection), and SAB were performed and acceptable antigens (to molecular specificity, targeted by MFI ≤3,000) were compared over the clinical course. Summative MFIs targeting transfused single donor platelet units were compared with 1-hour CCI. Wilcoxon matched-pairs signed rank for matched, nonparametric values and Chi-squared or Fisher's exact for categorical variables were used. P &amp;lt;0.05 was significant. RESULTS/DISCUSSION The D-1 sample (post-conventional desensitization, pre-imlifidase) showed exquisite HLA sensitization. The highest Class A and B antibodies demonstrated an effective MFI of &amp;gt;4,000,000, each (Fig. A). PDAb and the number of unacceptable antigens decreased significantly in D0 (post-imlifidase) vs. D-1 (pre-imlifidase) samples; Intact IgG and scIgG were eliminated from the D0 and D2 samples (Fig. B). Of 7 single donor platelet transfusions, the 5 producing adequate response were each targeted by a summative MFI ≤4,000 (median 4,000 MFI, range 300-4,000). The 2 units producing inadequate CCI response were targeted by summative MFI &amp;gt;4,000 (5,050, 4,900-5,200), suggesting a threshold summative MFI precluding adequate response. CONCLUSIONS Here we show that the patient's pre-desensitization alloantibody levels significantly exceeded the analytical range of the SAB; PDAb levels declined significantly from baseline, correlating with lack of intact IgG and scIgG following imlifidase; and permissive transfusions (CCI &amp;gt;5,000) were seen to platelets targeted by ≤4,000 summative MFI. These results suggest imlifidase is capable of effective desensitization despite profound baseline sensitization, with rapid cleavage of intact IgG to F(ab'), resulting in the temporary reduction of unacceptable antigens. Larger scale investigation of imlifidase in desensitization of APR patients requiring significant transfusion over a limited period of time, along with investigation into transfusion strategies in desensitized APR, are warranted. REFERENCES Am J Transpl. 2022;22(3):691-697.Blood. 2022;140 (Suppl. 1):8562-3. .

Identification of Anti-HLA-C Autoantibody As Risk Factor for Primary Platelet Transfusion Refractoriness in Patients with Hematologic Disorders

Platelet transfusion is an important supporting treatment for hematologic disorders, especially in bone marrow failure disease and post-chemotherapy myelosuppression. However, in patients experienced multiple transfusions, platelet transfusion refractoriness (PTR) occasionally happened. Up to date, many factors had been explored contribute to the PTR, including infections, splenomegaly, antibodies against human leukocyte antigen class I (HLA-I) and antibodies against human platelet antigens (HPA). Based on our clinical practice, we also discovered that many cases had experienced primary PTR (who have been experienced PTR since the first platelet transfusion). Those patients suffered from severe thrombocytopenia can only be effectively corrected by cross-matching platelet transfusion. To our knowledge, anti-HLA-I-A and B antibodies had been reported to be in reference to immune-mediated PTR, while there are no conclusions about primary PTR. Herein, we identified anti-HLA-C autoantibodies was an independent risk factor for the primary PTR in patients with hematologic disorders, even refractoriness to cross-matching platelet transfusion or HLA-selected platelet transfusion. We retrospectively reviewed the patients that had HLA high resolution genotyping test report (potential for hematopoietic stem cell transplantation), and along with a donor-specific HLA antibodies (DSA) test or PRA testing potential for cross-matching platelet transfusion in our department between January 2019 and March 2023. 114 patients were enrolled, with a median age of 40 (14-80) years old, and the composition of disorders were aplastic anemia (65.8%), leukemia (21.9%), myelodysplastic syndrome (8.8%) and other (3.5%) (Fig A). Post-transfusion platelet efficacy was evaluated by the calculation of corrected count increment (CCI). The overall transfusion effective rate was 69.23% in this cohort, while 18.8% failed response from the first transfusion. Logistic regression analysis showed that only anti-HLA-I antibody contribute to the ineffectiveness of first and overall platelet transfusion (Fig B-E). In patients with positive anti-HLA-I antibodies, there were 35, 48 and 32 patients positive for anti-HLA-A, B and C antibodies, respectively (Fig A). Meanwhile, we surprisingly found that there were also 6 patients have anti-HLA-I autoantibody, including 6 on HLA-C and 1 have both HLA-A and C. To distinguish and gain a better understanding of the value of anti-HLA autoantibody in both TR and PTR, we further analyzed each locus of HLA-I and found that either anti-HLA-A, HLA-B or HLA-C antibody contribute to the ineffective to the overall and first platelet transfusion (Fig F-G), while logistic regression analysis revealed that only anti-HLA-C antibody was the independent risk factor (Fig H-K). We performed a logistic regression analysis with factors of anti-HLA-A, B antibody and anti-HLA-C autoantibody, and results showed that the association between positive anti-HLA-C autoantibody and the occurrence of PTR was significant ( P=0.008) (Fig J-M), while a difference approached the significance was also observed in overall platelet transfusion analysis ( P=0.054) (Fig N-O). In detail, we found that the effective overall platelet transfusion in the 6 patients who had anti-HLA-C autoantibodies was 20% (18 out of 90 transfusion), while for patients only have anti-HLA-C non-autoantibodies, it was 59.76% (47 out of 246 transfusion), a significant difference was observed ( P&amp;lt;0.001) (Fig P). For 3 patients with positive anti-HLA-C autoantibodies, all experience ineffective cross-matching platelet transfusion; while for the patients whom without anti-HLA-C autoantibodies, 21 patients experience cross-matching platelet transfusion and 17 of them response quite well, whit a significantly differences ( P=0.017) (Fig Q). In summary, our study demonstrated that positive anti-HLA-C autoantibody had a significant association with the occurrence of primary and overall PTR. The effects of cross-matching platelet transfusions in these patients are also unsatisfactory. To reduce the occurrence of PTR, our results suggested that it is necessary to anticipate the occurrence of PTR in patients with anti-HLA-C autoantibody positivity. Meanwhile, mechanisms should be explored and ways should be sought to lower the levels of such autoantibodies.

Efficacy and safety of platelet additive solution-E stored platelet concentrates.

In 2018, platelet (PLT) additive solution-E (PAS-E) was introduced. The implementation of PAS-E was expected to diminish the number of allergic reactions in recipients following a PLT transfusion. Here, we evaluated the efficacy and safety of transfusions with PLTs stored in PAS-E. After implementation of PAS-E, data were collected from 2 cohorts of patients with hematological disorders as well as oncology patients, receiving PLTs in PAS-E. A similar patient group in a recent RCT, receiving PLTs in plasma, was used as a historical control group for both cohorts. Endpoints were corrected count increments (CCIs), bleeding scores (only reported in cohort 1), and the incidence of adverse reactions. In cohort 1, the mean 1-h CCI was 14.3 ± 6.9, and the 24-h CCI was 8.7 ± 5.6. In cohort 2, the 1-h CCI was 11.6 ± 7.8 and the 24-h CCI was 7.0 ± 6.1. In the control group, the 1-h CCI was 15.4 ± 5.5 and 24-h CCI 8.7 ± 4.8. Bleeding complications of WHO grade ≥2 occurred in 40% of patients in cohort 1 compared to 44% in plasma PCs. The incidence of adverse reactions was 1.2% in the two PAS-E cohorts, compared to 3.0% in plasma PCs. National hemovigilance data showed a significant reduction in allergic reactions with PAS-E PC transfusions as compared to plasma PCs with an odds ratio of 0.46 (CI 95% 0.37-0.58). The CCIs of PLTs in PAS-E were decreased compared to plasma PCs, but clinically acceptable. Allergic transfusion reactions were decreased in PAS-E PCs compared to plasma PCs.

Factors Influencing Corrected Count Increment After Platelet Transfusion in Thrombocytopenic Patients.

Background Platelet transfusion is a life-saving procedure for thrombocytopenic patients. Platelet transfusions can be either prophylactic or therapeutic. Prophylactic platelet transfusion reduces the risk of bleeding before any specific procedure, whereas therapeutic platelet transfusion helps to control active bleeding. Evaluation of the response to platelet transfusion by calculating the corrected count increment (CCI) is important to determine the success of platelet transfusion and to plan subsequent patient management. Methods We conducted a prospective observational study in patients who received at least one unit of platelet concentrate (random donor platelet (RDP) or single donor platelet (SDP)) admitted under or seen by General Medicine. Patients over 60 years, multiparous females, and chemotherapy patients were excluded. The patient's pre-transfusion and post-transfusion platelet counts at one hour and 24 hours were taken, and CCI was calculated. Results We studied 60 patients during the study period, out of which 35 were males (58.33%) and 25 were females (41.67%). The mean age was 36.2 years, and the age range was from 15 to 60 years. The majority of patients were O-Rh positive (41.67%), followed by B-Rh positive (40%), A-Rh positive (11.67%), and least by AB-Rh positive (5%) and only one patient with O-Rh negative (1.67%). The logistic regression analysis showed that sepsis (p=0.025), splenomegaly (p=0.004), COVID-19 (p=0.016), dengue (p=0.028), systemic lupus erythematosus (SLE) (p=0.045), immune thrombocytopenic purpura (ITP) (p=0.003) and fever (p=0.007) significantly contributed to unsuccessful CCI. However, acute leukemia (p=0.238), active bleeding (p=0.147), disseminated intravascular coagulopathy (DIC) (p=0.952), aplastic anemia (AA) (p=0.114), and sickle cell disease (SCD) (p=0.739) did not show any statistical significance. Conclusion Unsuccessful CCI at 24 hours is attributed to non-immunological clinical factors like sepsis, splenomegaly, COVID-19, and fever, whereas immunological clinical factors like SLE, dengue, and ITP resulted in unsuccessful CCI at one hour, as evident by this study.

Prophylactic platelet transfusion response in critically ill patients: a prospective multicentre observational study

BackgroundResponse to prophylactic platelet transfusion is suspected to be inconsistent in critically ill patients questioning how to optimize transfusion practices. This study aimed to describe prophylactic platelet transfusion response, to identify factors associated with a suboptimal response, to analyse the correlation between corrected count increment and platelet count increment and to determine the association between poor platelet transfusion response and clinical outcomes.MethodsThis prospective multicentre observational study recruited patients who received at least one prophylactic platelet transfusion in one of the nine participating intensive care units for a period up to 16 months. Poor platelet transfusion response was defined as a corrected count increment (CCI) that adjusts for platelet dose and body surface area, less than 7 at 18–24 h after platelet transfusion. Factors associated with poor platelet transfusion response were assessed in a mixed-effect model. Sensitivity analyses were conducted in patients with and without haematology malignancy and chemotherapy.ResultsPoor platelet transfusion response occurred in 349 of the 472 (73.9%) prophylactic platelet transfusions and in 141/181 (77.9%) patients. The mixed-effect model identified haemoglobin at ICU admission (odds ratio (OR): 0.79 [95% confidence interval (CI) 0.7–0.89]) and body mass index (BMI) (OR: 0.93 [0.89–0.98]) being positively and independently associated with platelet transfusion response, while a haematological malignancy (OR 1.93 [1.09–3.43]), sepsis as primary ICU admission diagnosis (OR: 2.81 [1.57–5.03]), SOFA score (OR 1.10 [1.03; 1.17]) and maximum storage duration of platelet (OR: 1.24 [1.02–1.52]) were independently associated with a suboptimal platelet increment. Clinical outcomes did not differ between groups, nor the requirement for red blood cells. Poor platelet transfusion response was found in 93.5% of patients with haematology malignancy and chemotherapy.ConclusionsIn this study of critically ill patients, of whom more than half had bone marrow failure, almost three quarters of prophylactic platelet transfusions led to suboptimal platelet increment measured 18 to 24 h following platelet transfusion. Platelet storage duration was the only factor associated with poor platelet response that may be accessible to intervention.Trial registration in October 2017: ClinicalTrials.gov: NCT03325140.

A randomized cross-over study of cryopreserved platelets in prophylactic transfusions of thrombocytopenic patients.

The short shelf-life of liquid-stored platelets (LP) at 20-24°C poses shortage and wastage challenges. Cryopreserved platelets have significantly extended shelf-life, and were safe and efficacious for therapeutic transfusions of bleeding patients in the Afghanistan conflict and phase 2 randomized studies. Although hematology patients account for half of platelets demand, there is no randomized study on prophylactic cryopreserved platelet transfusions in them. We performed a phase 1b/2a randomized cross-over study comparing the safety and efficacy of cryopreserved buffy coat-derived pooled platelets (CP) to LP in the prophylactic transfusions of thrombocytopenic hematology patients. A total of 18 adults were randomly assigned 1:1 to CP and LP for their first thrombocytopenic period (TP) of up to 28-days. A total of 14 crossed over to the other platelet-arm for the second TP. Overall, 17 subjects received 51 CP and 15 received 52 LP. CP-arm had more treatment emergent adverse event (29.4% vs. 13.3% of subjects, 9.8% vs. 3.8% of transfusions) than LP-arm but all were mild. No thromboembolism was observed. Both arms had similar bleeding rates (23.5% vs. 26.7% of subjects) which were all mild. Subjects in CP-arm had lower average corrected count increments than LP-arm (mean [SD] 5.6 [4.20] vs. 22.6 [9.68] ×109 /L at 1-4 h, p < .001; 5.3 [4.84] vs. 18.2 [9.52] ×109 /L at 18-30 h, p < .001). All TEG parameters at 1-4 h and maximum amplitude (MA) at 18-30 h improved from baseline post-CP transfusion (p < .05) though improvements in K-time and MA were lower than LP (p < .05). During shortages, CP may supplement LP in prophylactic transfusions of thrombocytopenic patients.

Digital polymerase chain reaction to monitor platelet transfusions in cardiac surgery patients.

Corrected count increment (CCI) measurements monitor the effectiveness of platelet transfusions in haemato-oncology, but they usually fail in patients undergoing cardiac surgery. We investigated whether polymerase chain reaction (PCR) of mitochondrial single-nucleotide polymorphisms (SNPs) is able to monitor the survival of transfused platelets in these patients. Leukocyte-free, platelet-rich plasma was prepared from patients' blood to measure platelet counts based on patient-/donor-specific SNPs by digital PCR after DNA extraction. Platelet counts in samples from patients with severe thrombocytopenia were analysed by both PCR and flow cytometry. Ten patients undergoing cardiac surgery with the use of heart lung machine and without overt bleeding received a single apheresis platelet concentrate because of either dual platelet inhibition during a non-elective intervention or a complex procedure. Blood samples were collected at nine defined intervals (0-120 h) post transfusion. The digital PCR of the seven SNPs reliably quantified levels ≥0.6 G/L platelets, in good agreement with flow cytometry and without interference by other SNPs or by platelet activation. A mean 24-h CCI of 11.8 (range: 5.6-19.8) and a mean 120-h area under the curve (AUC) of 1386 (915-1821) hxG/L were observed for the transfused platelets. The mean AUC of 14,103 (3415-27,305) hxG/L for the patients' endogenous platelets indicates that transfused platelets represented only 11% (5-25) of the total platelet counts during 120 h post transfusion. PCR of mitochondrial SNPs offers a tool to assess the survival of platelets from apheresis concentrates in cardiac surgery patients to facilitate the implementation of improved transfusion strategies.

Effect of Platelet Concentrates (PCs) Leucodepletion on the Activation and Efficacy of Platelet Transfusion

Platelet concentrates (PCs) are blood components transfused in thrombocytopenic patients, including patients with blood malignancies. PCs contain leukocytes, which can pose potential side effects and activate platelets, reducing the efficacy of platelet transfusion. The leucodepletion process can be carried out by filtration to reduce the leukocyte count. This study aims to determine the difference between the CD62P expression of nonleucodepleted and leucodepleted PCs and to determine the difference between the Corrected Count Increment (CCI) of patients transfused with nonleucodepleted and leucodepleted PCs. This analytic observational study with a cross-sectional design was carried out on PCs obtained from platelet-rich plasma (PRP-PC). PCs were transfused into 48 blood malignancy patients, Yogyakarta, consisting of two groups i.e the group transfused with nonleucodepleted PCs (24 patients) and the group transfused with leucodepleted PCs (24 patients). CD62P expression in PCs was measured by flow cytometry method, and the CCI of the patients was calculated based on the CCI formula. The difference between the median CD62P expression and CCI of the two groups was analyzed using the Mann- Whitney Test with a significance of p<0.05. The median CD62P expression of the nonleucodepleted and leucodepleted groups were 34.4% (16.8–94.4%) and 21.7% (6.2–34.0%), respectively. There was a statistically significant difference between the CD62P expression of the two groups (p = 0.00). The group transfused with nonleucodepleted, and leucodepleted PCs showed respective median CCI of 18.8 x 109/L (2.4–94.8 x 109/L) and 14.7 x 109/L (2.4–124.0 x 109/L). There was no statistically significant difference between the CCI of the two groups (p = 0.42). It can be concluded that the CD62P expression in the PCs of the leucodepleted group was significantly lower than those of the nonleucodepleted group and that there was no significant difference between the CCI of both groups.