Crossmatch Research Articles

C3d-binding assay for the detection of complement activating HLA antibodies: A useful tool for allocation to highly sensitised recipients in the post-CDC era?

The CDC crossmatch test is being phased out in solid organ donor allocation, and standard luminex single antigen bead assays do not differentiate complement activating function of HLA antibodies. The current study investigated the LIFECODES C3d-binding assay to determine if it could accurately predict actual T and B cell CDC results in a cohort of highly sensitised patients. Nineteen serum samples from different highly sensitised solid organ patients were crossmatched against cells from 62 unique donors, with 174 total T and B cell crossmatches performed. The sera also underwent SAB assay using OLI and LC platforms, and C3d-binding assay. Complement activating ability of each unique HLA antibody specificity detected using SAB was assigned based on the actual CDC results, which was then used to determine the accuracy of the C3d-binding assay. The C3d-binding assay was found to be highly accurate, with sensitivity of 95%, specificity 89% and negative predictive value 97% for class I DSA and the T cell CDC crossmatch results. Furthermore, we found 100% accuracy for prediction of the complement activating function of HLA-C antibodies. Negative predictive value of above 90% was also found for HLA class II DSA. C3d-binding proved more accurate than virtual crossmatch alone to predict CDC results. This study confirms that the C3d-binding assay predicts actual CDC crossmatch results accurately. In particular, the high negative predictive value of the C3d-binding assay may be extremely useful to define HLA antibodies that do not activate complement in highly sensitised recipients.

A catalogue of high-mass X-ray binaries in the Galaxy: from the INTEGRAL to theGaiaera

Context.High-mass X-ray binaries (HMXBs) are a particular class of high-energy sources that require multi-wavelength observational efforts to be properly characterised. New identifications and the refinement of previous measurements are regularly published in the literature by independent teams of researchers and might, when they are collected in a catalogue, offer a tool for facilitating further studies of HMXBs.Aims.We update previous instances of HMXB catalogues in the Galaxy and provide the community easy access to the most complete set of observables on Galactic HMXBs. In addition to the fixed version that is available in Vizier, we also aim to host and maintain a dynamic version that can be updated upon request from users. Any modification will be logged in this version.Methods.Using previous HMXB catalogues supplemented by listings of hard X-ray sources detected in the past 20 yr, we produced a base set of HMXBs and candidates by means of identifier and sky coordinate cross matches. We queried in Simbad for unreferenced HMXBs. We searched for as many hard X-ray, soft X-ray, optical, and infrared counterparts to the HMXBs as we could in well-known catalogues and compiled their coordinates. Each HMXB was subjected to a meticulous search in the literature to find relevant measurements and the original reference.Results.We provide a catalogue of 152 HMXBs in the Galaxy with their best known coordinates, the spectral type of the companion star, systemic radial velocities, component masses, orbital period, eccentricity, and spin period when available. We also provide the coordinates and identifiers for each counterpart we found from hard X-rays to the near-infrared, including 111 counterparts from the recentGaiaDR3 catalogue.

Impact of Low-Level Donor-Specific Anti-HLA Antibody on Posttransplant Clinical Outcomes in Kidney Transplant Recipients.

The clinical significance of low-level donor-specific anti-HLA antibody (low-DSA) remains controversial. We investigated the impact of low-DSA on posttransplant clinical outcomes in kidney transplant (KT) recipients. We retrospectively reviewed 1,027 KT recipients, namely, 629 living donor KT (LDKT) recipients and 398 deceased donor KT (DDKT) recipients, in Seoul St. Mary's Hospital (Seoul, Korea) between 2010 and 2018. Low-DSA was defined as a positive anti-HLA-DSA result in the Luminex single antigen assay (LABScreen single antigen HLA class I - combi and class II - group 1 kits; One Lambda, Canoga Park, CA, USA) but a negative result in a crossmatch test. We compared the incidence of biopsy-proven allograft rejection (BPAR), changes in allograft function, allograft survival, patient survival, and posttransplant infections between subgroups according to pretransplant low-DSA. The incidence of overall BPAR and T cell-mediated rejection did not differ between the subgroups. However, antibody-mediated rejection (ABMR) developed more frequently in patients with low-DSA than in those without low-DSA in the total cohort and the LDKT and DDKT subgroups. In multivariate analysis, low-DSA was identified as a risk factor for ABMR development. Its impact was more pronounced in DDKT (odds ratio [OR]: 9.60, 95% confidence interval [CI]: 1.79-51.56) than in LDKT (OR: 3.76, 95% CI: 0.99-14.26) recipients. There were no significant differences in other outcomes according to pretransplant low-DSA. Pretransplant low-DSA has a significant impact on the development of ABMR, and more so in DDKT recipients than in LDKT recipients, but not on long-term outcomes.

Impact of pre-transplant donor specific antibodies detected by Luminex with negative microlymphocytotoxicity assay and flow crossmatch in live-related renal transplant recipients.

The Luminex assay, where beads are coated with a single HLA antigen, has been shown to detect HLA antibodies with more sensitivity and specificity as compared to microlymphocytotoxicity (CDC) assay and flow cross match (FCXM). We report the impact of low Mean Flourescence intensity (MFI) pre-transplant DSA by Luminex with negative CDC and FCXM on acute rejection, graft function, and survival. In this retrospective study between January 2015 to December 2021, 45 recipients had pre-transplant anti-HLA donor-specific antibodies (DSAs) detected by Luminex. Two control groups of 45 patients each matched for age and gender, first with non-DSA HLA antibodies and second with no antibodies by Luminex were selected to compare outcomes with DSA group. In the DSA group of 45, 22 (48.8%) had class I (MFI mean 4043±1909, range: 1096-7111), 20 (44.4%) class II (MFI mean 3601±2310, range: 1031-9259), and 3 (6.6%) both class I (MFI mean 4746±1922) and class II (MFI mean 3940±2312) antibodies. Acute rejection episodes were reported in 15.6%, DSA group, 17.8% in non-DSA, and 24.4% in no antibody group (p=.538). Death censored graft survival at 1 and 5 years was 98% and 93% in DSA group, 100% and 95% in non-DSA and 93% and 85% in the no antibody group (p=.254). Patients with low MFI DSA pre-transplant, with a negative CDC and FCXM under ATG induction, have similar graft outcomes at 1 and 5 years when compared to non-DSA and no antibody groups.

Desensitizing With Temporary Donor Splenic Transplant: Hope for the Sensitized Patients on Pancreas and Kidney -Pancreas Transplant Waitlist

Sensitized patients on a waitlist with donor specific antibodies (DSA) or positive flow cytometry cross match (FXM) to deceased donor organ have few pretransplant desensitization options due to increasing graft cold ischemia time. Herein, sensitized simultaneous kidney/pancreas recipients received temporary splenic transplant from the same donor under the hypothesis that spleen would function as a DSA graveyard and provide a safe immunologic window for transplant. We analyzed presplenic and postsplenic transplant FXM and DSA results of 8 sensitized patients who underwent simultaneous kidney and pancreas transplantation with temporary deceased donor spleen between November 2020 and January 2022. Pre-splenic transplant, 4 sensitized patients were both T-cell and B-cell FXM positive; one was only B-cell FXM positive and 3 were DSA positive/FXM negative. Post-splenic transplant, all were FXM negative. Pre-splenic transplant class I and class II DSA were detected in 3 patients, only class I DSA in 4 patients, and only class II DSA in 1 patient. Postsplenic transplant, class I DSA was eliminated in all patients. Class II DSA persisted in 3 patients; all showed a marked decrease in DSA mean fluorescence index. Class II DSA was eliminated in one patient. Donor spleen functions as a DSA graveyard and provides an immunologically safe window for kidney-pancreas transplantation.

Acute hemolytic transfusion reaction following ABO-mismatched platelet transfusion: Two case reports

Acute hemolytic transfusion reaction following ABO-incompatible platelet transfusion: two case reportsAn ideal platelet transfusion should provide ABO identical platelet concentrate, and cross match compatibility is not routinely performed in the standard practices. However, ABO non identical platelet transfusions are not uncommon with the limited resources and short shelf life of platelet concentrate. Though rare, acute hemolytic transfusion reaction (AHTR) may occur following minor ABO-incompatible platelet transfusion. Here, we report two cases of thrombocytopenic patients (one child and one adult) type as Group B RhD positive and received Group O RhD positive platelet transfusions. Both patients experienced an AHTR evidenced by a drop in hemoglobin level, spherocytosis and small agglutinations on the blood film, and positive direct Coombs test. They were treated symptomatically, recovered and discharged well post-event without any morbidity. No anti-B isohemagglutinins titer were done to confirm the high titer of the antibody in the platelet donors. Our cases highlighted the importance of ABO-compatible platelet transfusion, especially to children and those vigilant groups of patients.

Analysis of Irregular Blood Group Antibody Distribution and Blood Transfusion Efficacy in Patients with Malignant Tumor

To investigate the distribution of irregular blood group antibodies in patients with malignant tumors, and to analyze the relationship between it and efficacy of blood transfusion in patients. 5 600 patients with malignant tumors treated in Shanxi Bethune Hospital from January 2019 to December 2021 were selected as the research subjects. All patients received blood transfusion, and cross matching test was conducted before blood transfusion, irregular antibody results of patients were tested; the irregular distribution of blood group antibodies was observed, and the relationship between it and efficacy of blood transfusion in patients was analyzed. Among 5 600 patients with malignant tumors, 96 cases were positive for irregular antibody, and the positive rate was 1.71%; the main blood group systems involved in the irregular antibody positive of 96 patients with malignant tumors were RH, MNSs and Duffy system, among which Rh blood group was the most common, and the proportion of anti-E was the highest; among the malignant tumor patients with positive blood group irregular antibody, the proportion of female was higher than that of male; the proportion of patients aged >60 years was the highest, followed by patients aged >40 and ≤50 years, and the proportion of patients aged 18-30 years was the lowest; the patients with positive blood group irregular antibody were mainly in blood system (including lymphoma), digestive system, reproductive and urinary system; the positive rate of irregular antibody of patients in the ineffective group was higher than that of patients in the effective group, the difference was statistically significant (P<0.05). Logistic regression analysis results showed that, irregular antibody positive was a risk factor for ineffective blood transfusion in patients with malignant tumor (OR>1, P<0.05). The irregular blood group antibody positive of patients with malignant tumor are mostly female, and the proportion of patients aged >60 is the highest, which is mainly distributed in malignant tumors of blood system, digestive system and urogenital system, and the positive blood group irregular antibody is related to the efficacy of blood transfusion in patients.

Facing adenocarcinoma of distal esophagus and esophago-gastric junction: A CROSS versus FLOT propensity score matching analysis of survival in a single-center institution

Facing adenocarcinoma of distal esophagus and esophago-gastric junction: A CROSS versus FLOT propensity score matching analysis of survival in a single-center institution

One shot learning approach for cross spectrum periocular verification.

The use of face mask during the COVID-19 pandemic has increased the popularity of the periocular biometrics in surveillance applications. Despite of the rapid advancements in this area, matching images over cross spectrum is still a challenging problem. Reason may be two-fold 1) variations in image illumination 2) small size of available data sets and/or class imbalance problem. This paper proposes Siamese architecture based convolutional neural networks which works on the concept of one-shot classification. In one shot classification, network requires a single training example from each class to train the complete model which may lead to reduce the need of large dataset as well as doesn't matter whether the dataset is imbalance. The proposed architectures comprise of identical subnetworks with shared weights whose performance is assessed on three publicly available databases namely IMP, UTIRIS and PolyU with four different loss functions namely Binary cross entropy loss, Hinge loss, contrastive loss and Triplet loss. In order to mitigate the inherent illumination variations of cross spectrum images CLAHE was used to preprocess images. Extensive experiments show that the proposed Siamese CNN model with triplet loss function outperforms the states of the art periocular verification methods for cross, mono and multi spectral periocular image matching.

Detecting Stepping-Stone Intrusion and Resisting Intruders’ Manipulation via Cross-Matching Network Traffic and Random Walk

Attackers can exploit compromised hosts to launch attacks over the Internet. This protects an intruder, placing them behind a long connection chain consisting of multiple compromised hosts. Such attacks are called stepping-stone intrusions. Many algorithms have been proposed to detect stepping-stone intrusions, but most detection algorithms are weak in resisting intruders’ session manipulation, such as chaff-perturbation. This paper proposes a novel detection algorithm: Packet Cross-Matching and RTT-based two-dimensional random walk. Theoretical proof shows network traffic cross matching can be effective in resisting attackers’ chaff attack. Our experimental results over the AWS cloud show that the proposed algorithm can resist attackers’ chaff attacks up to a chaff rate of 100%.

Donor-Specific Antibody Detection by Single-Antigen Bead Assay for Renal Transplantation: A 2-Year Experience from South India.

Recipient sensitization against donor human leukocyte antigens (HLA) plays a key role in transplant rejection, and this risk is best minimized by efficient pre transplant antibody detection. Determination of antibody specificity with the highest sensitivity and degree of resolution to the allelic antigen level is achieved by using single-antigen bead (SAB) assay. This study evaluated the correlation of Luminex cross match (LXM) with SAB assay for detection of donor-specific antibodies (DSA). A total of 2075 renal transplant patients were screened for the presence of DSA by LXM, complement-dependent cytotoxicity (CDC) cross match, and 125 patients for SAB from January 2018 to December 2019. There was a male preponderance among recipients (P < 0.0001), and the most affected age group was 21-40 years. HLA typing was done in 550/2075 by DNA PCR-reverse sequence-specific oligonucleotide probes (SSOP) method. HLA DSA by LXM was detected in 16.3% of recipients (338/2075). Majority 180/338 (53.2%) of the patients were class II DSA positive, (P < 0.0001). Among the class II DSA positive patients, 20/180 (11.1%) samples gave false-positive results by LXM. SAB for class I and class II HLA IgG antibodies was done in 125/338 renal transplant recipients, which included 20 recipients with false-positive class II Luminex DSA, to check whether the DSA detected were really donor specific or not. The results showed that although 20/125 patients had some antibodies detected in their serum, they were not against the donor HLA antigens, as per the HLA typing reports of the donors. When compared to SAB assay, LXM showed more discrepant results, particularly to class II DSA. In conclusion, LXM, if used in combination with SAB assay and HLA typing of donors if necessary for virtual cross match, will help in avoiding unnecessary exclusion of donors for renal transplant recipients and also for post transplant monitoring of recipients, especially in cadaveric donor transplants.

Type and Screen Method versus Antihuman Globulin Crossmatch in Pretransfusion Testing: A Cross-sectional Study

Introduction: Blood transfusion remains the primary modality of treatment for many serious and common diseases. According to the International Society of Blood Transfusion (ISBT), there are about 349 blood group antigens, out of which only about 25-28 antigens are known to cause acute or delayed type of haemolytic transfusion reactions which could be prevented by Pretransfusion Testing (PTT). Regulated pretransfusion tests include ABO blood grouping, Rh typing, antibody detection, antibody identification and compatibility testing. The purpose of compatibility tests is to demonstrate invitro red cell antigen-antibody reaction. The Antihuman Globulin (AHG) crossmatch testing can assure ABO compatibility between donor and patient blood as well as detect most clinically significant antibodies. Type and Screen (T&amp;S) is a procedure carried out as part of PTT in which the recipient’s blood sample is tested for ABO group, RhD T&amp;S for unexpected antibodies. Aim: To compare T&amp;S method of PTT with AHG crossmatch. Materials and Methods: This cross-sectional study was conducted in the department of Transfusion medicine at Government Royapettah Hospital, Chennai and The Tamil Nadu Dr. MGR Medical University, Chennai, Tamil Nadu, India from June 2012 to December 2013. T&amp;S was performed on 1,040 recipients’ (510 males and 530 females) samples. All these samples were subjected to AHG crossmatch with ABO group and RhD type matched donor samples to assess the compatibility between donor and recipient by using column agglutination technology. Statistical analysis was carried out using Statistical Package for the Social Sciences (SPSS) version 11.0. Results: The prevalence of unexpected antibodies in the recipient population was 1.06%. Among the 1,040 recipients’ blood samples, 11 samples were found to have unexpected antibodies. Out of these 11 samples, 10 showed exact antibodies and the remaining one sample with negative antibody screening was found to be incompatible with AHG crossmatch. The sensitivity and specificity of T&amp;S method in comparison to AHG crossmatch was 87.50% and 99.71%, respectively. Conclusion: The sensitivity and specificity of T&amp;S is as acceptable as AHG crossmatch. However, in view of one sample with false negative antibody screening in the study population, it is imperative to know the phenotyping of Red Blood Cells (RBC) antigens of the native population before getting away with AHG crossmatch.

Implant-Abutment Connections: A Structured Review.

The aim of the study was to carry out a structured review of studies that dealt with types of implant abutment connections, the concept of platform switching and its influence on hard and soft oral tissues. Electronic search was conducted over PubMed, Google Scholar, Medline, Embase to find articles dealing with Implant abutment connection and platform switching. We came across a total of 248 articles, which were filtered to a cumulative 19 articles after cross matching with predetermined inclusion and exclusion criteria. Most of the available literature gravitates in favor of an internal connection with the incorporation of platform switching to attain satisfactory hard and soft tissue outcomes.

Maximum surgical blood order schedule in urology surgery

Aim: To improve patient blood management (PBM), a special system of collecting and testing blood units has been developed. It defines the maximum number of allogeneic red blood cell components necessary for certain surgical interventions. This system is referred to as "The Maximum Surgical Blood Order Schedule" (MSBOS). The aim of the study was to evaluate the rationality of red blood cell consumption during urological surgeries. Materials and Methods: During the course of one year, a retrospective study was conducted on 617 patients. The study included 185 women and 432 men, with a median age range of 60 years old (ranging from 45 to 75 years old). The consumption of red blood cell units was evaluated in relation to the primary indication and type of surgery, preoperative data on hemoglobin values, and coagulation tests. Results: The overall C:T ratio was 4.2, which corresponds to 24% of transfused units in relation to the number of cross-match tests performed. A statistically significant difference in the average related to the age was observed between the subjects in whom there was irrational (64.65±9.49 years) and those in whom there was a rational use of red blood cells. A statistically significant difference was also observed in the frequency of different primary diagnoses according to the International Diseases Classification) and in relation to the values of hemoglobin and prothrombin time (PT) between the group with rational and irrational use of red blood cells. Conclusion: The obtained data showed unreasonable use of RBC based on the C:T ratio and therefore the necessity of introducing of PBM system as well the necessity to revise the existing protocols for red blood cell demand according to indications and to improve patient preparation in order to minimize the use of allogeneic red blood cells.

Understanding and management of adverse transfusion reactions

Blood transfusion is an essential supportive treatment in modern medicine and is frequently used. Acute hemolytic transfusion reaction is prevented by conducting a cross-matching test; however, nonhemolytic transfusion reactions are difficult to predict. Furthermore, adverse transfusion reactions are not sufficiently recognized by healthcare workers because they rarely occur, except for urticaria and febrile reactions. Thus, further awareness of adverse reactions, particularly regarding transfusion-associated circulatory overload, is needed. Since the introduction of irradiated blood, no transfusion-associated graft-versus-host-disease (TA-GVHD) case has been reported for over 20 years. However, education on the risk of TA-GVHD is important in facilities where nonirradiated blood is supplied or in situations such as unavoidable in-house blood collection on remote islands. The incidence of transfusion-transmitted hepatitis was significantly decreased by the introduction of nucleic acid amplification tests. Recently, the Japanese Red Cross Society is focusing on the reduction of transfusion-associated bacterial infections, which are rare but serious complications. This review provides an updated overview of adverse transfusion reactions and their management measures. Understanding adverse transfusion reactions will enable healthcare workers to recognize symptoms and take prompt action.

Cross Matching to Transfusion Ratios: Comparison between Menoufia University Surgical Departments, Egypt. Surprising Results

Cross Matching to Transfusion Ratios: Comparison between Menoufia University Surgical Departments, Egypt. Surprising Results

Prevalence of Rhesus negative blood group in surgical patients in a tertiary hospital in Rivers State, Nigeria

Background: The Rhesus-D negative blood group is not as common in Africans when compared to Caucasians thus the need to optimize surgical patients prior to surgical procedures. Blood group “O” Rh-D negative blood is a universal donor hence its importance in emergency situations where there is no time to type and cross match blood.This is because surgical patients may need blood transfusion pre-operatively, intra-operatively or post-operatively. Aim: To determine the prevalence of rhesus negative blood group in surgical patients in the Rivers State University Teaching Hospital (RSUTH). Method: This was a one-year retrospective study of surgical patients (Surgery and Obstetrics/Gynaecology departments) of the RSUTH. The patients comprised of all the consecutive cases of the surgeries in these departments for the period under review. Ethical clearance was obtained from ethical committee of the Rivers State Hospital Management Board. Structured profoma was used to extract information from patients’ case notes and analyzed using SPSS version 25. Result: A total of 370 patients were attended to pre-operatively. There were 146 (39.5%) males and 224 (60.5%) females. The mean age was 31 years. The age range was 22 years to 56 years. One hundred and ninety four (52.4%) were obstetrics and gynaecological surgeries while 176 (47.6 %) were non-gynaecological surgeries. The commonest indication for surgery was caesarean representing 126 (34.1%) of the subject.The distribution of Rh-D positive blood and Rh-D negative blood were 337 (91.7%) and 33 (8.9%) respectively. The prevalence of Rh-D negative blood group was 33 (8.9%) with blood group O Rh-D negative as the commonest 15 (4.1%). Conclusion: Our showed the prevalence of Rh-D negative blood group in surgical patients at the Rivers State Teaching Hospital as 8.9%. Rhesus–D “O” negative blood group was the most common representing 4.1% of Rhesus D-negative blood group. This makes it important in emergency surgical practice as universal donor when there may be to time for typing and matching prior blood transfusion.

DNA Identification in Mass Casualty – Forensic Perspective

Fire related mass casualty incidents have always been difficult in terms of identification. Often the bodies recoveredare in such bad shape making the process near impossible to get them identified through secondary methodsof identification. Extremely charred bodies having remnant burnt soft tissue and bones are most difficult to getidentified. It is exactly where Primary method of identification i.e. DNA Analysis comes into play.One such incident occurred at a Sanitizer manufacturing factory where tragic massive fire broke out engulfinglives of seventeen adult humans. The victims were trapped because of ongoing fire making it inescapable. Onautopsy, necessary samples were preserved and sent for DNA Analysis to Forensic Science Laboratory. Bloodsamples of all claiming relatives were also sent to the laboratory for cross matching of the DNA. Identity of allvictims was thus ascertained, once again proving how DNA Analysis has been a scientific boon to the humans.

Blood Transfusion Practices at Al-Thawra Teaching Hospital, Sana'a-Yemen

Objectives: To evaluate the blood transfusion practices, the quality and quantity and the use rate of blood and blood components among patients at Al-Thawra Teaching Hospital. Methods: This a descriptive study that has been conducted for the purpose of studying the blood transfusions fate and practices for all crossmatched units in the blood bank at Al-Thawra hospital during one month period, from December 2003 – December 2004. Data were collected from blood bank and from different departments in the hospital. Results: 960 units were crossmatched during the period of the study. The study showed that crossmatched units for male patients (56%) were higher than for female (44%). The recipient male/female ratio was 1.27: 1. The mean age of recipients was 31.6 years ± 18.3 SD. The commonest type of blood was blood group O (48%). 87.5% of crossmatched blood was done for stored whole blood in spite of availability of other components. Medical indications represented the highest percentage (40%). 26% of all crossmatched blood units were returned to the bank. The majority of collected blood was by family donation system. It was obvious that there was over-ordering and irrational use of the blood from the high percentage of unused crossmatched blood and the use of stored whole blood. Conclusion: Blood transfusion is necessary for saving the life of the patient who is in need, but blood should be only given when necessary, to minimize its complications and to cut off extra cost for cross matching of unneeded blood. The collection of blood from voluntary non-remunerated blood donors from low- risk populations should be encouraged. Modernization of blood banks with automated separator of the blood components is mandatory.

Comparison of platelet antibody screen, crossmatching and HLA antibody testing in patients refractory to platelet transfusions

Patients undergoing recurrent platelet transfusions can become refractory to these transfusions. Platelet antibody screens (Immucor), platelet crossmatching assays (Immucor), and HLA antibody testing are commonly used to test these patients. The relative effectiveness of these tests has not been determined. A higher incidence of strongly positive screen results that did not predict crossmatch results was anecdotally noted. Therefore, the results of the platelet antibody screens and crossmatches were systematically compiled over a 12-year period from 2010 to 2021. Of note, the Immucor Capture-P Ready Screen (platelet antibody) had a recall in March 2013 after which the performance of the test appears to have changed. The positivity rate of the platelet antibody screen increased over the course of the study, and this was statistically significant when analyzing year as a continuous variable and when grouping years by four-year periods (2010–13,2014–17,2018–21). In contrast, platelet crossmatch reactivity decreased slightly throughout this period. During the 2018–21 period, HLA antibody testing was commonly performed and correlated well with the crossmatch testing but not with the screen. These results suggest that the drastic increase in positivity we observed in the platelet antibody screen over this period is due to increased analytic sensitivity (with possible reduced specificity) of the screen and not a change in our patient population. Based on these results, the platelet antibody screen has little clinical utility and directly performing platelet crossmatching or HLA antibody testing is recommended for patients suspected to be refractory to platelet transfusions due to alloimmune-mediated factors.