Integrating HLA and HPA in Precision Transfusion: Insights from Platelet Transfusion Refractoriness Driven by Anti-CD36 Alloimmunization and Multifactorial Hemostatic Complications

Shin-YiTsai1✉Emailstsai22@jhu.edu

Kuan-HsiaoLin5

Sheng-MouHou6✉Emailshengmou@blood.org.tw

1Department of MedicineMacKay Medical UniversityNew Taipei CityTaiwan

2Institute of Biomedical SciencesMacKay Medical UniversityNew TaipeiTaiwan

3Department of Laboratory MedicineMacKay Memorial HospitalTaipei CityTaiwan

4Department of Health Policy and ManagementJohns Hopkins Bloomberg School of Public Health, Johns Hopkins UniversityBaltimoreMDUSA

Taipei Blood Center, Taiwan Blood Service Foundation

6Taiwan Blood Services Foundation

Shin-Yi Tsai^1234*, Kuan-Hsiao Lin⁵, Sheng-Mou Hou^6*

¹Department of Medicine, MacKay Medical University, New Taipei City, Taiwan

²Institute of Biomedical Sciences, MacKay Medical University, New Taipei, Taiwan

³Department of Laboratory Medicine, MacKay Memorial Hospital, Taipei City, Taiwan

⁴Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health,

Johns Hopkins University, Baltimore, MD, USA

⁵Taipei Blood Center, Taiwan Blood Service Foundation

⁶Taiwan Blood Services Foundation

* Equal corresponding authors: S.Y.T. and S.M.H.

#Corresponding author:

Shin-Yi Tsai

Email: stsai22@jhu.edu

Sheng-Mou Hou

Email: shengmou@blood.org.tw

Introduction

CD36 (glycoprotein IV) is a heavily N-glycosylated class-B scavenger receptor expressed on platelets, monocytes, endothelium, and erythroid lineage cells^1,2. Early Blood studies defined the Naka– (CD36-negative) phenotype³ and established type I vs type II deficiency (absent on platelets ± monocytes)⁴, providing the immunohematologic framework for today’s diagnostics⁵. Its polymorphic expression on red cells and null variants, now recognized by The International Society of Blood Transfusion (ISBT), support designation of CD36 as a blood group system with clear clinical relevance ^6,7. Anti-CD36 is an important, often under-recognized cause of fetal–neonatal alloimmune thrombocytopenia (FNAIT) ^8,9,10 and fetal anemia^6,11, with Blood demonstrating effective prenatal therapy in preclinical models and editorially highlighting integration into perinatal workflows. ¹² Mechanistically, platelet CD36 surface density correlates with prothrombotic signaling responses^12,13 (e.g., to oxidized low-density lipoprotein (oxLDL))^14,15, informing why deficiency or alloimmunization can materially alter hemostasis¹⁶. In transfusion practice, anti-CD36–mediated platelet transfusion refractoriness (PTR) ^17,18 which should be considered when Human Leukocyte Antigen and Human Platelet Antigen (HLA/HPA) matching fails¹⁸, particularly in high-prevalence populations⁵ and might contribute to post-transfusion purpura (PTP) ^19,20. Finally, flow cytometry remains first-line for phenotyping^5,21, while optimized Monoclonal Antibody-specific Immobilization of Platelet Antigens (MAIPA) capture clones (GZ-70/GZ-608) markedly improve anti-CD36 detection over legacy reagents, enabling more reliable case ascertainment and targeted donor selection²².

CD36 deficiency exhibits significant geographic variation, affecting 2–4% of Chinese^23,24, 3%-11% of Japanese³, 2.6% of Middle Eastern²⁵, and up to 3% of African^26,27 populations, but remains rare(< 0.4%) in Europeans, accounting for the infrequency of anti-CD36 alloimmunization in Western cohorts.

Recent advancements in high-throughput sandwich Enzyme-Linked Immunosorbent Assay (ELISA) have outperformed conventional methods for CD36 phenotyping, achieving intra- and inter-assay variation as low as 2.1–5.2%²³. Diagnosis remains challenging due to the disorder's rarity and the need for multiplexed approaches beyond standard antibody screens, particularly in patients with comorbidities that can mask or mimic clinical features. Precise diagnosis relies on comprehensive assays, including flow cytometry²⁸, MAIPA²⁹, Solid Phase Red Cell Adherence Assay (SPRCA), ELISA, and molecular genotyping, for distinguishing CD36-related platelet alloimmunization from other causes. Our clinical series underscores the importance of integrated diagnostics for accurate identification in complex hemostatic disorders and guides optimal transfusion management.

Accurate detection of antiplatelet antibodies is essential in managing Immune Thrombocytopenia (ITP), Fetal and neonatal alloimmune thrombocytopenia (FNAITP), and PTR. At MacKay Memorial Hospital, since 2019, parallel testing using SPRCA and PAKPLUS® ELISA has revealed a persistent “gray zone” of detection discrepancies ³⁰. Integrating CD36 antigen typing and anti-CD36 antibody screening has been pivotal for elucidating PTR mechanisms and highlights the need for standardized thresholds to improve diagnostic precision.

Patients and methods

We would report that patients, including cases 1³¹, 2-4³², 5, and 6^32,33, have CD36 deficiency and CD36-related refractoriness.

Case 1

A 78-year-old female patient with lung adenocarcinoma and previously documented CD36 deficiency was admitted with respiratory distress attributed to pneumonia. Initial management included empiric antibiotic therapy, notably teicoplanin (400 mg IV daily), administered from January 30 to February 7 and resumed on February 25. Piperacillin/tazobactam was concurrently administered from January 30 to February 6. Meropenem was initiated on February 4 and continued until the patient's death. Ceftriaxone was added to the antimicrobial regimen from February 18 to February 25.

Case 2

was a 32-year-old pregnant female. Case 3 was a 60-year-old male with metastatic small-cell carcinoma, Sjögren's syndrome, and an unexpected PTR. Case 4 was a 21-year-old female with acute leukemia, cellulitis, Disseminated Intravascular Coagulation (DIC), and PTR. Case 5 was an 87-year-old female with chronic lymphoma, recurrent infections, dementia, chronic heart failure, and atrial fibrillation. Case 6 was a 48-year-old male with severe cardiovascular disease, ischemic gangrene necessitating multiple amputations, acute respiratory failure, and repeated surgical interventions.

In addition, our retrospective 5.5-year analysis of 2,333 samples tested via SPRCA and ELISA under standardized protocols at MacKay Memorial Hospital from January 2019 to June 2025³⁰. Positive results from either method triggered clinical interpretation. Discrepancies were considered concordant (positive/negative) or discordant (ELISA-only/SPRCA-only).

Methods

Clinical Assessment

Patients were evaluated for CD36 alloimmune risk using transfusion history, pregnancy, platelet increment records, and relevant clinical data.

Platelet Antibody Screening and Specificity Confirmation

Primary detection of platelet alloantibodies, including anti-CD36, utilized SPRCA. Wells were coated with anti-thrombocyte antibody, followed by PRP from 12 random donors and patient serum; indicator red blood cells identified antibody binding. SPRCA was supported by MAIPA, lymphocytotoxicity test (LCT), or chloroquine-modified SPRCA when results were unclear.

Supplemental ELISA: PAKPLUS

The PAKPLUS ELISA (Immucor) assessed serum reactivity against key platelet glycoproteins (GPIIb/IIIa, GPIa/IIa, GPIb/IX, GPIV/CD36, HLA) using kit controls; results were based on optical density.

Flow cytometric assessment of CD36 expression

Fluorescence Activated Cell Sorting (FACS) quantified platelet CD36 after dual labeling of PRP with FITC–anti-CD36 and PerCP–anti-CD41a; 5,000 CD41a + events were analyzed. Monocyte CD36 levels were measured in lysed whole blood using FITC–anti-CD36 and PerCP–anti-CD14, with analysis of 2,000 CD14 + events.

Molecular typing: CD36 exon 5 sequencing

Genomic DNA was extracted from EDTA-anticoagulated blood (MagCorePlus automated platform) from two CD36-deficient samples. Exon 5 and flanking intronic regions of CD36 were amplified using exon-specific primers (Forward 5′-AGATCTAATGTTCACATATG-3′; Reverse 5′-GATTAATTACATGAGTTCTAG-3′). PCR cycling was 35 cycles of denaturation 95∘C for 30 s, annealing 50∘C for 60s, and extension 72∘C for 30 s, with final extension 72∘Cfor 10 min. Amplicons were Sanger sequenced on an Applied Biosystems 3730xl DNA Analyzer at an external core facility, and sequence interpretation followed standard bidirectional trace review with base-calling quality control.

Quality control and interpretation

All serologic assays incorporated kit-provided and in-house positive/negative controls; runs not meeting control acceptance criteria were repeated. Ambiguous serology was adjudicated by orthogonal testing (chloroquine-modified SPRCA, MAIPA, and LCT) and by correlating with cellular CD36 expression and CD36 exon 5 sequence, where available.

Results

Case 1: Clinical Presentation

A middle-aged female developed progressive, extensive ecchymoses and significant soft tissue swelling during hospitalization. Skin disruptions and persistent serous exudation were observed. On February 7, the patient experienced acute, massive hematochezia (> 800 mL), with a rapid decline in hemoglobin and platelet count. Despite prompt transfusion of packed red cells, fresh frozen plasma, and pooled platelets, severe anemia and thrombocytopenia were refractory to therapy. Urgent colonoscopy revealed a large colonic perforation and diffuse skin bruising involving multiple sites.

Laboratory Findings

Laboratory evaluation demonstrated marked thrombocytopenia and coagulopathy³⁴: prolonged prothrombin time (PT/INR), elevated total and direct bilirubin, D-dimer, and fibrin degradation products, with low fibrinogen (Fig. 1;2C) ³⁵. Haptoglobin (< 30 mg/dL) suggested acute hemolysis or massive consumptive bleeding (Fig. 2B). Renal and hepatic function were impaired (Fig. 1), consistent with multi-organ involvement. Peripheral smear confirmed severe thrombocytopenia without schistocytes; thus, classic thrombotic microangiopathy was excluded. Absence of heparin exposure ruled out Heparin-Induced Thrombocytopenia (HIT).

Diagnostic Assessment

Given her known CD36 deficiency and history of multiple transfusions, immunologic studies were performed. ELISA and flow cytometry identified anti-CD36 (anti-Nak^a) alloantibody. Platelets demonstrated absent CD36 antigen expression, and MAIPA screening corroborated CD36 deficiency. Platelet transfusion with CD36-negative units was undertaken, resulting in sustained platelet recovery by February 19. Flow cytometric fluorescence profiles confirmed the absence of detectable anti-CD36 antibodies in the patient's serum (Fig. 3A-C).

Clinical Course

The patient received extensive transfusions, including CD36-negative platelets, leading to transient but significant platelet count improvement. (Fig. 2B) and received multiple broad-spectrum antibiotics (Fig. 2A), hemodialysis, and plasma exchange (Fig. 1). Despite these interventions, hemorrhage remained refractory, and multi-organ failure progressed due to ongoing DIC. Cutaneous manifestations included bilateral axillary, thoracic, and limb ecchymoses, with ruptured bullae and macular lesions on the thigh, highlighting severe bleeding and widespread vascular injury.

Clinical manifestations of severe DIC in a critically ill patient. The images depict extensive, confluent ecchymoses and purpuric lesions involving multiple anatomical sites, including bilateral axillary regions, the lateral thoracic wall, and extending along the upper extremities. The right thigh showed ruptured bullae and extensive macular ecchymoses surrounding it. These severe dermatologic involvement and widespread capillary leakage illustrate the profound hemorrhagic and thrombotic complications characteristic of PTR and advanced DIC, highlighting the clinical severity and extensive vascular compromise that may arise in such cases.

As Case 2 was pregnant and diagnosed with NAITP. Maternal flow cytometry conclusively demonstrated complete CD36 deficiency on platelets and monocytes, confirming maternal Type I CD36 deficiency. The paternal CD36 phenotype was positive, establishing an antigenic incompatibility capable of provoking maternal alloimmunization. (Fig. 4A-F) Further serological testing using SPRCA assays detected maternal anti-CD36 antibodies, with specific IgG affinity restricted to CD36-positive platelets. Crossmatch serology validated these results, documenting maternal serum binding exclusively to CD36-positive platelets without cross-reactivity to CD36-negative platelets. Neonatal serum lacked independent antibody activity, confirming passive transfer of maternal antibodies.

The neonate presented at birth with severe thrombocytopenia with an initial 40 × 10³/µL platelet count, clinically manifesting as petechiae. The platelet counts spontaneously increased to 332 × 10³/µL within eight days, consistent with a recovery pattern typical of NAIT. Concurrently, progressive anemia was observed, with hemoglobin levels declining from 12.6 g/dL at birth to 9.1 g/dL by day 8; however, this anemia could not be directly attributed to anti-CD36 antibodies. Additionally, intermittent neonatal desaturation episodes occurred, likely secondary to perinatal stress or infection rather than antibody-mediated mechanisms.

Case 3

Anti-CD36 was identified with SPRCA support, and a biallelic CD36 mutation elucidated the molecular homozygosity (Fig. 5E) underlying type I CD36 deficiency and provided genetic confirmation for the immunophenotypic absence of CD36 on platelets and monocytes, as characterized by flow cytometry in Fig. 5A-D. He had severe anemia due to melena, severe thrombocytopenia (~ 13–15K/µL), developed anti-CD36 alloantibodies after transfusions, explaining persistent PTR, and his cardiac/metabolic findings showed elevated NT-proBNP, potential exacerbation of cardiometabolic stress, and hyponatremia. Also, he felt fatigue, chest pain, and exercise intolerance.

Case 4

Anti-CD36 was definitively detected by SPRCA and presented absent CD36 on platelets and monocytes assessed by flow cytometry (type I deficiency) (Fig. 6A-D), and biallelic CD36 mutations confirmed the CD36 deficiency (Fig. 6E). She likewise formed anti-CD36, rendering her profoundly thrombocytopenic (~ 15K/µL), transfusion-dependent, and refractory to platelet support. Her cardiac findings included cardiomegaly, elevated BNP, and acute heart failure.

Case 5

The 46-year-old male patient's clinical course was marked by severe platelet refractoriness with an initial platelet count of 27×10³/µL and post-surgery, followed by a significant rebound thrombocytosis up to 758×10³/µL, upon recovery, exacerbated by repeated surgical stress, ischemic conditions, and systemic inflammatory responses from extensive tissue necrosis. While such fluctuations are typically indicative of consumptive coagulopathy, DIC, and reactive thrombocytosis following major surgery, recent specialized testing provides critical clarification. Flow cytometry on the patient's platelets and monocytes revealed significantly reduced or absent CD36 expression, confirming CD36 antigen deficiency. (Fig. 7A-H) Moreover, serological analysis demonstrated the presence of specific anti-CD36 antibodies via MAIPA and SPRCA, confirming alloimmunization.

He exhibited marked NT-proBNP elevation (1710 pg/mL), consistent with acute heart failure. The patient's history of hypertension, ¹¹ mellitus with complications, stroke, and ARDS-induced pneumonia points to severe cardiovascular and metabolic stress.

Case 6

The 86-year-old patient presented with thrombocytopenia predominantly associated with her underlying lymphoma, chronic infections, and age-related conditions, complicating definitive interpretation of CD36 involvement. Despite significant cardiomegaly and metabolic symptoms, typical manifestations directly attributable to CD36 deficiency were not definitively identified, and no anti-CD36 antibodies were detected.

Our findings indicated overall positivity: 33.6% (785/2,333), with ELISA detecting 33.6% (785/2,333) and SPRCA 18.7% (436/2,333). Concordance: 15.3% (356/2,333) positive in both methods and 62.9% (1,468/2,333) negative. Discordance: 18.4% (429/2,333) ELISA-only vs. 3.4% (80/2,333) SPRCA-only positives.

Statistical analysis showed Cohen's Kappa of 0.45 and an overall agreement of 78.2%. Since there is no definitive gold standard for antiplatelet antibody detection, neither method was considered the reference. Instead, we examined method-specific concordance: of the 436 SPRCA-positive samples, 356 (81.7%) were also positive by ELISA, while 80 (18.3%) were ELISA-negative. Among the 1,897 SPRCA-negative samples, 1,468 (77.4%) were also negative by ELISA, and 429 (22.6%) were ELISA-positive. The Cohen's Kappa value of 0.45 reflects moderate agreement between methods, accounting for chance.

Discussion

1. Clinical relevance

The clinical vignette (Case 1) demonstrates the catastrophic convergence of three distinct yet synergistic pathophysiological processes: anti-CD36 alloimmunization, Drug-induced thrombocytopenia (DITP), and DIC³⁴. DITP³⁶, notably associated with medications such as antibiotics, further complicates clinical management. Teicoplanin-associated DITP typically manifests 5–7 days post-exposure, aligning precisely with the observed thrombocytopenic episode: the patient's clinical deterioration timeline. The sequential administration of multiple broad-spectrum antibiotics, including meropenem and ceftriaxone, reflected the escalating concern for multidrug-resistant infections and the management of sepsis. The pathogenesis involves teicoplanin-dependent antibodies that recognize epitopes on GPIIb/IIIa or GPIb/V/IX complexes, leading to antibody-mediated platelet destruction.³⁷ Studies demonstrate a 4.6% incidence of teicoplanin-induced thrombocytopenia in clinical populations, with a median time to first platelet count drop of 5 days and a maximum drop occurring within 8 days.

Immunological assessment, including CD36 antigen typing and anti-CD36 antibodies, clarified immune-mediated platelet transfusion refractoriness caused by massive transfusions of standard random donor platelets, based on the high immunogenicity of CD36 and its widespread expression on donor platelets, most likely arising prior to sensitization, leading to the presence of anti-CD36 alloantibodies, necessitating the use of CD36-negative platelet transfusions for transient clinical improvement. However, persistent and consumptive coagulopathy DIC substantially magnified the risk of likely PTP, massive hemorrhage from a "perfect storm" of etiologies and thrombocytopenia severity coinciding with alloimmune and consumptive processes and impeded the efficacy of supportive interventions, treating infection and correcting coagulation factors, and targeted immunotherapy (e.g., IVIG for CD36 isoimmune PTR; platelet washing³⁸, leukoreduction³⁹, plasma exchange attempted to remove antibodies^40–42).

Such a scenario underscores the importance of a systematic approach to severe thrombocytopenia: elucidating temporal drug exposures through enhancing clinician awareness of DITP and stopping the offending drug promptly^37,43 and preventing reexposure⁴⁴; screening for alloantibodies and establishing registries for CD36-deficient donors and evaluating for DIC to direct appropriate therapy. Further research into therapeutic interventions for PTR complicated by anti-CD36 alloimmunization and DITP is warranted to refine clinical guidelines and outcomes. Consider reserving a compatible unit should bleeding risk or procedures arise.

Case 2

This clinical scenario underscores the critical necessity of promptly identifying maternal CD36 deficiency and associated alloimmunization in neonates presenting with unexplained severe thrombocytopenia. Accurate serologic detection of anti-CD36 antibodies facilitates early intervention and appropriate clinical management, potentially averting significant neonatal morbidity. ¹¹ Furthermore, distinguishing NAIT from non-immune etiologies such as infections or perinatal complications is paramount for optimal therapeutic decision-making and prognosis.¹⁰ Therefore, heightened clinical awareness to implement the expert panel throughout the prenatal to postnatal period^45,46 and comprehensive serologic assessments are strongly recommended in cases suggestive of alloimmune thrombocytopenia, particularly involving CD36 deficiency.

Early recognition of this anti-CD36-mediated refractoriness thrombocytopenia allows precision and restrictive transfusion strategies⁴⁷, such as selecting CD36-negative donors to source CD36-negative platelet units⁴⁸ and enhancing clinical monitoring, prophylactic measures during pregnancy, the antenatal administration of IVIG^49,50 and/or steriod^50,51, and/or deg-mAb 32-106¹¹, thereby optimizing patient outcomes and improving transfusion safety and efficacy.

Cases 3

and 4 highlight the essential role of specialized diagnostics in managing rare platelet alloimmunization and how CD36 deficiency intersects with complex diseases and confounds transfusion and Cardiometabolic Care. Flow cytometry and sequencing confirmed CD36 deficiency, while SPRCA assays verified the causative anti-CD36 antibodies. Severe thrombocytopenia directly reflects the immunohematology impact of anti-CD36 antibodies formed due to CD36 deficiency, which complicates underlying diseases and can exacerbate heart failure through impaired myocardial fatty acid metabolism ^52,53, potentially increasing susceptibility to cardiac dysfunction under metabolic stress⁵⁴. Critically impacts patient management by complicating transfusion therapy, increasing the risk of PTR, and potentially intensifying cardiometabolic instability in severe underlying diseases.

Minimize Platelet Transfusion; Immunosuppression/Desensitization

In the Case 4 scenario, an AML patient with anti-CD36. The immune PTR in patients with hematologic malignancies varies widely, from 7% to 34%⁵⁵. To minimize prophylactic platelet transfusions and transfuse only for bleeding is the optimized blood management⁴⁷. Withholding platelets during chemo-induced aplasia, unless bleeding occurs, can help reduce ongoing destruction of incompatible platelets and limit further immune stimulation.⁴ Moreover, temporary suppression of anti-CD36 production can be attempted. Regimens have included rituximab (anti-CD20 B-cell depletion), bortezomib (plasma cell targeting), and plasmapheresis to remove antibodies. In one severe case, these measures only modestly lowered antibody levels (anti-CD36) mean fluorescence intensity fell but rebounded within days)⁴, underscoring that current desensitization is often inadequate. Aberrant CD36 overexpression on leukemic blasts has been correlated with inferior complete remission rates and early relapse, reflecting its involvement in chemoresistance pathways and treatment failure. Furthermore, high CD36 expression is independently associated with poorer overall survival and event-free survival⁵⁶, likely mediated through altered lipid uptake, metabolic reprogramming, and enhanced leukemic stem cell persistence.^56,57 Collectively, these findings position CD36 not only as a predictive indicator of therapeutic response but also as a potential therapeutic target to overcome drug resistance and improve long-term outcomes in AML patients ⁵⁸.

Alternate Hemostatic Support: If platelets are ineffective, adjuncts like antifibrinolytics or thrombopoietin-mimetics might be considered, though evidence is limited. Experimental therapies are also being explored; for instance, an "effector-silencing" anti-CD36 monoclonal antibody has been proposed to block the patient's antibodies and permit safe transfusion.

In the case 5 scenario, with severe PTR, undetected CD36 alloimmunization was the cause.¹⁷ Namely, despite multiple platelet transfusions, his post-transfusion counts stayed near zero until an anti-CD36 isoantibody was identified, which led to rapid clearance of transfused platelets. In known CD36-deficient patients undergoing surgery or therapy, it is crucial to minimize allogeneic transfusions to prevent triggering anti-CD36 alloimmunization.

The literature on CD36 deficiency indicates complex metabolic interactions. Experimental data suggest a protective metabolic effect in CD36 deficiency regarding diabetic cardiomyopathy and atherosclerosis⁵⁹. However, the patient's severe phenotype underscores the multifactorial nature of cardiovascular disease, particularly in chronic diabetic⁵⁴ and hypertensive contexts.⁴⁶

CD36 plays a critical role in platelet activation and lipid metabolism and has been proposed as a therapeutic target for reducing thrombotic risk in dyslipidemic individuals^47,59,60. Type I CD36 deficiency is associated with atherosclerosis⁶¹, altered glycolipid metabolism⁶², and cardiomyopathy⁶³. In CD36-deficient myocardium, reduced fatty acid uptake shifts energy metabolism toward glucose utilization, impacting myocardial remodeling and function. Clinically, type I CD36-deficient patients, especially those without prior anti-CD36 alloimmunization, require careful perioperative and transfusion management⁶⁴ due to potential metabolic and hemostatic alterations.⁶⁵

Beyond transfusion reactions, CD36 deficiency has far-reaching systemic implications that can affect cardiovascular health, neurological injury responses, and metabolic regulation, including attenuation of diabetic cardiomyopathy and less ischemia-reperfusion myocardial damage⁶². In platelet function studies, CD36 deficiency leads to slower thrombus formation^52,59,66 and CD36-null platelets are less responsive to thrombogenic stimuli like oxidized lipids, resulting in delayed clotting on thromboelastography³⁴. These findings imply that CD36 deficiency might protect against acute ischemic events such as myocardial infarction or stroke in specific contexts. Indeed, absence of CD36 improved outcomes in stroke models⁶⁷, with CD36-deficient animals showing smaller brain infarcts, better blood–brain barrier integrity, and superior functional recovery post-stroke⁶⁸.

These cases underscore the critical role of sophisticated platelet antibody detection methods in differentiating CD36-related pathology from thrombocytopenia caused by other chronic diseases. The presence of severe underlying conditions, particularly lymphoma and extensive surgical trauma, profoundly influences the clinical manifestations of CD36 deficiency. Accurate identification of anti-CD36 antibodies through MAIPA and SPRCA assays enables tailored management strategies, emphasizing the need for high diagnostic suspicion and specialized testing in complex clinical scenarios.

In contrast, as in Case 6 with lymphoma-related thrombocytopenia, a CD36-negative patient without alloantibodies can initially receive standard platelets without immediate clearance because no anti-CD36 is present to destroy them. However, her transfusion refractoriness likely stemmed from non-immune factors (e.g., splenomegaly or HLA antibodies) rather than CD36 alloantibodies. Such a patient was at high risk of developing anti-CD36 after any transfusion. This risk calls for proactive blood management, including the restrictive transfusion policy and early antibody screening.

In summary, CD36 deficiency confounds transfusion outcomes by introducing an oft-overlooked immune barrier. Unrecognized, it leads to refractory thrombocytopenia despite adequate platelet doses⁶⁹. Once identified, clinicians must tailor transfusion support (e.g., sourcing rare donors or employing immunosuppression) to circumvent this alloimmune destruction, and to provide leukoreduction lowered alloimmune platelet refractoriness from 14% to 4% in patients receiving chemotherapy for acute leukemia or stem cell transplantation ^39,56. The profound refractoriness seen with anti-CD36 (Case 5) versus the routine management of thrombocytopenia without such antibodies (Case 6) highlights the clinical impact of CD36 alloimmunization in hematology practice. Finally, the immune dysregulation and metabolic consequences of CD36 deficiency intersect significantly with cancer care. CD36 is a pattern-recognition scavenger receptor on monocytes, macrophages, and dendritic cells that binds danger signals (DAMPs) and pathogen components (PAMPs)⁷⁰. It facilitates phagocytosis of bacteria and cell debris and modulates cytokine production during infections. CD36 is presented in diverse cancer cells and immune cell subsets with pro- and anti-tumorigenic roles.⁷¹

In patients with hematologic malignancy, an intact innate immune response is critical since they are often neutropenic or lymphopenic from chemotherapy²⁴. So, the maximal function of macrophages and remaining immune cells is needed to fight infection. CD36 deficiency can impair innate immunity, for example, by reducing macrophage uptake of Gram-negative bacteria and dampening Toll-like receptor signaling for cytokine release. This could leave an immunocompromised cancer patient even more vulnerable to sepsis or fungal infections ^72,73.

2. Recommended Diagnostic Strategy

Clinical Interpretation of ELISA versus SPRCA: Agreement and Clinical Implications

Overview of Agreement Metrics

The comparative analysis of 2,333 samples assessed by ELISA and SPRCA revealed an overall concordance rate of 78.2%. Specifically, the positive percent agreement (PPA) stood at 81.7%, indicating that ELISA successfully identified approximately 82% (356 of 436) of samples determined to be positive by SPRCA. Conversely, the negative percent agreement (NPA) was 77.4%, showing ELISA accurately classified about 77% (1,468 of 1,897) of SPRCA-negative samples. Cohen's κ coefficient of approximately 0.45 underscores a moderate level of agreement after adjustment for chance, suggesting meaningful yet incomplete concordance between these diagnostic modalities.

The discordance patterns between ELISA and SPRCA were notable. ELISA detected an additional 18.4% of samples beyond SPRCA detection, whereas SPRCA uniquely identified 3.4% of samples, yielding an overall discordance rate of 21.8%. These findings underscore the non-interchangeable yet complementary diagnostic roles of the two assays. ELISA's higher detection rate may indicate the detection of low-affinity or non-pathogenic antibodies. In contrast, SPRCA's more restricted detection profile correlates with clinically significant antibodies, consistent with previous reports highlighting SPRCA's dependence on antigen density and reduced nonspecific binding; hence the moderate agreement (κ ≈ 0.45). Considering the limitations of some methods, adopting a tiered and sequential two-step diagnostic strategy is recommended.

GP-specific antibody assays best identify anti-Nak (a). Still, false negatives can result from monoclonal antibody interference that blocks human antibody binding.¹³ Conventional platforms, including Luminex bead assays and the MAIPA assay, often miss anti-CD36 due to epitope competition with capture antibodies (clone FA6-152). Employing ELISA for initial comprehensive screening is advocated owing to efficiency and scalability. Subsequently, all ELISA-positive samples should undergo confirmatory testing via SPRCA or alternative high-specificity assays, such as MAIPA²² or flow cytometry²⁴ is mandatory for clinical decision-making. Dual ELISA- and SPRCA-positive results strongly support pathogenicity, while discordant cases demand comprehensive clinical and laboratory correlation, including transfusion history and symptom analysis. This integrated approach increases reliability in anti-CD36 detection, informs management of thrombocytopenia, and is supported by emerging evidence. Namely, interpretation guidelines for clinical decision-making should be considered as follows. First, samples positive by both ELISA and SPRCA carry high clinical validity, strongly suggesting genuine positivity. Second, discordant findings (ELISA-positive/SPRCA-negative or ELISA-negative/SPRCA-positive) warrant further reflex testing or comprehensive clinical correlation, including a review of transfusion history, clinical symptoms, and additional laboratory investigations.

Overall strategies:

Adopting the proposed diagnostic algorithm significantly enhances patient safety by effectively identifying individuals at genuine immunologic risk, reducing the incidence of immune-mediated PTR.

The gold standard for treating anti-CD36 PTR is transfusion with platelets that lack the CD36 antigen³, thereby evading destruction by circulating alloantibodies⁷⁴. Establishing and maintaining registries of CD36-negative donors is a recurring theme in high-impact studies, as these rare individuals are critical for successful management. This approach optimizes laboratory resource allocation, minimizing unnecessary testing and enabling targeted interventions, especially among patients with discordant test results or those clinically suspected to be at elevated risk.

Acknowledgements

We sincerely acknowledge the medical teams, the Blood Bank of MacKay Memorial Hospital and Taipei Blood Center, Taiwan Blood Services Foundation for their dedicated support and expertise in transfusion medicine. Their unwavering commitment to rigorous standards in blood collection, testing, and specialized transfusion services was essential to the successful completion of this study. The staff’s collaboration and careful attention to both patient care and laboratory quality greatly enhanced the integrity of our research.

Declarations

Ethics approval and consent to participate

This study was approved by the Institutional Review Board of MacKay Memorial Hospital.

Consent for publication

The authors agree with the publication of this paper

Declaration

of originality

The authors confirm that this manuscript is original and independent from other submitted or published works.

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Yes