Platelet alloimmunization after transfusion. A prospective study in 117 heart surgery patients

Frequency of Platelet Crossmatch Positivity and Predictive Value for Poor Platelet Increment Among Paediatric Oncohaematology Patients in India

Immune platelet destruction is a significant cause for platelet refractoriness. The platelet crossmatch-a solid phase red cell adherence assay utilizes donor platelets and patient serum to assess compatibility and appears to be a feasible option in resource constrained settings. This study was done to evaluate the frequency of platelet crossmatch positivity among Paediatric Oncohaematology patients and also to assess whether a positive crossmatch is predictive of unsuccessful platelet transfusions in this group of patients. Paediatric Oncohaematology patients who received platelet transfusions between March 2013 and September 2013 were included in the study. The pre-transfusion patient sample and a segment from the transfused donor unit were used for performing the platelet crossmatch. A blood sample was collected one hour after the transfusion to assess post-transfusion platelet count. Corrected count increment (CCI) was calculated using the standard formula. CCI ≤ 7500/µL/m²/10¹¹ was considered evidence of an unsuccessful transfusion. Seventy-three platelet crossmatches were performed for 69 patients, of which 30 patient samples (41%) showed crossmatch positivity. 25 (89.2%) of 28 unsuccessful transfusions showed crossmatch positivity, and 40 (88.9%) of 45 successful transfusions showed negative crossmatches (p = 0.03). Crossmatch positivity among transfusion dependent Paediatric Oncohaematology patients was as high as 42%, when ABO matched platelet units were allocated without further testing. Our results indicate that this test may be a reliable tool to select compatible platelet units and an effective intervention in the management of patients at risk of immune platelet refractoriness.

Anti-HLA Class II Antibodies Correlate with C-Reactive Protein Levels in Patients with Rheumatoid Arthritis Associated with Interstitial Lung Disease

The pathogenesis of Rheumatoid Arthritis (RA) is not fully understood, probably influenced by genetic and environmental factors. Interstitial Lung Disease (ILD) is an extra-articular manifestation of RA, which contributes significantly to morbidity and mortality. The identification of anti-HLA antibodies has been useful in the transplantation field; however, its contribution to autoimmune diseases as RA has not been fully studied. We aimed to determine the presence of anti-HLA antibodies in RA patients with and without ILD and its possible association with clinical and biochemical markers. One-hundred and forty-seven RA patients, of which 65 had ILD (RA-ILD group), were included. Sera samples for Anti-HLA Class II LABScreen panel-reactive antibodies (PRA) were analyzed. In both groups, women predominated, and lung function was worse in patients with ILD. The anti-CCP+ (UI/mL) was higher in the RA group in comparison to RA-ILD (p < 0.001). Expositional risk factors (tobacco smoking and biomass-burning smoke) were higher in RA-ILD patients. PRA+ was identified in ~25% RA-ILD patients, while ~29% in the RA group. The CRP levels have a positive correlation with the percentage of reactivity (%PRA, p = 0.02, r2 = 0.60) in the RA-ILD group. In conclusion, anti-HLA antibodies correlate with C-reactive protein levels in RA patients with ILD.

HPA antibodies in Algerian multitransfused patients: Prevalence and involvement in platelet refractoriness

BACKGROUND

Patients receiving cellular blood components may form HLA or HPA antibodies. The frequency and the specificity of HPA antibodies after a series of blood transfusions have never been reported in the Algerian population which is ethnically diverse and runs a higher risk of platelet alloimmunization due to high b allelic frequencies observed for the HPA systems.

METHODS

117 polytransfused patients were included in this study; the detection of HPA antibodies was performed by the Monoclonal Antibody-specific Immobilization of Platelet Antigens method (MAIPA). Post-transfusion platelet effectiveness was evaluated by the calculation of corrected count increment (CCI).

RESULTS

The antibodies against platelets were detected in 10.26% of the patients. In this study, the platelet systems concerned by the alloimmunizations were specifically HPA-1, -3 and -5 with particular predominance of HPA-1. Twenty two patients were refractory to platelet transfusion, as assessed by a CCI; in which 64% have factors associated with increased platelet consumption. Platelet Immunization was found in 14% of platelet refractoriness (PTR) cases. 03 Anti-platelet antibodies were directed against GPIb-IX (n = 1), anti-HPA-1b (n = 1) and anti HPA-5b (n = 1) associated with anti-HLA antibodies in two cases.

CONCLUSION

HLA and HPA alloimmunization is common among chronically transfused patients. PTR detection, identification of the underlying causes, and selection of the appropriate product for transfusion are fundamental to reduce the risk of major bleedings.

Cross-match-compatible platelets improve corrected count increments in patients who are refractory to randomly selected platelets

BACKGROUND

Cross-match-compatible platelets are used for the management of thrombocytopenic patients who are refractory to transfusions of randomly selected platelets. Data supporting the effectiveness of platelets that are compatible according to cross-matching with a modified antigen capture enzyme-linked immunosorbent assay (MAC-ELISA or MACE) are limited. This study aimed to determine the effectiveness of cross-match-compatible platelets in an unselected group of refractory patients.

MATERIALS AND METHODS

One hundred ABO compatible single donor platelet transfusions given to 31 refractory patients were studied. Patients were defined to be refractory if their 24-hour corrected count increment (CCI) was <5×10(9)/L following two consecutive platelet transfusions. Platelets were cross-matched by MACE and the CCI was determined to monitor the effectiveness of platelet transfusions.

RESULTS

The clinical sensitivity, specificity, positive predictive value and negative predictive value of the MACE-cross-matched platelets for post-transfusion CCI were 88%, 54.6%, 39.3% and 93.2%, respectively. The difference between adequate and inadequate post-transfusion 24-hour CCI for MACE cross-matched-compatible vs incompatible single donor platelet transfusions was statistically significant (p=0.000). The 24-hour CCI (mean±SD) was significantly higher for cross-match-compatible platelets (9,250±026.6) than for incompatible ones (6,757.94±2,656.5) (p<0.0001). Most of the incompatible cross-matches (73.2%) were due to anti-HLA antibodies, alone (55.3% of cases) or together with anti-platelet glycoprotein antibodies (17.9%).

DISCUSSION

The clinical sensitivity and negative predictive value of platelet cross-matching by MACE were high in this study and such tests may, therefore, be used to select compatible platelets for refractory patients. A high negative predictive value demonstrates the greater chance of an adequate response with cross-matched-compatible platelets.

Transfusion-induced bone marrow transplant rejection due to minor histocompatibility antigens

Traditionally, alloimmunization to transfused blood products has focused exclusively on recipient antibodies recognizing donor alloantigens present on the cell surface. Accordingly, the immunologic sequelae of alloimmunization have been antibody mediated effects (ie, hemolytic transfusion reactions, platelet refractoriness, anti-HLA and anti-HNA effects, etc). However, in addition to the above sequelae, there is also a correlation between the number of antecedent transfusions in humans and the rate of bone marrow transplant (BMT) rejection-under reduced intensity conditioning with HLA-matched or HLA-identical marrow. Bone marrow transplant of this nature is the only existing cure for a series of nonmalignant hematologic diseases (eg, sickle cell disease, thalassemias, etc); however, rejection remains a clinical problem. It has been hypothesized that transfusion induces subsequent BMT rejection through immunization. Studies in animal models have observed the same effect and have demonstrated that transfusion-induced BMT rejection can occur in response to alloimmunization. However, unlike traditional antibody responses, sensitization in this case results in cellular immune effects, involving populations such as T cell or natural killer cells. In this case, rejection occurs in the absence of alloantibodies and would not be detected by existing immune-hematologic methods. We review human and animal studies in light of the hypothesis that, for distinct clinical populations, enhanced rejection of BMT may be an unappreciated adverse consequence of transfusion, which current blood bank methodologies are unable to detect.

Recent developments and future directions of alloimmunization to transfused blood products

Monitoring and managing alloimmunization are among the primary functions of the clinical transfusion medicine laboratory. However, despite hundreds of different blood group antigens that vary from person to person, only a minority of transfusion recipients become alloimmunized. Currently, there are no tests that predict which patients will become alloimmunized. Moreover, there are no therapeutic interventions to prevent alloimmunization (outside of RhD immune globulin) besides phenotypic matching. Understanding the biologic factors that regulate alloimmunization may allow the generation of clinical tests with predictive capabilities and provide a rational basis for developing therapeutic interventions. This article summarizes recent advances in understanding alloimmunization, with a focus of identifying future directions in laboratory testing and management of transfusion. In addition to analyzing humoral alloimmunization, potential extensions of transfusion medicine to sequelae of cellular immunization are explored.

Modification of solid phase red cell adherence assay for the detection of platelet antibodies in patients with thrombocytopenia

Platelet refractoriness is caused by HLA antibodies and platelet-specific antibodies. Current methods used to detect antiplatelet antibodies have limitations. Solid phase red cell adherence (SPRCA) lacks sensitivity and requires a second assay using chloroquine-treated intact platelets to specify the response due to anti-HLA. We modified SPRCA by using 2 types of antihuman platelet antibodies with different specificities toward platelet lysate and tested samples from 361 patients (69 with unexplained thrombocytopenia and 292 with poor response to platelet transfusions not explicable by alloimmunization or the clinical situation) and 50 from healthy volunteers. Our method compared favorably with platelet suspension direct immunofluorescence. All samples from healthy volunteers were negative; of the samples from the patient population, 240 were positive (147 samples had only antiplatelet and 3 samples had only anti-HLA antibodies). This modified technique had a sensitivity of 98% and a specificity of 91%.

Incidence of transfusion-induced platelet-reactive antibodies evaluated by specific assays for the detection of human leucocyte antigen and human platelet antigen antibodies

BACKGROUND AND OBJECTIVES

The aim of this work was to study the incidence of transfusion-induced platelet-reactive antibodies in a selective patient population and evaluate different methodologies for platelet antibody screening (PAS).

MATERIALS AND METHODS

The patients were retrospectively selected and divided into three separate groups: haematological malignancies (Group 1: n = 33); cardiac and orthopaedic patients (Group 2: n = 31) and a control group (Group 3: n = 23) selected with the same diagnoses of Group 2. PRE- and POST-transfusion samples were tested for PAS by the following tests: PIFT (platelet immunofluorescence test), MAIPA (monoclonal antibody immobilization of platelet antigen), Flow PRA(R) and LCT (lymphocytotoxicity test).

RESULTS

There was not a 100% concordance among the methodologies used. PIFT, MAIPA and Flow PRA presented very similar results whereas that of LCT differed from the other methods. A high rate of positive results (32%) was found in the PRE samples followed by an increase of almost 50% after blood transfusion (POST samples: 42.5% of positivity), but there was a statistical difference (P < 0.05) between the PRE and POST transfusion sample only for the Flow PRA(R) technique tested on Group 2. Human leucocyte antigen (HLA) class I antibodies were present on 97.4% of POST positive samples, 5.4% presented anti-human platelet antigen (HPA)-1b antibodies and 8.1% presented a mix of pan-reactive antibodies against glycoprotein IIbIIIa, IaIIa and IbIX.

CONCLUSIONS

Blood transfusion did not increase the rate of alloimmunization in our haematological patients (Group 1); however, the patients were already admitted with a high rate of alloimmunization (12%). Group 2 patients are being immunized and the impact of this procedure remains to be studied as these patients may eventually undergo further hospitalization and receive more blood transfusion.

Immunological aspects of blood transfusions

Donor selection based on blood group phenotypes, and blood processing such as leukocyte-depletion, gamma-irradiation or washing to remove plasma, are approaches for therapeutic or preventive use to manage the immunological complications of transfusion. Indications for specific components are prescribed in guidelines provided by (inter)national Transfusion Societies. Although the use of guidelines and protocols is in line with modern medicine, these can create a state of tension with the political sense of values to improve the viral safety of blood products and with the commercial exploitation of pooled plasma-products.A century of blood transfusion therapy has facilitated cancer treatment and advanced surgical interventions. The transfusion product has improved progressively, although mostly in response to disasters such as wars and AIDS. Every blood transfusion interacts with the immune system of the recipient. There are, however, very few quantitative figures to estimate the consequences. This review is based on the available literature on the clinical consequences of transfusion induced immunization and modulation. To a large degree the clinical consequences of transfusion induced immune effects are still a mystery.A blood transfusion is a medical intervention, which in many cases remains experimental with respect to the benefit/risk ratio. Ideally, this uncertainty should be communicated to patients and every transfusion included in a study. Such studies preferentially should be randomized because the perceived need for transfusion is associated with clinical conditions with a worse prognosis than those that do not receive transfusion. This difference may mask the interpretation of the transfusion effect. Since the blood supply services in almost all Western countries have been reorganized and nationalized, or at least operate to national quality standards, the measurement of risk: benefit of transfusion, whether political or evidence-based, needs to be reconsidered. Differences in emphasis and responsibilities between transfusion providers and transfusion prescribers will drive the providers to political and liability criteria - ever safer products - that will increase hospital costs with undetermined clinical benefits.

Use of HLA- and HPA--matched platelets in alloimmunized patients

Refractoriness for platelet transfusion is mostly due to clinical factors but may also be caused by alloimmunization. Use of leukocyte-depleted blood cells for transfusions of patients with hematological diseases has reduced if not eliminated HLA-alloimmunization. HLA-antibodies reduce the survival time of incompatible platelets complicating seriously the platelet transfusion support in at least 5% of patients. If consecutive transfusions of HLA matched platelets also fail without identifiable clinical causes, HPA-alloimmunization may have occurred. Platelets from donors phenotyped for both HLA and HPA may produce good platelet count increments and allow optimal treatment of the basic disease despite broad spectrum alloimmunization. Additional cross-matching of phenotyped platelets with patient serum may be needed to circumvent platelet-specific antibodies of unknown specificity.