Identification of platelet refractoriness in oncohematologic patients

OBJECTIVES: To identify the occurrence and the causes of platelet refractoriness in oncohematologic patients. INTRODUCTION: Platelet refractoriness (unsatisfactory post-transfusion platelet increment) is a severe problem that impairs the treatment of oncohematologic patients and is not routinely investigated in most Brazilian services. METHODS: Forty-four episodes of platelet concentrate transfusion were evaluated in 16 patients according to the following parameters: corrected count increment, clinical conditions and detection of anti-platelet antibodies by the platelet immunofluorescence test (PIFT) and panel reactive antibodies against human leukocyte antigen class I (PRA-HLA). RESULTS: Of the 16 patients evaluated (median age: 53 years), nine (56 percent) were women, seven of them with a history of pregnancy. An unsatisfactory increment was observed in 43 percent of the transfusion events, being more frequent in transfusions of random platelet concentrates (54 percent). Platelet refractoriness was confirmed in three patients (19 percent), who presented immunologic and non-immunologic causes. Alloantibodies were identified in eight patients (50 percent) by the PIFT and in three (19 percent) by the PRA-HLA. Among alloimmunized patients, nine (64 percent) had a history of transfusion, and three as a result of pregnancy (43 percent). Of the former, two were refractory (29 percent). No significant differences were observed, probably as a result of the small sample size. CONCLUSION: The high rate of unsatisfactory platelet increment, refractoriness and alloimmunization observed support the need to set up protocols for the investigation of this complication in all chronically transfused patients, a fundamental requirement for the guarantee of adequate management.

Antiplatelet antibodies in cases of Glanzmann's thrombasthenia with and without a history of multiple platelet transfusion.

Antiplatelet antibodies are known to be present in a wide spectrum of patients, which include chronic Idiopathic Thrombocytopenic Purpura (ITP), infections, etc., including Glanzmann's thrombasthenia (GT) patients who receive multiple platelet transfusions. The presence of natural antibodies to platelet receptors is not studied in cases of GT. We studied the antiplatelet antibodies in 23 patients with GT, 15 of which had received multiple transfusions and eight that had not received transfusions, along with 50 cases of chronic ITP. The prevalence and specificity of platelet-bound antibodies were detected by inhibition assays using O-group platelets on flow cytometry. The mean antiplatelet antibodies in 15 patients of GT who had not received transfusions and eight patients with multiple transfusions was 8427 + 2131.88 and 9038 + 2856 antibodies/platelet, respectively, while in case of the 50 ITP patients studied, it was 22166 + 5616 antibodies/platelet (Normal Range 1500–3200 antibodies/platelet). We conclude that GT patients who have not received transfusions may develop antiplatelet antibodies to the missing/abnormal receptor. Whether this is due to a molecular mimicry or due to some other mechanism needs to be explored.

Avaliação de diferentes metodologias laboratoriais para detecção de aloanticorpos plaquetários. Determinação da prevalência e importância clínica destes aloanticorpos em pacientes transfundidos / Evaluation of different laboratorial methodologies for the detection of platelet alloantibodies. Prevalence determination and clinical importance of these alloantibodies in transfused patients

A aloimunização contra antígenos plaquetários é um dos grandes desafios no tratamento de pacientes refratários à transfusão de plaquetas. OBJETIVOS: avaliar o desempenho de metodologias mais utilizadas em laboratórios de referência internacional para a pesquisa de anticorpos plaquetários (PAP); verificar a prevalência destes anticorpos na nossa população; avaliar se as transfusões estão causando aloimunização, e se estes aloanticorpos apresentam importância clínica. MATERIAIS E MÉTODOS: foram testadas amostras PRÉ e PÓS transfusionais em três grupos de pacientes sendo grupo 1 com patologias onco-hematológicas, grupo 2 com patologias não tumorais e grupo 3 composto dos mesmos tipos de pacientes do grupo 2 mas que não receberam transfusão (grupo controle). Numa primeira fase foi realizado estudo retrospectivo com amostras de soro congeladas no período de 1996 a 2001. A segunda fase consistiu em estudo prospectivo com amostras coletadas dos pacientes durante sua internação, no período de 2004 a 2006. Quatro diferentes metodologias foram testadas: imunofluorescência indireta por citometria de fluxo (PIFT), imobilização de antígenos plaquetários utilizando anticorpos monoclonais (MAIPA), teste de microlinfocitotoxicidade (LCT) e uma nova metodologia, conhecida como FLOW PRA N. Na fase 1 foram analisados 87 pacientes, e na fase 2, 96 pacientes, separados nos três grupos respectivamente. Na segunda fase do estudo, foi realizado o incremento da contagem corrigida de plaquetas (ICCp) para todos os pacientes que receberam transfusão de plaquetás. Para esta avaliação um novo grupo de pacientes (n=40) foi adicionado ao estudo, devido ao pequeno número encontrado na segunda fase. RESULTADOS: -as metodologias testadas apresentaram diferenças nas freqüências dos anticorpos detectados, porém as inefodologias MAIPA, PIFT e FLOW ´PRAPOT.TM´ foram as mais concordantes entre si...

A case report of neonatal alloimmune thrombocytopenic purpura: the importance of correct diagnosis for future pregnancies

CONTEXTO: Púrpura trombocitopênica neonatal aloimune (PTNA) é uma doença neonatal caracterizada por aloimunização materna contra as plaquetas fetais, que apresentam antígenos herdados do pai. Podem ocorrer hemorragias cerebrais, levando à morte ou a anomalias neurológicas permanentes. RELATO DE CASO: Mulher saudável, de 30 anos, deu à luz, por parto cesariano na 36ª semana de gestação, seu primeiro filho. Com 10 horas de vida, o recém-nascido apresentou petéquias e contagem de 8 x 103 plaquetas/µl no sangue periférico; foi medicado com imunoglobulina e recebeu alta após 18 dias de internação, com 100 x 103 plaquetas/µl. A causa da trombocitopenia não foi elucidada na época. Um ano depois, a criança morreu de neuroblastoma. Como os pais desejavam outro filho, foram encaminhados para investigação da trombocitopenia. Genotipagem plaquetária e pesquisa de anticorpos antiplaquetários foram realizadas, mostrando total falta de concordância entre os sistemas HPA-1 do pai (HPA-1a1a) e da mãe (HPA-1b1b) e anticorpos anti-HPA-1a no soro da mãe. Concluímos que o primeiro bebê nasceu com PTNA. Por isso, na segunda gravidez, a mãe foi tratada com diversas infusões de imunoglobulina intravenosa. Foi realizado cuidadoso monitoramento por ultra-som, com resultados normais para mãe e feto durante a gravidez. O segundo bebê nasceu por cesárea às 39 semanas, apresentando 92 x 103 plaquetas/µl seis horas após o nascimento. As plaquetas do recém-nascido foram genotipadas como HPA-1a1b e o soro da mãe novamente mostrou anticorpos anti-HPA-1a. Não houve hemorragia. A terapia de infusão de imunoglobulina foi efetiva na prevenção da PTNA no segundo filho.

Fetomaternal alloimmune thrombocytopenia presenting as intracerebral bleeding in utero.

Feto-maternal alloimmune thrombocytopenia is a serious fetal disorder resulting from platelet antigen incompatibility between the mother and the fetus. Intracranial bleeding is the most serious complication of alloimmune thrombocytopenia and can result in severe disability and death in utero. The authors report a case of intracerebral hemorrhage in utero resulting from alloimmune thrombocytopenia.

Flowcytometric evaluation of antibodies against histocompatibility antigens and platelet-specific antigens in patients with hematological disorders following the transfusion of platelets concentrates

Blood transfusion may lead to the manifestation of anti-HLA and platelet-specific antibodies that may in turn bring about different problems like platelet refractoriness. It appears that the study of antibodies against HLA-Class I and platelet-specific antigens are useful for the selection and success of the appropriate treatment protocol. The aim of this study was to detect anti-HLA and anti-platelet-specific antibodies by flowcytometry in patients with hematologic disorders [including Acute Leukemia, Aplastic Anemia] and patients with ITP. In this descriptive study, anti-HLA and platelet-specific antibodies were detected by flowcytometric technique, using 62 sera drawn from patients with different hematological disorders who showed a poor response to platelet transfusion and 20 from patients with ITP. The results of anti-HLA antibodies were then compared by Panel Reactive Antibodies [PRA]. Our results showed 44 [53.7%] out of 82 patients had anti-HLA Class-I antibodies in their sera. The frequency of each antibody isotype was found to be as follows: IgM [51.2%], IgG [32.9%] and IgA [1.2%]. 36 [43.9%] out of 82 patients had platelet specific antibodies and the frequency of each antibody isotype was found to be as follows: IgM [40.2%], IgG [30.5%] and IgA [12.2%]. 27 [31.7%] out of 82 patients had both antibodies. No difference was found between the two groups in platelet specific antibodies. Despite significant correlation between flowcytometry and PRA methods, PRA can only detect antibodies which react with complement. With increase in the number of platelet transfusion, immunization to HLA antigens occures; moreover, immunization against platelet specific antigens may also occure during autoimmunity. The presence of these antibodies may be one of the reasons of poor response to platelet transfusion and platelet refractoriness in patients under study. Conducting similar studies with higher number of samples, platelet cross-match, and the use of HLA- matched platelets for these patients are recommended