血小板特异性糖蛋白抗体在血小板输注无效患者中分布的研究

目的探讨血小板输注无效(PTR)患者的血小板特异性糖蛋白抗体的表达及PTR与血小板特异性抗原的相关性。方法采用ELISA方法检测27名临床上确诊为PTR患者的血小板特异性糖蛋白抗体,应用PCR-SSP的方法检测其HPA-1～17基因分型。结果 27名PTR患者的HPA基因频率为HPA-1a(0.900),1b(0.100);HPA-2a(0.926),2b(0.074);HPA-3a(0.648),3b(0.352);HPA-4a(0.981),4b(0.019);HPA-5a(0.940),5b(0.060);HPA-6a(0.815),6b(0.185);HPA-7a～14a、16a、17a(1.000),7～14、16、17b(0.000);HPA-15a(0.463),15b(0.537);PTR患者的HPA抗原分布与健康献血者的基因频率无统计学差异(P>0.05)。血小板抗体阳性的27名PTR患者中,血小板特异性糖蛋白GPⅡb/Ⅲa抗体阳性表达者占78%(21/27)、GPⅠa/Ⅱa抗体阳性占70%(19/27)。对3名PTR患者作血小板特异性抗原分析发现:患者产生的血小板特异性糖蛋白抗体与HPA基因型密切相关,以抗-HPA-3b、-5b为常见。结论多次输注血小板无效的患者,应选择与其HPA基因型一致的血小板供者,以提高血小板输注疗效,避免血液资源的浪费。     

血小板输注无效患者血小板同种抗体及血小板特异性糖蛋白抗体表达的研究

目的 探讨血小板输注无效与血小板同种抗原或血小板特异性抗原的相关性.方法 选择65例临床确诊血小板输注无效患者作为研究对象,应用酶联免疫吸附实验(ELISA)方法检测血清、血小板洗脱液中血小板特异性抗体;应用HLA抗体特异性检测试剂盒,对组合反应性抗体(PRA)阳性的患者进行HLA抗体特异性分析;用HPA分型试剂盒检测8个血小板同种抗原系统HPA-1、2、3、4、5、6、9、15;用HLA分型试剂盒对HLA-A/B抗原进行基因分型.结果 65例患者HLA-A/B抗原,HPA-1、2、4、5、6、9、15抗原的基因频率分布与健康献血员比较差异无统计学意义.HPA-3a、3b抗原频率分别为0.65、0.35,与健康献血员比较差异有统计学意义(P＜0.05).65例患者中HLA抗体单独阳性24例(36.9%),HLA抗体和血小板特异性糖蛋白抗体共同阳性14例(21.5%);HLA抗体和血小板洗脱液特异性糖蛋白抗体共同阳性6例(9.2%),血小板洗脱液特异性糖蛋白抗体阳性13例(20%),HLA抗体、血小板特异性糖蛋白抗体及血小板洗脱液特异性糖蛋白抗体共同阳性4例(6.2%);HLA-A/B特异性抗体中,HLA-A*9抗体占全部抗体的46.2%,HLA-B*40抗体占33.6%.血清血小板特异性抗体以GPⅡb/Ⅲa为主(26.2%),其次为GP Ⅰa/Ⅱa(21.5%),血小板洗脱液中,血小板特异性抗体以GPⅡb/Ⅲa和GP Ⅰb/Ⅸ为主(41.5%).对2例患者进行了遗传学调查,发现产生的血小板特异性糖蛋白抗体和HLA抗体与父母血小板抗原及HLA抗原不相合呈密切相关.结论 血小板输注无效患者中,HLA抗体占主要地位,其次为血小板特异性糖蛋白抗体.     

血小板谱抗原的建立及其在鉴定血小板特异性抗体中的应用

目的 建立血小板谱抗原,鉴定引起血小板输注无效和新生儿血小板减少性紫癜的血小板特异性抗体,为血小板血型研究和临床治疗提供依据。方法根据中国人群人类血小板同种抗原(HPA)-1-HPA-16等位基因频率分布资料,利用聚合酶链反应-序列特异引物(PCR-SSP)技术对O型血小板供者进行HPA-1-HPA-6、HPA-15分型,筛选合适的供者,组成血小板谱抗原。通过建立的血小板谱抗原,利用简易致敏红细胞血小板血清学技术(SEPSA)鉴定同种免疫反应产生的血小板抗体的特异性。结果从O型血小板供者中筛选出11名供者,建立了血小板特异性抗体鉴定谱抗原。其可鉴定HPA-1-HPA-6,HPA-15抗体的特异性。在所筛检1 120份样本中,有3例患者检出HPA抗体,其中HPA-4b(Penb)抗体1例,HPA-15a(Govb)抗体2例。结论通过血小板谱抗原鉴定血小板抗体的特异性,对提高临床输注血小板的安全性和有效性,以及预防新生儿血小板减少性紫癜有积极的意义.     

输血患者的血小板同种异型抗体

背景 输注血细胞成份的患者可能形成HLA抗体和血小板特异性同种异型抗体。研究设计和方法 收集252例输注血细胞成份的血液病和肿瘤患者的血清样本,研究血小板反应性抗体。血小板同种异型抗体的特异性用一组已定型的血小板来确定。结果 113例患者(252的44.8％)的血清检测血小板反应性抗体,108例患者(42.9％)的血清检测HLA抗体,20例患者(8％)的血清检测血小板特异性抗体。鉴定了以下血小板特异性抗体:抗-HPA-5b(n=10),抗-HPA-1b(n=4),抗-HPA-5a(n=2),抗-HPA-1a(n=1),抗-HPA-2b(n=1),抗-HPA     

改良抗原捕获ELISA在血小板抗体检测及配型中的应用

目的探讨改良抗原捕获ELISA(MACE)在血小板抗体检测及配型中的应用。方法采用MACE分别检测青岛地区医院送检48例血小板输注无效(PTR)患者血清中的血小板同种抗体和32例特发性血小板减少性紫癜(ITP)患者血浆中的血小板自身抗体,并为PTR患者进行血小板配型。结果PTR患者血小板同种抗体检出率为50%(24/48),其中同种HPA抗体阳性率为29.2%(14/48),同种HLA抗体阳性率为39.6%(19/48),抗-HLA占所有免疫性抗体的70.4%(19/24)。ITP患者血浆游离抗体检出率62.5%,其中抗体阳性者全部检出自身抗体,而且全部有抗自身HPA抗体。选择配合性血小板52个治疗量输注,输注后24小时CCI值为(11.35±2.78)×109/L,总有效率82.3%。结论MACE法可以常规应用于PTR患者的血小板抗体检测及配型;MACE法检测血浆中游离的血小板自身抗体可做为辅助诊断ITP的一种方法。     

HPA配型在免疫性血小板输注无效中的应用研究

目的探讨以HPA配型解决免疫性血小板输注无效的方案。方法 1)建立PCR-SSP方法检测HPA-1～5基因型检测方法,建立机采血小板供者库;2)采用微柱凝胶法和Capture-P法对32名血小板输血无效患者作血小板同种抗体筛查,并对2种方法比较;3)对血小板同种抗体筛查阳性患者采用已知HPA基因型的标准谱血小板作抗体鉴定并采取HPA基因型同型输注的原则寻找供者。结果 1)采用PCR-SSP方法成功检测出HPA-1～5基因型,并对1 000名血小板供者的HPA-1～5基因型定型;2)32例血小板输注无效病例中,微柱凝胶法检测血小板同种抗体阳性率为50%,Capture-P法血小板抗体阳性检出率为40%;3)32例血小板输血无效病例中2种方法同时血小板抗体阳性13例,其中2例鉴定为抗-HPA,分别为抗-HPA-5b(P=1/84)、抗-HPA-1a(P=1/55)。结论对抗-HPA引起的血小板输注无效患者采用HPA基因型相合的方法寻找供者是有效的。     

哈尔滨地区血小板输注无效患者的抗体鉴定与分析

目的探讨与分析哈尔滨地区免疫性血小板输注无效患者血小板抗体类型。方法对2017年11月-2018年6月的38例临床血小板输注无效的交叉配型阳性的患者,采用PAKPLUS试剂盒进行血小板特异性抗体鉴定,分析患者HLA抗体和HPA抗体分布情况。结果 36例患者出现抗体阳性,其中单一HLA-Ⅰ类抗体阳性5例(13.9%),单一HPA抗体阳性3例(8.3%),HLA-Ⅰ类抗体和HPA抗体均阳性28例(77.8%);2例未检出HLA-Ⅰ类抗体和HPA抗体。31例HPA抗体阳性中,患者血小板膜糖蛋白抗体鉴定结果为,GPⅡb/Ⅲa抗体26例(72.2%),GPⅠa/Ⅱa抗体23例(63.9%), GPⅠb/Ⅸ抗体19例(52.8%),GPⅣ抗体17例(47.2%)。抗体阳性患者中女性21例,男性15例;女性HLA抗体阳性率高于男性,女性HPA抗体阳性率低于男性,但差异无统计学意义。结论 PTR患者中血小板抗体以HLA-Ⅰ类抗体合并HPA抗体为主。     

新乡地区HPA基因分型供者库在免疫性血小板输注无效中的应用研究

目的建立新乡地区已知HPA-1-18基因型的无偿机采血小板供者库,为临床血小板输注无效(PRT)患者提供HPA相合的血小板,方法建立PCR-SSP检测HPA-1-18基因型检测方法;采用固相凝集法对52名PRT患者,做血小板同种抗体筛查;应用HLA抗体特异性试剂盒检测患者血清群体反应性抗体;对血小板同种抗体筛查阳性患者,采用已知HPA基因型的标准谱血小板做抗体鉴定,并对其进行HPA基因分型;采取HPA抗体无对应抗原的供者血小板进行输注。结果成功检测出150名无偿血小板捐献者HPA-1-18基因型。在52例PRT病例中,检出血小板同种抗体23例(阳性率44%),其中5例鉴定为抗-HPA(21.7%),分别为HPA-3a 2例;HPA-15b 3例;其余HLA抗体阳性18例。结论对PRT患者采用HPA基因型相合的方法进行输注取得临床效果。     

血小板输注无效患者血小板特异性糖蛋白抗体表达的实验研究

目的探讨血小板输注无效(PTR)患者血小板特异性糖蛋白抗体的表达情况。方法采用ELISA方法检测56名临床上确诊为PTR患者的血小板特异性糖蛋白抗体、应用PCR方法检测其血小板特异性抗原(HPA)1-6,15基因分型。结果 56名PTR患者检出血小板特异性糖蛋白抗体,8例表达阳性(占14.3%),包括血小板特异性糖蛋白GPⅡb/Ⅲa阳性7例,GPⅠa/Ⅱa阳性1例、GPⅠb/Ⅰx阳性1例、GPⅣ阳性1例。结合8例患者的抗体检测反应格局和HPA抗原基因型结果分析抗体的特异性为:4例存在抗-HPA3b、3例存在抗-HPA3a、1例存在抗-HPA5b。结论反复输血的血小板输注无效患者,应选择HPA抗原相匹配的血小板供者,以改善血小板输注效果。     

92例血小板输注无效的原因探讨

目的了解血小板输注无效的原因,以便做好预防工作。方法采用ELISA方法对92名血小板输注无效的患者进行血小板特异性抗体检测及HLA抗体检测,并调查其临床情况。结果 92名患者由免疫因素导致的PTR为61例(占66.3%),其中HLA抗体引起的血小板输注无效最常见(占40.2%)。在患者血清中多表现为GPⅡb/Ⅲa和GPⅠa/Ⅱa特异性糖蛋白抗体阳性。结论血小板输注无效的主要原因为免疫因素。因此提倡配合性血小板输注,以提高其治疗效果。     

Flow cytometric detection of platelet-reactive antibodies and application in platelet crossmatching

Background: Alloimmunization against HLA or platelet antigens can cause refractoriness to platelet transfusions in multiply transfused patients. Crossmatching of platelet concentrates is effective in overcoming this problem. Study Design and Methods: A flow cytometric assay was used for simultaneous detection of lymphocyte-reactive and platelet-reactive antibodies in a single sample using fluorescein isothiocyanate-labeled anti-IgG. This assay was compared with the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay in selected sera containing HLA and platelet antibodies. In a further study, this assay was compared with lymphocytotoxicity test results from thrombocytopenic patients, for whom platelet concentrates were ordered. The results of both assays were then correlated with the 1-hour corrected count increment, with a corrected count increment greater then 7500 considered as an adequate transfusion response. Results: The results of the MAIPA and flow cytometric assay in detecting platelet-reactive antibodies correlated well (p<0.0001, r = 0.84). The sensitivity and specificity of the flow cytometric assay in detecting platelet-reactive antibodies were 94.7 and 96.3 percent, when the MAIPA assay was taken as a reference. In unselected sera from patients, the sensitivity and specificity of the flow cytometric assays were, respectively, 72.7 and 91.7 percent in detecting lymphocyte- reactive antibodies and 70.6 and 77.7 percent in detecting platelet- reactive antibodies, when the lymphocytotoxicity test was used as a reference. With regard to an adequate transfusion response, the sensitivities and efficiencies were 20.0 and 82.1 percent, 33.3 and 84.3 percent, and 70.0 and 88.6 percent for the lymphocytotoxicity test and the lymphocyte-reactive and platelet-reactive flow cytometric assays, respectively. Conclusion: Flow cytometric crossmatching appears to be an effective method of detecting platelet-reactive antibodies that may affect the success of platelet transfusions. This procedure is well-suited for routine conditions and can be performed within 2 hours.     

Platelet transfusion refractoriness caused by a mismatch in HLA-C antigens

BACKGROUND: HLA-C antigens have been thought to be of little significance in determining the efficacy of platelet transfusions. However, six alloimmunized patients were encountered who were refractory to platelet transfusions because of anti-HLA-Cw3, -Cw3, -Cw7, or -Cw8. STUDY DESIGN AND METHODS: Between 1995 and the present, 88 patients with hematologic malignancies became refractory to random-donor platelet transfusions due to HLA antibodies. HLA-A- and HLA-B-compatible platelet transfusions were successful in boosting platelet levels with 82 of the patients. This study concerns the remaining six HLA-immunized patients who were refractory to HLA-A- and HLA-B-compatible platelet transfusions. The response to the platelet transfusions was assessed by calculating both 1- and 24-hour posttransfusion CCIs for each transfusion. RESULTS: The average CCI(1 hour) and CCI(24 hours) in all patients were 20.0 and 12.8 for HLA-A-, HLA-B-, and HLA-C-compatible transfusions and were 1.4 and 1.2 for HLA-A- and HLA-B-compatible but HLA-C-incompatible transfusions, respectively (p < 0.001). CONCLUSION: These findings clearly indicate that matching of the HLA-C antigens is also required in some alloimmunized patients to obtain the effectiveness of platelet transfusions.     

Pre-transfusion screening for platelet-reactive antibodies.

We retrospectively compared the cost of platelet concentrates (PCs) used for patients whose serum had already been screened for platelet-reactive antibodies with the cost for patients whose serum was examined after the commencement of treatment using platelets. On the basis of 774 patients' data, the mean cost of PCs for the latter group of patients ($5562) was higher than that for the former group ($2547). Screening beforehand ensured a prompt supply of specific PCs, and costs were suppressed by the avoidance of multiple transfusions. We conclude that screening for platelet-reactive antibodies followed by administration of crossmatch-negative PCs appears to be both clinically and economically advantageous.     

Platelet-reactive HLA antibodies associated with low posttransfusion platelet increments:a comparison between the monoclonal antibody-specific immobilization of platelet antigens assay and the lymphocytotoxicity test

BACKGROUND: Platelet-reactive HLA antibodies are a major reason for low posttransfusion platelet increments. The clinical importance and value of the test systems for their in vitro determination is still controversial. STUDY DESIGN AND METHODS: A prospective analysis of HLA antibodies was performed in sera obtained once a week for at least 4 consecutive weeks from 55 patients (female/male, 28/27; age: median, 49 years; range, 18-69) undergoing intensive chemotherapy and in need of prophylactic platelet transfusions. All sera (n = 330) were analyzed by the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay and by the standard lymphocytotoxicity test (LCT). RESULTS: In the MAIPA, 24.5 percent of sera (81/330) obtained from 22 patients contained HLA antibodies. These were detected significantly more often by the MAIPA assay than by the LCT (24.5% vs. 8.2%). Fifty-five sera (20 patients) were positive in the MAIPA assay only. In 15 patients, HLA antibodies were transient. In 3 patients, HLA antibodies were detected earlier by the MAIPA assay than by the LCT. Significantly more sera obtained at the time of low posttransfusion platelet increments were positive in MAIPA alone, rather than in both MAIPA and the LCT (44% vs. 17%). CONCLUSION: The MAIPA assay is more sensitive than the standard LCT in detecting platelet-reactive HLA antibodies. These MAIPA-positive/LCT-negative HLA antibodies affect the posttransfusion platelet increment.     

Heterogeneity of antibody response to human platelet transfusion.

To study the antibody response to human platelet transfusions, nine thrombocytopenia patients with bone marrow failure were given 6 U (3X10(11)) of random platelet concentrates twice a week. Before transfusion, none of the patients had preexisting antibodies detectable with lymphocytotoxicity, platelet aggregation, or capillary leukoagglutination techniques. After receiving 18-78 U of platelets, they became refractory to further transfusions of random platelets and alloantibodies were detectable. Two patterns of antibody response could be identified. In three patients, the sera were not lymphocytotoxic with a panel of standard cells in which all the known HLA antigens in the first and second series were represented at least once. Yet, they caused platelet aggregation with 30, 24, and 60%, respectively, of a donor population studied. The aggregating activities were inhibited by antihuman IgG but not by antihuman IgA or antihuman IgM antiserum. The aggregating antibodies could be absorbed out with donor platelets but not lymphocytes or granulocytes. Antibodies from two of these patients aggregated platelets of their respective siblings matched for both HLA haplotypes. Transfusion of platelets from these two siblings did not increase the platelet count while platelets obtained from aggregation-negative donors did. The sera from the remaining six patients were lymphocytotoxic with 15-100% of the panel of standard cells. They also had aggregating antibodies, which could be absorbed out by both platelets and lymphocytes, suggesting that they were HLA antibodies. These data suggest that the development of platelet-specific antibodies may play an important role in the immunological rejection of isologous platelets, and should be considered in the selection of donors for patients who are refractory to platelets from random donors.     

Posttransfusion purpura following bone marrow transplantation

BACKGROUND : Thrombocytopenia is a major cause of morbidity and hospital expense following bone marrow transplantation. Platelet transfusions in these patients are frequently complicated by the recipient's development of antibodies to HLA class I antigens. When these patients become refractory to the transfusion of HLA-matched platelets, the recipient's platelet antigen phenotype must be determined, to ensure that donor platelets will be phenotypically compatible. Cases of alloimmunization to HPA-1a and HPA-1b resulting in refractoriness to transfused platelets and the subsequent development of a posttransfusion purpura-like syndrome are reported. CASE REPORTS: In the first case, a 43-year-old woman with Stage IV infiltrating ductal breast cancer presented to the hospital for a transplant of autologous peripheral blood stem cells. After the transplant, her platelet count remained less than 10 × 10⁹ per L, despite daily platelet transfusions, including HLA-matched platelets. Fourteen days following the transplant, her serum was found to contain anti-HPA-1a. Initially, the patient was refractory to the transfusion of HPA-1a-negative platelets, but after treatment with intravenous immunoglobulin, she had transient increases in posttransfusion platelet counts. She was also treated with a staphylococcal protein A immunoadsorption column and has not had any such subsequent refractoriness. Her genotype has been found, by use of allele-specific oligonucleotide hybridization with white cell DNA, to be HPA-1b/1b. The second case involved a 32-year-old woman with chronic myelogenous leukemia who received an unrelated-donor marrow transplant. Three years later, her CML recurred, and she was treated with interferon-alpha. Four months afterward, she experienced interferon-alpha-induced thrombocytopenia and the interferon therapy was discontinued. She received 12 platelet transfusions in 20 days, but none was effective. Antibodies specific for HLA antigens and HPA-1b were detected, and three HLA-matched, HPA-1b-negative apheresis platelet components were given, but without effect. Two days after treatment with methylprednisolone (1 g intravenously) and prednisone (2 mg/kg/day orally), her platelet count was 26 × 10⁹ per L, and after 8 more days, it was 102 × 10⁹ per L, without further transfusions. She was found to be homozygous for HPA-1a (HPA-1a/1a). CONCLUSION : Anti-HPA- 1a and anti-HPA-1b can cause refractoriness to platelet transfusions in bone marrow transplant patients. Testing for platelet-specific antibodies should be considered in all patients who are refractory to HLA-matched platelets.     

Platelet transfusions in the neonatal intensive care unit:factors predicting which patients will require multiple transfusions

BACKGROUND: Previous studies suggest that recombinant thrombopoietin (rTPO) will increase platelet production in thrombocytopenic neonates. However, the target populations of neonates most likely to benefit should be defined. Studies suggest that rTPO will not elevate the platelet count until 5 days after the start of treatment. Therefore, the neonates who might benefit from rTPO are those who will require multiple platelet transfusions for more than 5 days. This study was designed to find means of prospectively identifying these patients. STUDY DESIGN AND METHODS: A historic cohort study of all patients in the neonatal intensive care unit (NICU) at the University of Florida who received platelet transfusions from January 1, 1997, through December 31, 1998, was conducted. RESULTS: Of the 1389 patients admitted to the NICU during the study period, 131 (9.4%) received platelet transfusions. Seventeen were treated with extracorporeal membrane oxygenation and were excluded from further analysis. Of the remaining 114 patients, 55 (48%) received one transfusion and 59 (52%) received more than one transfusion (21 had >4). None of the demographic factors examined predicted multiple platelet transfusions. However, two clinical conditions did; liver disease and renal insufficiency. Neonates who received one platelet transfusion had a relative risk of death 10.4 times that in neonates who received none (p = 0.0001). Neonates who received >4 platelet transfusions had a risk of death 29.9 times that in those who received no transfusions (p = 0.0001). CONCLUSION: NICU patients with liver disease or renal insufficiency who receive one platelet transfusion are likely to receive additional transfusions. Therefore, these patients constitute a possible study population for a Phase I/II rTPO trial.     

Glanzmann''s thrombasthenia; assessment of the response to platelet transfusions

The response to platelet transfusions was studies in two patients with Glanzmann's thrombasthenia. Antibodies to platelets were detected in one patient who had failed to respond to platelet transfusions, and bled during and after surgery despite fresh whole blood transfusions. The other patient had no detectable antiplatelet antibodies, exhibited improved platelet function when normal platelets were added to her platelet-rich plasma and experienced a favorable response to platelet transfusions during major surgery. These cases demonstrate the importance of antiplatelet antibodies as a determinant of a patient's response to platelet transfusion, the value of this therapy in qualitative platelet disorders, and the potential usefulness of in vitro studies to predict the outcome of platelet transfusions in such patients.     

Detection of drug-dependent, platelet-reactive antibodies by antigen- capture ELISA and flow cytometry

The effectiveness of flow cytometry in the detection of drug-dependent, platelet-reactive antibodies was investigated. In studies of seven sera known to contain quinine- or quinidine-dependent, platelet-reactive antibodies, flow cytometry was 5 to 10 times more sensitive in detecting drug-dependent antibodies (DDAbs) than the 51Cr release assay, antigen-capture enzyme-linked immunosorbent assay (ELISA), and indirect immunofluorescence microscopic assay. With flow cytometry, DDAbs could be detected at drug concentrations as low as 0.1 microM, or less than one-tenth the level required with other methods. Antigen-capture ELISA was not as sensitive as flow cytometry in DDAb detection, but it did allow identification of the DDAbs' target molecules. With this assay, five of the seven DDAbs recognized both the glycoprotein Ib/IX (GPIb/IX) and glycoprotein IIb/IIIa (GPIIb/IIIa) complexes, while the remaining two sera reacted only with GPIb/IX. Of 44 consecutive patients who developed thrombocytopenia while taking quinidine, DDAbs were detected by flow cytometry in 11 (25%), more than twice the number detected by other methods. In one patient who developed thrombocytopenia while taking trimethoprim/sulfamethoxazole, DDAbs could be detected only by flow cytometry. It can be concluded that flow cytometry is highly sensitive in detecting DDAbs and allows their detection at pharmacologic concentrations of the drug. Most quinidine-dependent antibodies recognize at least two different glycoprotein complexes in the platelet membrane.     

Clinical factors influencing posttransfusion platelet increment in patients undergoing hematopoietic progenitor cell transplantation—a prospective analysis

BACKGROUND: Platelet transfusion refractoriness remains problematic in the management of patients who have undergone hematopoietic progenitor cell transplantation. Bone marrow transplantation itself is reported to be a relevant factor hampering efficient platelet transfusions. However, a prospective analysis assessing factors affecting platelet transfusion efficacy in the setting of hematopoietic progenitor cell transplantation has yet to be conducted. STUDY DESIGN AND METHODS: To identify factors independently influencing platelet transfusion efficacy after hematopoietic progenitor cell transplantation, a prospective study was performed to determine the effectiveness of platelet transfusions by estimating posttransfusion (16-hour) corrected count increments (CCI) in 42 consecutive patients (26 who received allogeneic transplants and 16 who received autologous transplants) with 439 available platelet transfusions. RESULTS: The mean CCI and percentage of CCI <4500 for all transfusions were 6161.1 +/− 7775.2 per microL and 42.1 percent, respectively. Multiple linear regression analyses revealed high total bilirubin, total body irradiation, high serum tacrolimus, and high serum cyclosporin A to be major factors independently predicting a lower CCI. HLA antibodies with restricted specificity and platelet antibodies were detected transiently in 17 and 14 percent of the patients, respectively. The presence of these antibodies was not, however, associated with a poor response to platelet transfusions. CONCLUSION: Platelet transfusion efficacy in hematopoietic progenitor cell transplant recipients is markedly influenced by clinical factors specific to the procedure as well as those already recognized in other settings. Alloimmunization is not, however, a major factor associated with a poor response to platelet transfusions after this procedure.