An evaluation of crossmatching, HLA, and ABO matching for platelet transfusions to refractory patients

Refractoriness occurs in many patients receiving multiple platelet transfusions. We used a sensitive ELISA assay to assess the utility of crossmatching HLA-A,B matched single donor platelets in 51 consecutive, typical refractory patients. Of the 222 transfusions evaluated at 1 to 4 hours posttransfusion, only 17 of 54 (31%) with positive crossmatches had corrected platelet count increments of greater than or equal to 7,500/microL. In contrast, 95 of 168 (57%) of those with negative crossmatches had such increments (P less than .001). Regardless of the results of the crossmatch, HLA-A,B, and ABO matching had independent influences on transfusion outcome. The median corrected 1- to 4-hour increment for crossmatch negative transfusions was 13,300/microL for A/BU grade matches, 9,700 for BX, and 7,800 for C. Increments were 10,000/microL for ABO-identical transfusions and 5,900 for transfusions of platelets ABO incompatible with the recipient's plasma antibodies. When the donor platelets were ABO compatible, but the donor plasma contained ABO antibodies to the recipient's platelets, the increment was intermediate (8,200/microL). The most important factor in predicting platelet survival was the crossmatch, followed by HLA-A,B and ABO, each having independent predictive value. These data demonstrate that the predictive value of a negative crossmatch may be considerably less than that reported in previous studies with stable, less ill patients. In typical refractory patients, there appear to be mechanisms of platelet destruction that are related to HLA-A,B and ABO but are not detected with current crossmatch methods. We hypothesize that soluble plasma HLA-A,B and ABO antigens contribute to the destruction of donor and sometimes recipient platelets by an immune complex or other "innocent bystander" mechanism. With our crossmatching technique, HLA-A,B and ABO match grades remain relevant to platelet transfusion therapy in some refractory patients.     

Platelet transfusion improves clot formation and platelet function in severely thrombocytopenic haematology patients

Prophylactic platelet (PLT) transfusion is a common practice in severely thrombocytopenic patients that reduces mortality, but responses to platelet transfusions are variable and difficult to predict in individual patients. In this prospective study, we evaluated the outcome of PLT transfusions in 40 patients with haematological malignancies, linking corrected count increment (CCI) to clot formation and agonist-induced platelet activation after transfusion. The CCI was highly variable between patients and 34% showed no response (1-h CCI < 7,5). Short time since the last PLT transfusion and extended storage time of the PLT product were linked to poor transfusion response, while patient sex, C-reactive protein or the number of chemotherapy cycles prior to transfusion did not influence transfusion outcome. High CCI and good PLT responsiveness to agonist stimulation predicted efficient clot formation in rotational thromboelastometry, but transfusion did not restore poor PLT function in patients to the level of healthy controls. Our study provides new insights into factors affecting PLT transfusion outcome in haematology patients with severe thrombocytopenia, and suggests that the thrombocytopenic environment, or disease-associated factors, may hamper platelet responsiveness.     

The value of alloantibody detection in predicting response to HLA-matched platelet transfusions

Alloantibody tests demonstrate immunological causes of insufficient increments in random platelet transfusions. The value of a positive or negative test result in predicting the outcome of human leucocyte antigen (HLA)-matched transfusions in patients refractory to leucodepleted random platelet transfusions has not been assessed. We retrospectively evaluated the outcome of the first HLA-matched platelet transfusion in 72 patients with haematological diseases in two ways: first, the strategy according to which the patient was selected for HLA-matched platelet transfusions was analysed. The strategies were: (i) results of alloantibody tests were not available, (ii) a positive alloantibody test, (iii) a negative alloantibody test. Secondly, the outcome of the first HLA-matched transfusion was investigated relative to the results of alloantibody tests, irrespective of the decision strategy. No significant association was found between the decision strategy and the outcome of the first HLA-matched platelet transfusion. Positive alloantibody tests, however, predicted a better outcome of the first HLA-matched platelet transfusion (P = 0.04 and P = 0.03 after 1 and 16 h respectively). In patients refractory to random platelet transfusions, positive alloantibody tests predicted a better outcome of HLA-matched platelet transfusions. Patients with negative alloantibody tests, however, may benefit from HLA-matched platelet transfusions.     

Lymphocytotoxic antibody is a predictor of response to random donor platelet transfusion

The transfusion records of 189 patients with acute leukemia were analyzed to correlate lymphocytotoxic antibody (LCTAb) levels with response to a series of random-donor platelet transfusions (Tx). Twenty-one patients were studied twice at times of different LCTAb levels. All transfusions were given when patients were clinically stable without disseminated intravascular coagulation, bleeding, temperature > 101°F, or splenomegaly. The mean 1-hr and 24-hr corrected count increments (CCI) for all patients with negative LCTAb were 16,100 and 12,000, and values for patients with positive LCTAb were 5,600 and 2,600 (P < 0.0005). Thirteen patients had intermediate LCTAb (10–20%) and a variable response to Tx. Of the 137 patients with negative LCTAb levels 106 (77%) had good mean CCI of > 10,000 at 1 hr and > 7,500 at 24 hr following transfusion. In contrast of 60 patients with positive LCTAb (> 20% cytotoxicity), 53 (88%) had poor CCI of < 10,000 at 1 hr and < 7,500 at 24 hr after transfusion. Only 4 patients with positive LCTAb had a good response to random donor platelets at both 1 and 24 hrs. Eighteen patients had negative LCTAb with a high 1-hr and low 24-hr CCI. Thirteen of these had a history of positive LCTAb and in 9 there was an anamnestic rise following transfusion. Nine of 137 patients had negative LCTAb with low 1-hr and 24-hr CCI. LCTAb is highly predictive of response to random donor platelets. Cytotoxicity to > 20% of tested lymphocytes virtually precludes a good CCI at 1 and 24 hr.     

Efficacy of transfusion of platelet concentrates obtained by manual pooling or by semiautomated pooling of buffy-coats: a retrospective analysis of count increment, corrected count increment and transfusion interval

Background and Objective  The preparation of platelet concentrates from pooling buffy-coats can be done manually or semiautomatically with the OrbiSac BC System. The objective of this study was to compare the clinical outcome of platelet transfusions prepared by these two methods in terms of 1-h count increment (1-h CI), 1-h corrected count increment (1-h CCI) and transfusion interval.
Materials and Methods  Platelet transfusions were identified retrospectively for inclusion in the control group (manual pooling) or the test group (automated pooling). Transfusion outcome variables were 1-h CI, 1-h CCI and transfusion interval. The impact of 16 patient- and platelet concentrate-related variables on transfusion efficacy was investigated by multiple regression analysis.
Results  The database analysed consisted of 205 control transfusions given to 36 patients and 219 test transfusions given to 36 patients. Mean platelet content and mean 1-h CI were statistically higher in the test group when compared to the control group ( P <  0·05), but mean 1-h CCI and transfusion interval were not. Multiple regression analysis resulted in models explaining 13% of the variance of 1-h CI, 8% of the variance of 1-h CCI and 17% of the variance of transfusion interval ( P <  0·05).
Conclusion  There are no significant differences between the two preparation methods regarding the clinical outcome of platelet transfusions, as the difference in 1-h CI is explained by differences in platelet content.     

A flow cytometric platelet immunofluorescence crossmatch for predicting successful HLA matched platelet transfusions

Platelet crossmatching may provide a useful way of selecting donors for effective platelet transfusions in patients refractory to random donor platelet concentrates due to alloimmunization. We assessed the predictive value of a flow cytometric platelet immunofluorescence crossmatch test for the outcome of HLA matched platelet transfusions in a group of alloimmunized patients. Platelet immunofluorescence (PIFT) crossmatches were performed for 104 HLA-matched platelet transfusions administered to 30 patients. A negative PIFT crossmatch correctly predicted a successful platelet transfusion (1 h post-transfusion platelet recovery >20%) in 56/75 (75%) cases. We also considered non-immunological factors that, in combination with alloimmunization, might have contributed to an unsuccessful transfusion result, i.e. fever, septicaemia, splenomegaly, disseminated intravascular coagulation and bleeding. The predictive value of a negative PIFT crossmatch was better when these non-immunological factors were absent [48/59 (81%) correct predictions] than when these factors were present [8/16 (50%) correct predictions] (P=0.01; chi-square test). The effect of ABO incompatibility between donor and recipient on the predictive value of the PIFT crossmatch was also analysed. Positive PIFT crossmatches occurred more frequently in ABO incompatible donor–recipient combinations [in 18/28 (64%) cases] than in ABO-compatible donor–recipient combinations [in 11/76 cases (14%)] (P<0.001, chi-square test). Successful platelet transfusions were observed on 53/76 (70%) occasions in ABO compatible transfusions as compared to 16/28 (57%) in ABO incompatible transfusions. This difference was not statistically significant (P=0.23; chi-square test). Consequently, a negative PIFT crossmatch appeared to be non-predictive for the transfusion outcome in cases of ABO incompatibility between donor and recipient. We conclude that the PIFT crossmatch for platelet donor selection in addition to matching for HLA antigens, is predictive for the outcome of ABO compatible transfusions in alloimmunized recipients and prediction levels are increased when non-immunological causes for platelet refractoriness are absent.     

Evaluation of four methods for platelet compatibility testing

Four platelet compatibility assays were performed on serum and platelet or lymphocyte samples from 38 closely HLA-matched donor/recipient pairs involved in 55 single-donor platelet transfusions. The 22 patients studied were refractory to transfusions of pooled random-donor platelets. Of the four assays (platelet suspension immunofluorescence, PSIFT; 51Cr release; microlymphocytotoxicity; and a monoclonal anti-IgG assay, MAIA), the MAIA was most predictive of platelet transfusion outcome (predictability, 74% for one-hour posttransfusion platelet recovery and 76% for 24-hour recovery). The only other assay to reach statistical significance was the PSIFT (63% predictability for one-hour posttransfusion recovery). The degree of HLA compatibility between donor and recipient (exact matches v those utilizing cross-reactive associations) was unrelated to the ability of the MAIA to predict transfusion results. The MAIA may be capable of differentiating HLA antibodies, ABO antibodies, and platelet-specific antibodies responsible for failure of HLA-matched and selectively mismatched single-donor platelet transfusions.     

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 <5×10⁹/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.     

Factors influencing the transfusion response to HLA-selected apheresis donor platelets in patients refractory to random platelet concentrates

Immune and nonimmune causes of platelet refractoriness were evaluated in a group of patients receiving HLA-selected single-donor platelet transfusions. During a 1-year observation period, 1 h and 24 h platelet recoveries wre determined after 522 single-donor platelet transfusions given to 43 patients persistently refractory to pooled random-donor platelet transfusions. 72% of patients tested ultimately developed lymphocytotoxic antibodies suggesting they were alloimmunized. When significant lymphocytotoxic antibodies were demonstrable in these patients, HLA well-matched platelet transfusions consistently produced good transfusion responses. In contrast, patients without lymphocytotoxic antibodies had clinical factors that adversely affected transfusion outcome (P less than 0.0001). Fever and splenomegaly markedly reduced 1 h post-transfusion platelet recoveries, while sepsis compromised the 24 h platelet recovery. Overall, the presence of any clinical factor was most likely to reduce 1 h platelet recovery, while donor-recipient HLA incompatibilities correlated best with poor 24 h post-transfusion platelet recovery. A platelet crossmatch test predicted the transfusion response when non-immune clinical factors were absent.     

A specific assay for anti-HLA antibodies: application to platelet donor selection

Alloimmunization to donor class I HLA antigens represents a major obstacle to successful platelet transfusion therapy. It is desirable to distinguish alloimmunization from nonimmunologic causes of poor platelet survival to assess the need for HLA-matched, single-donor platelets. We describe a new in vitro assay for anti-HLA antibodies and report its application to the problem of platelet crossmatching. In contrast to previously described crossmatch techniques, the immunobead assay is specific for anti-HLA antibodies. The assay was used to evaluate 51 single-donor platelet transfusions given to seven patients from 35 different donors. Recipient plasma was assayed for antibodies directed against HLA antigens present on donor platelets. A one-hour posttransfusion corrected count increment of greater than or equal to 7,500 was considered a successful outcome. Twenty-nine of 33 (87.9%) transfusion episodes associated with a negative immunobead assay had successful outcomes. The four unsuccessful transfusions were associated with potential nonimmunologic causes of poor platelet survival. Only two of 18 (11.1%) episodes associated with a positive assay had successful outcomes. Only one unsuccessful transfusion episode was associated with a negative immunobead assay and a positive radiolabeled antiglobulin test result, which suggested that isolated alloantibodies to antigens other than class I HLA antigens are not a common cause of platelet refractoriness. Platelets stored in suspension at 4 degrees C or frozen in liquid nitrogen were found suitable for crossmatch testing.     

Preparation of Leucocyte-Poor Platelet Concentrates from Buffy Coats

To study survival and function of leukocyte-poor platelet concentrates (lp-PC) prepared from buffy coats, random platelet transfusions requested for thrombocytopenic patients were evaluated. The lp-PC issued were stored at 22 degrees C for either 1, 3 or 5 days before transfusion. From 31 transfusions, posttransfusion corrected count increments (CCI), corrected for body surface (m2) and divided by number of platelets transfused (1011), were calculated. The mean +/- SEM of the 1-, 24- and 48- hour CCI was 12.2 +/- 0.45, 11.2 +/- 0.51 and 8.8 +/- 0.58, respectively. No significant differences in CCI 24 h after transfusion were observed for 1p-PC stored for 1, 3 or 5 days. Hemostatic activity was observed in all 9 evaluable patients. It is concluded that platelets from 1p-PC survive well in patients, regardless of storage for 1, 3 or 5 days and that the platelets are hemostatically active after transfusion.     

Comparative assessment of prophylactic transfusions of platelet concentrates obtained by the PRP or buffy-coat methods,in patients undergoing allogeneic hematopoietic stem cell transplantation

ABSTRACT

Objectives: Whole blood-derived platelet concentrates can be obtained by the platelet-rich plasma (PRP-PCs) or the buffy-coat (BC-PCs) method. Few studies have shown that BC-PCs display lower in vitro platelet activation, but scarce information exists regarding transfusion efficacy. We have performed a retrospective study assessing platelet transfusion in patients undergoing allogeneic hematopoietic cell transplantation (AHCT) in our clinic, before and after the implementation of BC-PCs.

Methods: We reviewed clinical records corresponding to 70 PRP-PCs and 86 BC-PCs prophylactic transfusions, which were performed to 55 AHCT patients. Transfusion efficacy was assessed by the 24-h post-transfusion corrected count increment (24-h CCI) and bleeding events. Clinical factors affecting transfusion outcome were also investigated.

Results: Clinical characteristics and the total number of platelet transfusions were similar among groups. Mean donor exposure was 5.8 and 5.0 in each single PRP-PCs and BC-PCs transfusion, respectively (p?<?0.01). The 24-h CCI was significantly higher in patients transfused with BC-PCs than in those receiving PRP-PCs (8.3[2.7–13.4] vs. 4.7[1.3–8.1]; p?<?0.01). Independent predictors of poor platelet transfusion response included diagnosis other than acute leukemia (HR 8.30; 95% CI 1.96–35.22; p?=?0.004), splenomegaly (HR 8.75; 95% CI 2.77–27.60; p?<?0.001), graft versus host disease prophylaxis different from cyclosporine A and methotrexate (HR 3.96; 95% CI 1.55–10.14; p?=?0.004) and PRP-PCs transfusion (HR 4.54; 95% CI 1.72–12.01; p?=?0.002). There were no differences between both groups regarding the bleeding events.

Conclusion: In the AHCT setting, we hypothesize that BC-PCs transfusion, when compared to PRP-PCs, results in higher CCI and reduced donor exposure, but provides no significant benefit regarding bleeding outcome.     

Identification of alloimmunized patients: use of radiolabeled allogeneic platelet kinetic measurements and platelet antibody tests

In a group of stable, nonthrombocytopenic leukemia patients awaiting bone marrow transplantation, results of paired allogeneic radiolabeled platelet kinetic measurements were correlated with the results of several different platelet and lymphocytotoxic antibody tests to determine which parameters could be used to identify patients who were alloimmunized to platelets. Seven patients with acute leukemia who had been transfused during induction therapy were used as the test group, and, as a control group, five untransfused patients with chronic myelogenous leukemia were also studied. Concurrent fibrinogen survival measurements were performed in all patients to assess whether hemostatic factor consumption (ie, disseminated intravascular coagulation) was present. Allogeneic platelet survival measurements were reduced from normal in all 12 study patients. In 8 of 12 patients, fibrinogen and platelet survival measurements were comparably reduced, suggesting disease-related platelet consumption. In four heavily transfused patients with acute leukemia, allogeneic platelet survivals were markedly reduced to less than or equal to 2.1 days, compared with the 3.5- to 7.4-day platelet survival measurements found in the other eight patients. The disproportionately short platelet survivals compared with fibrinogen survival measurements in these four patients, combined with documented positive antibody tests to their donors' platelets in the three patients with evaluable tests, suggested that these patients had become alloimmunized to platelets because of their prior transfusions. There was substantial concordance between the two radiolabeled allogeneic donor platelet survival measurements performed in each of these patients, suggesting that host rather than donor factors have a major influence on transfusion outcome (r = .93, P less than .001). The platelet cross-match tests, using the radiolabeled protein Staph A assay combined with the IgG enzyme-linked immunosorbent assay test, had the best correlation with the posttransfusion recovery and survival of the donors' platelets.     

Intravascular and total body platelet equilibrium in healthy volunteers and in thrombocytopenic patients transfused with single donor platelets

Instrument platelet counts used in corrected count increment (CCI) and percent platelet recovery (PPR) formulas presume the transfused platelets are in equilibrium during the first hour after platelet transfusion. The timing of the pre-transfusion count affects CCI results, and we postulate that timing of CCI post transfusion affects CCI results. Platelet equilibrium using indium-111 platelet transfusions has not been reported. Platelet redistribution was studied in 16 healthy volunteers and 12 thrombocytopenic patients by generally infusing less than 72-hr stored single-donor platelets along with an aliquot of indium-111-labeled platelets by intravenous push. Counts were measured at 10, 15, 20, 60, and 120 min, and 24, 48, 72 hr along with continuous body scanning for 2 hr in healthy volunteers, and static organ scanning in patients and volunteers. Results indicated transfused platelets do not reach intravascular equilibrium for 60 min post-infusion and that the 10-min count cannot detect platelet refractoriness. However, total body equilibrium varies considerably between normal volunteers and thrombocytopenic patients. It is recommended to continue with the 1-hr post transfusion count. Am. J. Hematol. 58:165–176, 1998. © 1998 Wiley-Liss, Inc.     

Optimal dosing and triggers for prophylactic use of platelet transfusions.

Despite the reliance on platelet transfusion support in patients receiving myeloablative therapy, controversies surround platelet transfusion practices. These include the appropriate platelet dose and the threshold at which prophylactic platelet transfusions will be most effective. These issues bear directly on patient outcome (donor exposure and bleeding complications), cost effectiveness of transfusion, and maintenance of adequate platelet inventories. This review examines the recent studies that have taken on the task of resolving these questions in order to provide optimal platelet transfusion guidelines. Studies now have convincingly demonstrated that a 10,000/microL threshold for prophylactic platelet transfusion is safe and effective in uncomplicated thrombocytopenic patients. Although platelet dosages vary, in general, smaller doses are both effective and inventory-sparing in the more complicated inpatient setting, while larger platelet doses allow for an increased transfusion interval for chronic outpatient support.     

Optimizing platelet transfusion therapy

Platelet transfusions are widely used. Prophylactic transfusions are employed in severely thrombocytopenic patients without evidence of bleeding, but no randomized trial data prove the safety or efficacy of this approach. Randomized trials have demonstrated the equivalence of transfusion triggers of 10,000 and 20,000/microl for prophylactic transfusions. The former threshold is potentially safer for the patient, conservative of donor resources and leads to lower costs, with perhaps a slightly greater risk of minor hemorrhage. Randomized trials have demonstrated the equivalence of pheresis or whole blood-derived platelet transfusions. The former present a lower risk for infectious agents, and the latter are less expensive and a more efficient use of limited donor resources. Randomized trials prove that leukoreduced and ABO identical platelet transfusions reduce the risks of HLA alloimmunization and platelet transfusion refractoriness (both leukoreduction and ABO matching), transfusion reactions (leukoreduction) and CMV transmission (leukoreduction). Leukoreduction and ABO matching of platelet transfusions also have been associated in preliminary observational studies with reduced morbidity and mortality in surgical patients and reduced infections in patients with leukemia. These results require further investigation. Future challenges include (1) determining the best approach to bacterial contamination of platelets, whether by detection methods or pathogen inactivation and (2) determining the threshold for prophylactic platelet transfusions in thrombocytopenic patients undergoing surgery or invasive procedures.     

The expression of IgG allotypes on platelets and immunization to IgG allotypes in multitransfused thrombocytopenic patients

We investigated whether the platelet-membrane surface carries IgG allotypic antigens and whether these determinants may be important in platelet transfusion therapy. Using a hemagglutination inhibition assay, we showed that the G1m IgG allotypes (a, x, f) and K1m and K3m light-chain allotypes are expressed on the surface of platelets, whereas G3m allotype antigenic determinants were not detectable. In 146 multitransfused thrombocytopenic patients, 35 (24%) patients were found to have antiallotypic antibodies. To study the effect of antiallotypic antibodies on platelet transfusion outcome, patients received platelet transfusions from donors, either positive or negative for the IgG allotype to which patients were immunized. Of the 19 antigen-positive and 19 antigen-negative platelet transfusions given, respectively, the mean platelet count increments at 1 hour were 8,402 +/- 6,402 +/- 6,721 (1 SD) and 9,799 +/- 5,559 (1 SD) P less than .2. Transfusion reactions were not more common when antigen-positive platelet transfusions were given. Despite the presence of IgG allotypic determinants on platelets, allotypic antibodies do not decrease platelet transfusion recovery. Furthermore, passive administration of plasma containing IgG allotypes to patients with antiallotypic antibodies does not lead to innocent bystander-mediated platelet destruction.     

Predictive value of enzyme-linked immunoassay platelet crossmatching for transfusion of platelet concentrates to alloimmunized recipients

Some evidence has shown that platelet crossmatching is useful in multitransfused patients with hypoplastic bone marrows who are refractory to platelet therapy through alloimmunization. Several immunoglobulin binding assays other than enzyme-linked immunospecific assay (ELISA) have been studied previously. We performed 51 ELISA crossmatches on six patients receiving single donor platelets. One bone marrow transplant patient receiving 33 single donor HLA matched (related and unrelated) was also studied. Effectiveness of transfusion was closely monitored by patient evaluation and corrected platelet count increment (CCI) at 1-2 and 18-24 hours posttransfusion. We found the ELISA method very sensitive, specific, and predictive, 85, 96, and 95.6% respectively in the 51 crossmatches studied in six patients with either leukemia, solid tumors, or aplastic anemia. However, variation existed among individual recipients, with sensitivity ranging from 70-100%. The distribution of true positives and negatives and false positives and negatives in the 33 crossmatches performed in the bone marrow transplant patient differed significantly (chi 2 = 101.2; P less than 0.001) from single donor recipients. The specificity in the 51 crossmatches on the six patients was also significantly different from the 33 crossmatches performed in the bone marrow transplant (96 vs 74%). This suggests individual variation occurs as well as differences in diseases and bone marrow suppressive agents affecting platelet crossmatching.     

A restrictive platelet transfusion policy allowing long-term support of outpatients with severe aplastic anemia

The threshold for prophylactic platelet transfusions in patients with hypoplastic thrombopenia generally recommended in the standard literature is 20,000 platelets/microL. A more restrictive transfusion policy may be indicated in patients with chronic severe aplastic anemia (SAA) in need of long-term platelet support. We evaluated the feasibility and safety of a policy with low thresholds for prophylactic transfusions (相似文献   

Alloimmunization after Leukocyte-Depleted Multiple Random Donor Platelet Transfusions

In a prospective study we investigated the development and the course of alloimmunization after leukocyte-depleted red cell and multiple random donor platelet transfusions in 335 patients. Of these 335 patients, who had a negative antibody screening on admission and a negative transfusion history, 69 (21%) developed either transient (n = 18) or permanent (n = 51) lymphocytotoxic antibodies, but only 31 patients (9%; 95% confidence limits 6-12%) developed multispecific alloantibodies necessitating HLA-matched platelet transfusions. There was no difference with regard to the development of antibodies and platelet refractoriness between leukemia patients receiving cytostatic treatment and patients with aplastic anemia receiving prednisone and antithymocyte globulin. Females with previous pregnancies developed platelet refractoriness with an increased incidence (Chi 2 13.38; p less than 0.001) compared to females without previous pregnancies, males, and children.