***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    ***EXAMPLES*** 
    Input: Alloantibodies against HLA antigens can be reduced by applying leukodepletion to transfusions . Because the importance of immunological and nonimmunological causes of poor platelet transfusion results using leukodepleted transfusions is not clear , we conducted a prospect i ve study in an unselected patient population receiving leukodepleted transfusions . In 97 patients with hematological malignancies , 181 r and om leukodepleted platelet transfusions  were studied for immunological causes of poor platelet transfusion results by calculating the odds ratio of four different screening tests for a low platelet recovery . Nonimmune causes were also studied by calculating the odds ratio of the most prevalent nonimmune causes for a low platelet recovery . No single screening test showed an association with recovery after 1 and 16 h following a platelet transfusion . The combination of a positive enzyme-linked immunosorbent assay ( ELISA ) and platelet immunofluorescence test ( PIFT ) or a combination of a positive lymphocyte immunofluorescence test ( LIFT ) and PIFT , demonstrating an association with a low platelet recovery after 16 h , was present in 2 % of all platelet transfusions . Of nonimmune causes , splenomegaly and storage time of platelets for more than 3 days were associated with low platelet recovery after 1 h and 16 h of being present in 29 % and 47 % of all platelet transfusions , respectively . Immunological causes account for a small proportion of poor platelet transfusion results compared to nonimmunological causes in a nonselected patient population receiving leukodepleted transfusions Seventy-nine  platelet transfusions to 73 thrombocytopenic patients with cancer were analyzed to determine whether a platelet count obtained one hour after transfusion could help differentiate between alloimmunization and other clinical factors that result in rapid platelet destruction . These transfusions were selected because 18- to 24-hour increments were inadequate in response to fresh , r and om donor platelets . A corrected count increment ( Cl ) ( Cl=[posttransfusion count-pretransfusion count]Xbody surface area [ sq m]/platelets transfusedX10 ' ' ) at one hour of 10X103/microliter or greater was associated with absence of lymphocytotoxic antibody , whereas increments of less than 10X103/microliter were generally associated with high levels of strongly cytotoxic antibody .  HLA-matched transfusions produced no improvement in increments when the previous one-hour Cl had been 10X103/microliter or greater , whereas in the other group significantly better increments were obtained . A one-hour posttransfusion count is a simple test that correlates well with the presence of antibody against HLA antigens , is valuable in predicting the need for HLA-matched platelets , and helps avoid wasteful , empirical use of such transfusions 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 were determined after 522 single‐donor platelet transfusions given to 43 patients persistently refractory to pooled r and om‐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 < 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 posttransfusion platelet recovery A variety of patient and product-related factors influenced the outcome of 6379 transfusions given to 533 patients in the Trial to Reduce Alloimmunization to Platelets ( TRAP ) . Responses measured were platelet increments , interval between platelet transfusions , and platelet refractoriness . Patient factors that improved platelet responses were splenectomy and increasing patient age . In contrast , at least 2 prior pregnancies , male gender , splenomegaly , bleeding , fever , infection , disseminated intravascular coagulation , increasing height and weight , lymphocytotoxic antibody positivity , an increasing number of platelet transfusions , or receiving heparin or amphotericin were associated with decreased posttransfusion platelet responses . Platelet factors that were associated with improved platelet responses were giving ABO-compatible platelets , platelets stored for 48 hours or less , and giving large doses of platelets while ultraviolet B ( UV-B ) or gamma irradiation decreased platelet responses . However , in alloimmunized lymphocytoxic antibody-positive patients , the immediate increment to UV-B-irradiated platelets was well maintained , whereas all other products showed substantial reductions . Refractoriness to platelet transfusions developed in 27 % of the patients . Platelet refractoriness was associated with lymphocytotoxic antibody positivity , heparin administration , fever , bleeding , increasing number of platelet transfusions , increasing weight , at least 2 pregnancies , and male gender . The only factors that reduced platelet refractoriness rates were increasing the dose of platelets transfused or transfusing filtered apheresis platelets R and omized controlled trials have shown a reduction in platelet alloimmunization and refractoriness in patients with acute leukemia ( AL ) with the use of poststorage leukoreduction of blood products . Universal prestorage leukoreduction ( ULR ) of red cell and platelet products has been performed in Canada since August 1999 . We conducted a retrospective analysis of 13 902 platelet transfusions in 617 patients undergoing chemotherapy ( CT ) for AL or stem cell transplantation ( SCT ) before ( n = 315 ) and after ( n = 302 ) the introduction of ULR .  Alloimmunization was significantly reduced ( 19 % to 7 % , P < .001 ) in the post-ULR group . Alloimmune platelet refractoriness was similarly reduced ( 14 % to 4 % , P < .001 ) . Fewer patients in the post-ULR group received HLA-matched platelets ( 14 % vs 5 % , P < .001 ) . Alloimmunization and alloimmune refractoriness in the 318 patients who were previously pregnant and /or transfused were also reduced after ULR ( P = .023 and P = .005 , respectively ) . In a Cox regression model , the 3 independent factors that predicted for alloimmune refractoriness were nonleukoreduced blood products ( relative risk [ RR ] , 2.2 [ 95 % CI , 1.2 - 4.3 ] ) , a history of pregnancy and /or transfusion ( RR , 2.3 [ 95 % CI , 1.3 - 4.2 ] ) , and receipt of 13 or more platelet transfusions ( RR , 6.0 [ 95 % CI , 2.4 - 15.3 ] ) . In conclusion , ULR reduces alloimmunization , refractoriness , and requirements for HLA-matched platelets when applied as routine transfusion practice to patients receiving CT or SCT A critical factor limiting the availability of histocompatible platelet transfusions for alloimmunized , thrombocytopenic patients is the large pool of HL‐typed donors needed to procure platelets perfectly matched for HLA antigens . We have , therefore , investigated the effectiveness of platelets obtained from donors having lesser degrees of histocompatibility . In 421 transfusions administered to 59 alloimmunized patients who were refractory to “ r and om donor ” platelets  , it was found that platelets mismatched for 1 or 2 “ cross‐reactive ” HLA antigens were in most instances as effective in increasing circulating platelet levels as perfectly matched platelets . A significant number of patients also responded to platelets from donors selectively mismatched for non‐cross‐reactive HLA antigens . The latter group had a significantly reduced frequency of the antigen HLA‐A2 ( 13 % ) in comparison to the total patient population ( 49 % ) . Use of donors whose HLA antigens are serologically cross‐reactive with those of alloimmunized patients provides approximately 10 times as many prospect i ve donors as does selection based on matching for HLA and simplifies the procurement of hemostatically effective platelets for such patients Alloantibody tests demonstrate immunological causes of insufficient increments in r and om 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 r and om 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 r and om 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 Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more Repeated  platelet transfusion to thrombocytopenic patients frequently induce anti HLA antibodies , which are responsible for transfusion refractoriness . As the transfused platelet suspensions usually contain 15 - 30 % of the leukocytes originally present in the blood , it is not known whether these antibodies are raised by the platelets or by the contaminating leukocytes in the platelet suspensions . In the mouse , pure platelet suspensions are not able to induce a primary antibody response , as measured by the NIH test and the indirect immunofluorescence test on platelets and leukocytes , despite repeated injections . However , when the platelet suspensions are contaminated with leukocytes ( 10(3 ) or more/injection ) an antibody response is induced . This response is higher than the response indiced by an equal amount of leukocytes alone . As in man the use of leukocyte poor platelets postpones the development of refractoriness to r and om platelets it is concluded that transfusions with leukocyte free platelets will probably prevent immunization against the HLA antigens This study describes a novel application of HLAMatchmaker to determine platelet compatibility in 16 alloimmunized patients with aplastic anemia refractory to r and om donor platelet transfusions .  HLAMatchmaker is a software algorithm that predicts HLA compatibility by identifying immunogenic epitopes represented by amino acid triplets in antibody-accessible regions of human leukocyte antigen ( HLA ) molecules and determines the number of triplet mismatches ( TMMs ) and highly immunogenic triplet mismatches ( HIMMs ) . Corrected count increments ( CCIs ) and molecular HLA typing were available for 523 transfusions .  Conventional compatibility assessment based on cross-reactive group ( CREG ) determination was not predictive of transfusion outcome . Low HIMMs and TMMs numbers were associated with a higher likelihood of satisfactory ( CCIs > or = 8) compared with unsatisfactory ( CCIs < 8) outcomes ( median HIMMs = 4 vs 6 , p2 value < .001 ; median TMMs = 11 vs 13 , p2 value < .001 ) . Although receiver operator characteristic curves revealed that HIMMs or TMMs number are not powerful predictors of individual transfusion outcome , a threshold of at least 3 HIMMs or at least 9 TMMs appeared to be associated with successful transfusions . Triplet-matched transfusions were successful , regardless of CREG matching . Our data vali date HLAMatchmaker for platelet transfusions and demonstrate its potential to refine and exp and donor selection for HLA-alloimmunized patients We implemented a prospect i ve study to evaluate platelet transfusion utilization , re source use , and costs in a tertiary care hospital over a 6‐month period . All hospitalized patients receiving platelet transfusions between July and December 1996 were followed prospect ively to determine platelet use and costs . Clinical and financial data were collected , evaluated , and compared to identify trends in re source utilization based on admitting service and platelet‐refractory status . One thous and nine hundred forty‐four platelet units were transfused to 245 hospitalized patients ( 
    Output:
    
HLA-matched PLTs did not reduce alloimmunization and refractoriness rates beyond that offered by leukoreduction , and utilization was not consistently improved .
HLA-matched PLTs led to better 1-hour posttransfusion count increments and percentage of PLT recovery in refractory patients ; however , the effect at 24 hours was inconsistent .