title: Clinical and laboratory correlates of platelet alloimmunization and refractoriness in the PLADO trial.
abstract: OBJECTIVE
  Platelet alloimmunization and refractoriness to platelet transfusion are complications of platelet transfusion therapy. The platelet dose (PLADO) trial, as the largest prospective randomized trial of prophylactic platelet therapy to date, afforded an opportunity to analyse these two issues.
  
  
  METHODS
  PLADO patient records were examined for evidence of platelet alloimmunization, defined as an increase in HLA Class I panel-reactive antibodies (PRA) to ≥20%, and clinical refractoriness, defined as two consecutive ≤4 h posttransfusion corrected platelet count increments (CCI) of <5000. Multivariate logistic regression, restricted to platelet-transfused subjects who received exclusively either in-process leucoreduction apheresis or whole blood-derived (WBD) leucocyte-reduced platelets, compared the frequency of these outcomes by platelet unit and patient characteristics.
  
  
  RESULTS
  Forty of 816 evaluable platelet-transfused patients (5%) became alloimmunized during the trial. Prior pregnancy, chemotherapy only compared to progenitor cell transplant, and low platelet dose - all were associated with significantly higher rates of alloimmunization. Among 35 alloimmunized patients evaluated for refractoriness, 8 (23%) had two consecutive CCI < 5000/μl. Regardless of alloimmunization status, CCIs < 5000/μl were observed following 17% of platelet transfusions. Among 734 patients receiving at least two platelet transfusions, two consecutive CCIs of ≤5000 occurred in 102 (14%).
  
  
  CONCLUSIONS
  The incidence of new platelet alloimmunization was low in the PLADO study, but follow-up was at most 30 days. Alloimmunization was present in only 8 of 102 (8%) of observed cases of refractoriness, suggesting that other causes of poor posttransfusion increments are frequent.
authors.affiliation: University of Washington, Seattle, WA, USA. hessj3@uw.edu.
authors.forename: J R
authors.initials: JR
authors.lastname: Hess
authors.affiliation: New England Research Institutes, Watertown, MA, USA.
authors.forename: F L
authors.initials: FL
authors.lastname: Trachtenberg
authors.affiliation: New England Research Institutes, Watertown, MA, USA.
authors.forename: S F
authors.initials: SF
authors.lastname: Assmann
authors.affiliation: Institute for Transfusion Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Triulzi
authors.affiliation: Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Kaufman
authors.affiliation: Institute for Transfusion Medicine, University of Pittsburgh, Pittsburgh, PA, USA.|University of Iowa College of Medicine, Iowa City, IA, USA.
authors.forename: R G
authors.initials: RG
authors.lastname: Strauss
authors.affiliation: New England Research Institutes, Watertown, MA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Granger
authors.affiliation: University of Washington, Seattle, WA, USA.|Bloodworks Northwest (formerly the Puget Sound Blood Center), Seattle, WA, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Slichter
mesh_terms: D000906:Antibodies / Q000097:blood; D001327:Autoimmune Diseases / Q000209:etiology*; D001781:Blood Component Removal; D001792:Blood Platelets / Q000166:cytology / Q000276:immunology*; D002986:Clinical Trials as Topic; D005500:Follow-Up Studies; D018380:Hematopoietic Stem Cell Transplantation; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D006801:Humans; D007938:Leukemia / Q000628:therapy; D016015:Logistic Models; D010976:Platelet Count; D017713:Platelet Transfusion / Q000009:adverse effects*; D014184:Transplantation, Homologous
chemical_list: D000906:Antibodies; D015395:Histocompatibility Antigens Class I
keywords: clinicaltrials.gov number NCT00128713; prophylactic platelet transfusion; response to platelet transfusion; transfusion medicine hemostasis clinical trials network