Complement (C1q) Binding to HLA Antibodies in a Solid-phase Immunoassay and Clinical Effect on Platelet Transfusion
Condition: Thrombocytopenia; Platelet Transfusion Refractoriness
MeSH terms: Thrombocytopenia
Study type: Observational

Summary: 
      Background:

      Platelets are blood cells that help blood clot. Some people have what is called
      thrombocytopenia. This means they have a low blood platelet count. They need platelet
      transfusions very often. Human leukocyte antigen (HLA) alloimmunization occurs for a lot of
      these people. They become refractory. This means their platelet levels no longer increase
      after transfusions. Researchers want to study a procedure that detects HLA antibodies. They
      want to test how well it predicts how a person will respond to a transfusion. They want to
      see if it does this better than the procedure that is usually used.

      Objective:

      To study the effect of C1q-binding of Class I HLA antibodies on platelet refractoriness in
      people who get platelet transfusions. To test if this method better predicts response to
      platelet transfusion than the IgG solid phase immunoassay method.

      Eligibility:

      People enrolled on protocols 11-C-0136, 08-H-0156, 03-C-0277, 01-C-0157, or 01-C-0129 who:

      Agreed to have their specimens and data used for future research

      Had Class I HLA antibodies detected by the IgG method

      Had one or more platelet transfusions at NIH after the first positive HLA IgG antibody result

      Design:

      For each participant, researchers will look at a small portion of their archived plasma
      sample. The samples were left over from prior HLA antibody tests.

      Participants samples will be analyzed. They will be tested to see if C1q-binding HLA
      antibodies are present. This will be done by solid phase immunoassay. Results will be
      compared with the past results of the IgG method.

      Participants data will be stored in database that s protected by password.
    

Detailed description: 
      Human leukocyte antigen (HLA) alloimmunization is common in patients undergoing frequent
      platelet transfusion, and is the most important cause of immune platelet refractoriness.
      Management strategies in HLA alloimmune platelet-refractory patients include transfusion with
      HLA-matched or crossmatched platelets; however, in broadly-sensitized patients, or in
      patients with uncommon HLA types, antigen-negative or epitope compatible donors may be
      difficult to find.

      The Luminex immunoglobulin (Ig)G single-antigen-bead (SAB) solid phase immunoassay is now
      commonly used to detect HLA antibodies. However, an assay that specifically detects
      C1qbinding to HLA antibodies has been reported to identify a clinically relevant subset of
      HLA antibodies in solid organ transplantation; one group has studied the utility of this
      assay in platelet transfusion of HLA-alloimmunized platelet refractory patients. We intend to
      evaluate the ability of this C1-binding immunoassay to predict response to platelet
      transfusion in HLA alloimmune patients.
    

Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Keywords: Alloimmunization; Refractoriness; Corrected Count Increment; HLA-Compatible; Natural History