Complement (C1q) Binding to HLA Antibodies in a Solid-phase Immunoassay and Clinical Effect on Platelet Transfusion

Study Overview
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Brief Summary
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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
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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.

Official Title
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Complement (C1q) Binding to HLA Antibodies in a Solid-Phase Immunoassay and Clinical Effect on Platelet Transfusion

Conditions
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Thrombocytopenia, Platelet Transfusion Refractoriness

Participation Criteria
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Eligibility Criteria
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INCLUSION CRITERIA: Class I HLA antibodies detected by the IgG solid phase immunoassay method Greater than or equal to 1 episode of platelet transfusion at NIH after the first positive HLA IgG antibody result EXCLUSION CRITERIA: 1) Hyperproliferative thrombocytopenia

Ages Eligible for Study
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Minimum Age: 3 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| 1<br>Previously selected HLA-alloimmunized platelet refractory, clinical, patients. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Corrected count increment after platelet transfusion | Corrected Count Increment | Retrospective | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Alloimmunization, Refractoriness, Corrected Count Increment, HLA-Compatible, Natural History